Honeywell T874 Users Manual 60 2485 Multistage Thermostats And Q674 Subbases
T874 60-2485
T874 to the manual 90e2c8a4-2323-4664-ab75-47d879b91c07
2015-01-23
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T874 Multistage Thermostats and Q674 Subbases PRODUCT DATA FEATURES • T874 Thermostat has silent, dust-free mercury switches operated by coiled bimetal elements. • Heat anticipator(s) are adjustable or fixed cooling anticipator(s) are fixed. • Individual heat and cool levers and scales (most models) for temperature setting located on top of thermostat case. • Cover thermometer on most T874 Multistage Thermostat models. • Locking cover and locking lever screws available for T874 Multistage Thermostats. • Versaguard™ Thermostat Guard or custom key lock thermostat guards available for T874 Multistage Thermostats. • T874 Thermostat requires a Q674 Subbase. APPLICATION These thermostats and subbases provide low voltage control of multistage heating and cooling systems, including heat pump systems. • Q674 Subbase provides system and fan switching, wiring terminals and mounting base for T874 Multistage Thermostat. • Adapter plate available for mounting Q674 on wall or horizontal outlet box. • Light-emitting diodes (LEDs) located on subbase for easy reference. • Up to three stages each of heating and cooling control possible. • Models with setpoint restrictions and locking cover with no thermometer available for Department of Defense (DoD) and other special applications. • Outdoor reset used on some models to improve thermal performance. Contents Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Understanding Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Cross Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 ® U.S. Registered Trademark Copyright © 2001 Honeywell • All Rights Reserved 60- 2485- 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SPECIFICATIONS Tradeline Models IMPORTANT The specifications given in this publication do not include normal manufacturing tolerances. Therefore, this unit may not exactly match the listed specifications. This product is tested and calibrated under closely controlled conditions, and some minor differences in performance can be expected if those conditions are changed. T874 THERMOSTAT • T874 TRADELINE models provide staged heat and/or cool operation. See Table 1. Table 1. Heating and Cooling Stages. Models A B C D E F Heating Stages 1 1 2 2 — 2 Cooling Stages 1 2 1 2 2 — Super Tradeline®/Tradeline® Models • T874A-F are standard models. SUPER TRADELINE controls offer features not available on TRADELINE or standard models, and are designed to replace a wide range of Honeywell and competitive controls. TRADELINE FEATURES: • TRADELINE package with cross reference label and special instruction sheet. • T874A,C model available with factory stops for DoD applications. • T874A,C model available with adjustable temperature locking stops. TRADELINE models are selected and packaged to provide ease of stocking, ease of handling, and maximum replacement value. Specifications of SUPER TRADELINE and TRADELINE controls are the same as those of standard models except as noted below. Super Tradeline Models T874 THERMOSTAT T874D Thermostat. Provides two stages of heating and two stages of cooling. Use with Q674A-F Subbases. Y594D (T874D/Q674E/TG504A) Thermostat/Subbase/key lock cover package. Provides two stages of heating and two stages of cooling. Includes a key lock cover for setpoint protection. Y594G (T874G/Q674F) Thermostat/Subbase package for heat pump. Provides two stages of heating and one stage of cooling. Automatic changeover in heat or cool mode. Available in beige or Premier White® color. Y594R (T874R/Q674L) Thermostat/Subbase package for heat pump. Provides two stages of heating and one stage of cooling. Manual changeover in heat or cool mode. Available in beige or Premier White® color. SUPER TRADELINE FEATURES: • SUPER TRADELINE package with cross reference label and special instruction sheet. • SUPER TRADELINE model supplied with locking lever and locking cover accessories. • Includes adjustable temperature locking stops. • T874D replaces T874A-F TRADELINE or standard models. Q674 SUBBASE Q674 switching subbases provide system and fan switching. See Table 2. Table 2. System and Fan Switching. Q674 System Fan A Heat-Auto-Cool Auto-On B Heat-Off-Cool Auto-On C Off-Auto Auto-On D None None E Off-Heat-Auto-Cool Auto-On F Em. Ht.-Off-Heat-Auto-Cool Auto-On G Off-Auto None J Em. Ht.-Auto-Off Auto-On L Em. Ht.-Heat-Off-Cool Auto-On TRADELINE FEATURE: • TRADELINE package with cross reference label and special instruction sheet. • Q674A-E,G are standard (non-heat pump) models. Q674F,J,L are heat pump models. ORDERING INFORMATION When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number. If you have additional questions, need further information, or would like to comment on our products or services, please write or phone: 1. Your local Home and Building Control Sales Office (check white pages of your phone directory). 2. Home and Building Control Customer Relations Honeywell, 1885 Douglas Drive North Minneapolis, Minnesota 55422-4386 (800) 328-5111 In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9. International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A. 60-2485—8 2 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Standard Models Thermometer Range: 42° to 88°F (6 to 31°C) T874 THERMOSTATS Changeover Differential: 4°F (2°C) minimum between heating and cooling (5°F [3°C] on T874W). Levers can be set apart for greater separation. Models: See Table 3. Interstage Differential: Standard Models: Mechanical differential is 1°F (0.6°C) between heating or cooling stages; operating differential is approximately 1.9°F (1°C) between stages in heating or cooling. Special Models: See Table 3. Electrical Rating: 24 to 30 Vac. Switching: Coiled bimetal elements operate mercury switches. Temperature Adjustment: Heating and cooling setting levers, with separate scales located on top of thermostat base. Common lever for heating and cooling on T874R; one cooling lever on T874E,V; and one heating lever on T874F,Q. Finish: Beige or Premier White® finish. Mounting Means: T874 Multistage Thermostat mounts on Q674 Subbase. Subbase mounts horizontally on wall or outlet box. Mounts on vertical outlet box with optional 193121A Adapter Plate Assembly. Dimensions: See Fig. 1. Temperature: Scale Range: 42° to 88°F (6° to 31°C) standard; optional ranges available. THERMOSTAT MOUNTED ON SUBBASE SUBBASE SIDE FRONT 3/8 (10) 5-5/8 (143) HEAT 50 60 70 80 3-9/32 (83) 50 60 70 80 COOL 1-1/2 (38) 50 60 70 80 3-7/16 (87) 3-1/2 (89) FAN AUTO ON FAN OFF EM. HT. HEAT AUTO COOL 1-7/8 (48) AUTO ON OFF EM. HT. HEAT AUTO COOL 5-1/8 (130) 2-3/16 (56) M5849 Fig. 1. T874 Thermostat and Q674 Subbase dimensions in in. (mm). Optional Specifications (T874 Only): Temperature scale ranges are 40° to 75°F (4° to 24°C) heating and 75° to 90°F (24° to 32°C) cooling with stop; 44° to 68°F (7° to 20°C) heating, 80° to 86°F (27° to 30°C) cooling; 6° to 29°C (43° to 85°F) Celsius scale; 3° to 22°C (38° to 72°F) and 26° to 32°C (78° to 90°F) cooling with stop. Nonadjustable factory-added stop limits heating setpoint to 72°F (22°C) maximum and cooling setpoint to 78°F (26°C) minimum. OEM customer personalization. Locking cover and locking lever (see Thermostat Accessories). Thermostat cover without thermometer. Adjustable locking temperature stops. Voltage heat anticipation for first or second stage heat or both. See Table 3. Fast cycling on heating stage(s) for electric heat applications. C815A Outdoor Thermistor for improved performance on specified models. Thermostat Accessories: Locking Cover and Locking Lever Assembly: Part no. 194559R with thermometer; 194559S without thermometer. See Fig. 2. Includes cover, screws, and Allen wrench for locking cover. The screws must be used to assure proper operation. Adjustable Lever Stop: Part no. 4074ECK; includes lever stop and screws. Universal Versaguard™ Thermostat Guard: Includes wallplate, ring base, guard cover, tumbler lock, two keys and optional Honeywell logo insert. Double-wall construction provides extra measure of tamper-resistance. Tamperresistant lock; key cannot be removed without being in locked position. Vents in guard base allow airflow for optimum thermostat performance. See form 68-0104 for more information. — TG511A1000: Clear cover. — TG511B1008: Opaque cover. — TG511D1004: Painted steel (off-white) cover. See Fig. 2. 3 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Key Lock Cover: Part no. TG504A replaces existing T874 cover. Mounts on T874 base and covers thermostat settling levers and subbase switches. Includes LED window and two keys. Should not be used with 193121A Adapter Plate. — — TG504A1025: Blank face, internal thermometer. TG504A1033: External thermometer. See Fig. 2. TG504A1033 Key Lock Cover with External Thermometer 194559R Locking Cover with Thermometer Allen Wrench TG511D1004 Includes Painted Steel Cover, Opaque Base and Wallplate Fig. 2. T874 Thermostat accessories. Table 3. T874 Thermostat Specifications. Anticipation System Stages Models and Options T874A—Standard and TRADELINE®. — 72°F/78°F (22°C/26°C)setpoint stops with locking cover. — Adjustable anticipator set 0.4A. — Adjustable locking temperature stops (TRADELINE®). — 72°F/78°F (22°C/26°C) setpoint stops with locking cover, no thermometer (for DoDa). Heating (Adj) Replaces Applications Heat Cool Other Stage 1 T872A Standard 1 1 — Stage 2 Stage 1 Stage 2 0.1-1.2A — 0-1.5A — — 0-1.2A 0-1.0A 0-1.5A — 0-1.2A 0-1.0A 0-1.2A 0-1.0A — — T874B—Standard and TRADELINE. T872B Standard 1 2 — 0.1-1.2A T874C—Standard and TRADELINE. — 72°F/78°F (22°C/26°C)set stops with locking cover, no thermometer (for DoDa). — 12°F (7°C) differential between H1 and H2 stages (T874C1125). T872C Standard 2 1 — 0.1-1.2A 0.1-1.2A — Fast cycling. 0.120.6A T874D—Standard and SUPER TRADELINE®. — Adjustable locking temperature stops (SUPER TRADELINE). T872D Standard 2 2 — T874E—Standard and TRADELINE. T872E 2-Stage Cool — 2 — T874F—Standard and TRADELINE. — Locking cover. T872F 2-Stage Heat 2 — — a b c d e f g Department of Defense. Changeover stage operates with heating. Fixed voltage type anticipation. Changeover stage operates with heating; a secondary changeover is provided in cooling switch. Provides night setback used with standard T874 and timer-operated remote switching. Manual changeover stage—use Q674B,L subbase. Changeover stage operates with cooling.Q674 Subbases 60-2485—8 4 Cooling (Fixed) 0.120.6A 0.1-1.2A 0.1-1.2A — — 0.1-1.2A 0.1-1.2A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES — Fast cycling. T874G—Heat pump, cool changeover, with fast cycling. 0.120.6A 0.120.6A 0-1.0Ac 0.1-1.2A Electric Heat T872G Heat Pump or Standard 2 1 1b — Fixed anticipator for H2. — 0.1-1.5A — Fast cycling. T874H—Use with Q674C. 0-1.0A 0.120.6A T872H Heat Pump or Standard 1 1 1b 0-1.0Ac — 0-1.0A — T874J—Heat pump. None Heat Pump 2 1 2d 0-1.0Ae 0-1.5Ac 0-1.0Ac — T874K—Heat pump. None Heat Pump 2 1 1b 0.1-1.2A 0-1.5Ac 0-1.5A — T874L—Heat pump. None Heat Pump 2 1 — 0.1-1.2A 0.1-1.2A 0-1.5A — T872N Heat Pump 2 1 b 1 0.1-1.2A 0.1-1.2A 0-1.0A — 2 1 — 0.1-1.2A 0.1-1.2A 0-1.5A — e — 0.1-1.2A — — — T874N—Heat pump, heat changeover. T874P—Heat pump. None Heat Pump T874Q—Night setback heating. T872Q Standard 1 — T874R—Heat pump. T872R f Heat Pump 2 1 — 0-1.5Ac 0.1-1.2A 0-1.5A — T874S—Two-speed compressor heat pump. None Heat Pump 2 2 1g 0-1.2Ac 0-1.2Ac 0-1.2A 0-1.0A T874V—Standard. None Standard — 1 — — — 0-1.5A — T872W Heat Pump or Standard 3 2 — T874W—Heat pump and standard. — Night setback heating. a b c d e f g 0-1.2Ab 0-1.2Ac,d 0-1.2A 0-1.0A Department of Defense. Changeover stage operates with heating. Fixed voltage type anticipation. Changeover stage operates with heating; a secondary changeover is provided in cooling switch. Provides night setback used with standard T874 and timer-operated remote switching. Manual changeover stage—use Q674B,L subbase. Changeover stage operates with cooling.Q674 Subbases Models: See Table 4. Mounting: Designed to mount horizontally on an outlet box or the wall. Adapter plate assembly available for mounting on a vertical outlet box (see Subbase Accessory). Electrical Ratings: Switch Contacts: 2.5A at 30 Vac (7.5A inrush). LED Lights (Optional): 30 Vac. Finish: Dark brown or gray. Switches: Two slide switches (one switch on Q674G and K; no switches on Q674D) operated by levers. Switch position is shown on scaleplate. Dimensions in in. (mm): 3-1/2 (89)height; 5-5/8 (143) width; 5/16 (8) depth. See Fig. 1. Table 4. Q674 Subbase Specifications. Switch Positions Models and Options Replaces Application System Fan Use With Q674A—Standard and TRADELINE®. — Indicator LEDs. Q672A Standard HEAT-AUTO-COOL AUTO-ON T874A-D Q674B—Standard and TRADELINE. Q672B Standard HEAT-OFF-COOL AUTO-ON — Provision for fan relay operation from Heat Pump external fan switch (isolate G terminal). OVERRIDE-HEAT- — Indicator LEDs. Q674C—Standard and TRADELINE. AUTO-ON T874P OFF-COOL Q672C — Indicator LEDs. Standard OFF-AUTO AUTO-ON T874A-H,W Heat Pump OVERRIDE-AUTO- AUTO-ON T874K,L,N Standard None None T874A-F OFF Q674D—Standard and TRADELINE. — For use when subbase switching is not required. T874A-D T874G,H,L,R Q672D 5 T874P 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Q674E—Standard and TRADELINE. Q672E Standard OFF-HEAT-AUTOCOOL AUTO-ON T874A-D Q674F—Two LED models. — EM.HT. light. Q672F Heat Pump OFF-EM.HT.-HEATAUTO-COOL AUTO-ON T874C,D,G,N,S OFF-COOL-AUTOHEAT-EM.HT. AUTO-ON — Provision for AUTO fan operation in EM.HT. Q674G—O and B terminals. Q672G Standard OFF-AUTO None T874A-F Q674J—Provision for AUTO fan operation Q672J Heat Pump EM.HT.-AUTO-OFF AUTO-ON T874A,D,G,J in EM.HT. — Provision for outdoor thermistor. Q674K—Standard. Q672K Q674L—Provision for AUTO fan operation in EM.HT. Q672L Standard Heat Pump — Indicator LEDs. EM.HT.-ON-OFF AUTO-ON SUPL.HT.-ON-OFF AUTO-ON OFF-HEAT-AUTOCOOL None OFF-WOOD-WOOD/ OIL-OIL None EM.HT.-HEAT-OFFCOOL AUTO-ON SUPL.HT.-HEATOFF-COOL AUTO-ON T874F T874R,W Q674N—Standard. Q672N Evaporative Cooler EVAP-COOL-OFFHEAT AUTO-ON T874C Q674P—Standard. Q672P Heat Pump SUPL.HT.-HEATCOOL AUTO-ON T874G Q674Q—Standard. None Fan Coil HEAT-OFF-COOL LO-MED-HION T874A Q674R—Standard. — International symbols. None Fan Coil OFF-COOL LO-HICONT. T874V Q674S—Indicator LED. None Standard HEAT-COOL None T874C Optional Specifications (Q674 Only): Models available with up to four LEDs; for example, LEDs can show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and LOCKOUT. See Fig. 3. System switching marked HEAT-OFF/RESET-COOL for systems requiring impedance relay reset. Available on Q674B only. G terminal isolated on heating to provide fan relay operation from external low voltage fan switch (Q674B only). Auto fan operation on both heat and cool. T874 Thermostat with One Setpoint Lever L terminal is used for system monitoring devices. Common R terminal for heating/cooling. Changeover in cool or heat mode for heat pumps. Auto fan in EM.HT. for heat pumps. Subbase Accessory: 193121A Adapter Plate Assembly for mounting on vertical outlet box. Assembly includes adapter ring and cover plate. Use to cover wall marks from replaced thermostat. T874 Thermostat with Separate Heating and Cooling Levers Fig. 3. Heating, cooling levers and system LED indicators. 60-2485—8 6 Q674 Subbase with Four LEDs T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES MERCURY NOTICE This control contains mercury in a sealed tube. Do not place control in the trash at the end of its useful life. If this control is replacing a control that contains mercury in a sealed tube, do not place your old control in the trash. Contact your local waste management authority for instructions regarding recycling and the proper disposal of this control, or of an old control containing mercury in a sealed tube. If you have questions, call the Honeywell Customer Response Center at 1-800-468-1502. INSTALLATION When Installing this Product… 1. 2. 3. 4. Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition. Check the ratings given on the product to make sure the product is suitable for your application. Installer must be a trained, experienced service technician. After installation is complete, check out product operation as provided in these instructions. — concealed pipes and chimneys. — unheated (uncooled) areas such as an outside wall behind the thermostat. Mount Subbase The subbase can be mounted on a vertical outlet box, horizontal outlet box or directly on the wall. 1. If the subbase is mounted on a vertical outlet box, order Honeywell part no. 193121A Adapter Assembly. See Fig. 4. The assembly includes an adapter ring, two screws and a cover plate to cover marks on the wall. Install the ring and cover plate on the vertical outlet box. NOTE: For a wall installation, hold subbase in position and mark holes for anchors. See Fig. 5. Wall anchors must be obtained from local hardware store. Be careful that the wires do not fall back into the wall opening. Set aside subbase. Drill four 3/16 in. (4.8 mm) holes and gently tap anchors into the holes until flush with the wall. 2. Pull wires through the cover plate (if used) and subbase cable opening. See Fig. 6. 3. Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws. Level the subbase using a spirit level, see Fig. 7, and firmly tighten subbase mounting screws. The subbase mounting holes provide for minor out-of-level adjustments. VERTICAL OUTLET 1 BOX MOUNTING SCREWS (2) CAUTION Hazardous Voltage. Can damage heating/cooling system. 1. Disconnect power supply before beginning installation to prevent electrical shock or equipment damage. 2. Do not short across coil terminals on relay. This can burn out thermostat heat anticipator. 3. To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires as close as possible to the subbase. 4. Do not overtighten thermostat captive mounting screws because damage to subbase threads can result. COVER PLATE 2 ADAPTER RING 2 1 HORIZONTAL OUTLET BOX THERMOSTAT IMPORTANT An incorrectly leveled thermostat will cause the temperature control to deviate from setpoint. It is not a calibration problem. SUBBASE AT HE Location THERMOSTAT COVER OL CO 50 50 60 70 60 70 80 80 SUBBASE MOUNTING SCREWS (2) Install the thermostat about 5 ft (1.5m) above the floor in an area with good air circulation at average temperature. CAPTIVE MOUNTING SCREWS (2) Do not mount the thermostat where it can be affected by: — drafts or dead spots behind doors, in corners or under cabinets. — hot or cold air from ducts. — radiant heat from the sun, fireplace, or appliances. 1 NOT INCLUDED WITH UNIT. 2 ACCESSORY PART AVAILABLE (193121A). 50 60 70 80 M6009 Fig. 4. Installing Q674 Subbase on outlet box. 7 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES All wiring must comply with local electrical codes and ordinances. WALL IMPORTANT Use 18 gauge, solid-conductor wire whenever possible. If using 18 gauge stranded wire, no more than 10 wires can be used. Do not use larger than 18 gauge wire. WIRES THROUGH WALL OPENING WALL ANCHORS (2) M926 Follow equipment manufacturer wiring instructions when available. To wire subbase, proceed as follows: 1. Connect the system wires to the subbase as shown in the applicable diagram. A letter code is located near each terminal for identification. Typical terminal designation and wiring connections are listed in Table 5. The terminal barrier permits straight or wraparound wiring connection. See Fig. 7. The subbase can require one or more jumpers that may or may not be factory-supplied. See Fig. 8 and the wiring diagrams for specific terminals to be jumpered. MOUNTING HOLES MOUNTING SCREWS (2) SUBBASE Fig. 5. Installing Q674 Subbase on wall. WIRING TERMINAL FOR STRAIGHT INSERTION– STRIP 5/16 IN. (8 MM) THERMOSTAT CABLE OPENING FOR WRAPAROUND– STRIP 7/16 IN. (11 MM) SPIRIT LEVEL BARRIER SUBBASE TERMINAL SCREW M928 Fig. 7. Barrier configuration. CAUTION POST FOR MOUNTING MOUNTING HOLES (4) THERMOSTAT (2) Equipment Damage Hazard. Never install more than one wire per terminal unless using factory-supplied jumper with spade terminal. TO SPRING FINGER CONTACTS ON THE THERMOSTAT M927 (UP TO 12) 2. 3. Fig. 6. Subbase components and leveling procedure. 4. Wire Subbase Disconnect power supply before beginning installation to prevent electrical shock or equipment damage. 60-2485—8 8 Firmly tighten each terminal screw. Fit wires as close as possible to the subbase. Push excess wire back into the hole. Plug hole with nonflammable insulation to prevent drafts from affecting the thermostat. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES JUMPER WIRE (SUPPLIED WITH SOME MODELS) 1 1 1 TWO ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY. COMPARE WIRING DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED. M5899 Fig. 8. Jumper adjacent terminals for special system hookup using stripped wire 3/4 in. (19 mm). For nonadjacent terminals and using jumper wire supplied with subbase. Table 5. Terminal Designationsa Standard Terminal Designation Alternate Designations or Customer Specials B E K Emergency heat relay G F Fan relay coil L System monitor O R Cooling damper motor; changeover valve R V Power connection to transformer (internally connected for heating and cooling) RC Power connection to cooling transformer RH Power connection to heating transformer W1 H1, R3 Stage 1 heating control W2 H2, Y, R4 Stage 2 heating control W3 Stage 3 heating controlb Y1 C1, M Stage 1 cooling control Y2 C2 Stage 2 cooling control Y3 Stage 3 cooling control X X1,X2,C T A Outdoor thermistor L, C, H HSII control panel P O A, A1, A2, Z, C, L a b Typical Connection Heating damper motor; changeover valve Clogged filter switch or common connection Defrost Momentary circuit, changeover LEDs Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic for exact connections. W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation. 9 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 5. Terminal Designationsa Standard Terminal Designation Alternate Designations or Customer Specials Typical Connection T External temperature readout, T relay R1, R2 Y a b LO and HI speed fan relays RS Cooling contactor M Compressor contactor Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic for exact connections. W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation. Outdoor Disconnect The National Electrical Code requires the installation of a disconnect switch within sight of the outdoor unit of an air conditioner or heat pump. The switch is for the safety of any technician working on the unit. The technician can assure that the unit remains unpowered. Install and Adjust Stop Brackets The stop brackets should be installed only if there is a need to restrict the adjustable range of the heating and cooling temperature setpoint levers. If adjustable lever stops are desired, order 4074ECK Envelope Assembly, which contains two adjustable lever stop brackets, one brass insert, one mounting screw and two locking screws with insulated heads. When installed, the stop brackets limit the movement of the T874 HEAT and COOL levers. TO INSTALL: 1. Remove the thermostat cover by pulling the bottom edge of the cover upward until it snaps free of the mounting slots. 2. Turn to the back of the T874 Thermostat. Locate the hole for the brass insert in the plastic base below the LED window. 3. Push the brass insert into the hole with finger. 4. Turn to the front of the T874 Thermostat. 5. Place the two stop brackets in position with the tabs in the slot between the HEAT and COOL levers. See Fig. 9. HOLES FOR INSULATED LOCKING LEVER SCREWS COOL LEVER HEAT LEVER HOLE WITH BRASS INSERT BRACKET TABS ADJUSTABLE LOCKING LEVERS ADJUSTABLE LEVER STOP BRACKETS BRACKET SLOTS NONADJUSTABLE STOPS WITH LOCKING LEVER SCREWS 75°F (24°C) MAX. HEAT 75°F (24°C) MIN. COOL MOUNTING SCREW NONADJUSTABLE D.O.D. STOPS 72°F (22°C) MAX. HEAT 78°F (26°C) MIN. COOL ADJUSTABLE STOPS M7626 Fig. 9. Range limiting and lever locking methods. 6. Insert the mounting screw into the two slots in the stop brackets and attach to the brass insert. Tighten the screw to pull the brass insert into the back of the ther- 60-2485—8 10 7. mostat. Loosen the mounting screw enough to free the stop brackets for adjustment. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 8. 9. 10. 11. Move the HEAT and COOL levers to the maximum temperature desired. Slide the stop brackets until one rests against the HEAT lever and the other against the COOL lever. Firmly tighten the mounting screw. If the HEAT and COOL levers are to be locked in place at a specific temperature, use the two insulated head screws supplied instead of the two adjustable lever stop brackets. ALLEN RETAINING SCREWS (2) CAUTION Equipment Damage Hazard. Do not use standard screws that provide metal-tometal contact with the stop brackets. Short circuit and potential equipment damage can result. M956 Mount Thermostat 1. Fig. 10. Installation of locking cover assembly. Remove the thermostat cover by pulling the bottom edge of the cover away from the base until it snaps free of the cover clip. SETTINGS NOTE: The cover is hinged at the top and must be removed by pulling up at the bottom. 2. 3. 4. 5. 6. 7. 8. Carefully remove and discard the polystyrene packing insert that protects the mercury switches during shipment. If LED indication (EM.HT., CHECK, etc.) is to be used with the Q674 Subbase, install the preprinted insert under the thermostat setpoint scale. To install, push both thermostat setpoint levers to the far ends of the thermostat. Use index finger to gently pull out the plastic setpoint scale about 1/4 in. (6 mm). Position the desired preprinted insert in the space above the LED lights. Reposition setpoint levers. Turn over the thermostat base and note the spring fingers that engage the subbase contacts. Make sure the spring fingers are not bent flat, preventing proper electrical contact with the subbase. Set the heat anticipator indicator(s) to the respective current setting of each stage. See Set The Heat Anticipator section. If the thermostat provides optional locking cover assembly, start the Allen locking screws in the cover with the wrench provided. See Fig. 10. Note the two tabs along the top inside edge of the thermostat base. The tabs fit into corresponding slots on top of the subbase. Mount the thermostat on the subbase. Align the two captive mounting screws in the thermostat base with the posts on the subbase. Tighten both screws. Do not overtighten screws or damage to subbase posts can result. CAUTION Equipment Damage Hazard. On systems using a gas valve, never apply a jumper across the valve coil terminals, even temporarily. This can burn out thermostat heat anticipator(s). Set the Heat Anticipator Move the indicator to match the primary control current draw. When using a T874 Thermostat with two stages of heating, set each heat anticipator to match its respective primary control current draw. If you cannot find the current rating on the primary control, or if further adjustment is necessary, see NOTE and use the following procedure to determine the current draw of each stage. The current draw of each heating stage must be measured with the thermostat removed and power on to the heating system. 1. 2. 3. Connect an ac ammeter of appropriate range between the heating terminals of the subbase: a. Stage 1—between W1 and RH or R; b. Stage 2—between W2 and RH or R c. Stage 3—between W3 and RH or R. Move the system switch to HEAT or AUTO. After one minute, read the ammeter and record the reading: a. Stage 1—__________A; b. Stage 2—__________A; c. Stage 3—__________A. NOTE: If equipment cycles too fast, set the indicator to a higher current rating, but not more than one-half division at a time, and recheck the cycle rate. Most conventional two-stage heating equipment is designed to operate at three cycles per hour per stage, and one-stage heating equipment at six cycles per hour, at 50 percent load conditions. When using the T874 Thermostat in heat pump systems, set the heat anticipator at 140 percent of the actual primary control current draw to reduce the cycling rate. See Fig. 11. 11 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Most heat pump systems should cycle 2-1/2 to 3 times per hour. Hang the upper edge of the thermostat cover on top of the thermostat base and swing the cover downward until it engages with the cover clip. STAGE ONE ANTICIPATOR HEATING CONTROL .1 2. 10 1.2 .8.6 .5 .4 .3 .2 .15 .12 4. .1 5 .2 .3 1.2 .8 .6 .4 STAGE TWO ANTICIPATOR HEATING CONTROL MOVE INDICATOR TO MATCH CURRENT RATING OF PRIMARY CONTROL M5069 Fig. 11. Adjustable heat anticipator scales. Temperature Setting Move the heating and cooling levers to the desired comfort positions. See Fig. 12. On some models with two stages of heating or cooling, the same lever controls both stages. The minimum differential between heating and cooling setpoints is 4°F (2°C) (5°F [3°C]) on T874W. If model has optional screws to lock temperature control levers, loosen these screws before making temperature adjustment; tighten the screws when levers are set at desired position. STAGE 1 HEATING HEATING LEVER COOLING LEVER STAGE 3 HEATING HEAT—heating system is automatically controlled by the thermostat. Cooling system is off. AUTO—thermostat automatically changes between heating and cooling system operation, depending on the indoor temperature. COOL—cooling system is automatically controlled by the thermostat. Heating system is off. EM.HT.—emergency heat relay is automatically controlled by the thermostat. Cooling system is off. Compressor is de-energized. SUPL.HT.—supplemental heat relay is energized. Cooling system is off. Compressor is de-energized. WOOD—heating system is operating with only the woodburning stage. OIL—heating system is operating with only the oil-burning stage. WOOD/OIL—wood and oil stages operate sequentially; first the WOOD stage operates, then the OIL stage operates if the WOOD stage cannot handle the load. EVAP—controls cooling system by water evaporation; see equipment instructions for further information. OVERRIDE—night setback is disabled. ON—heating system is controlled by the thermostat. EM. HT. or SUPL. HT. relay is not energized. FAN SWITCH positions control fan operation as follows: ON or CONT.—fan operates continuously. AUTO—fan operates as controlled by the thermostat in heat pump systems or conventional cooling mode; fan operates as controlled by the plenum switch in conventional heating mode. LO—fan operates constantly at low speed. MED—fan operates constantly at medium speed. HI—fan operates constantly at high speed. To move the subbase switches to the desired control positions, use thumb and index finger to slide the lever. The lever must stop over desired function indicator position for proper circuit operation. Spring return momentary position switching feature is available on selected subbase models. On these models, the fan switch is positioned to the right of the system switch. By moving the fan switch to the far right and releasing it, the ON position circuit makes. The lever springs back on release. This position is not marked on the subbase. STAGE 1 COOLING Setting the Adjustable Differential STAGE 2 HEATING STAGE 2 COOLING CAPTIVE MOUNTING SCREWS (2) The adjustable interstage differential feature, on a selected T874D model only, can be identified by the scale and tension screw near the heating and cooling mercury switches. See Fig. 13. On this model, the number of degrees between the making of the first and second stage mercury bulbs is adjustable. This feature is especially useful if the first stage controls the comfort temperature, and the second stage controls the energy savings temperature. Timers, such as the S6005, for insertion between the first and second stage control points must be ordered separately. M7625 Fig. 12. Internal view of T874W (three stages of heating, two stages of cooling). Subbase Setting The subbase switching positions control the system operation as described below. SYSTEM SWITCH (see subbase for positions): OFF—both the heating and cooling systems are off. If the fan switch is at the AUTO position, the cooling fan is also off. 60-2485—8 12 Each mark on the scale represents 1°F (0.6°C) The differential is factory set at 2°F (1°C) the differential can be set as high as 12°F (7°C) To set the adjustable interstage differential, loosen the tension screw. See Fig. 13. Slide the adjustable scale to align with the number of degrees desired between stages. Use the lower edge of the tension screw bracket as a guide for alignment. In heating, slide the lever wider apart for a larger differential, or closer together for a T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES smaller differential. In cooling, slide the lever closer together for a larger differential, or wider apart for a smaller differential. While supporting the scale with hand, tighten the tension screw. IMPORTANT Support the scale with hand while tightening tension screw. See Fig. 13. Failure to do so can result in twisting and damaging bimetal coil. HEATING SETPOINT LEVER TENSION SCREW HEAT 50 60 70 80 CAUTION Equipment Damage Hazard. When the thermostat is used to control a two-stage heating or cooling system, the second stage mercury bulb must never make before the first stage bulb, or severe equipment damage could result. To prevent this problem, provide at least 2°F (1°C) differential between stage-one and stage-two make points. Example: in heating, if stage-one makes at 70°F (21°C) stage-two should make at 68°F (20°C) or lower. Verify the Adjustment FIRST STAGE SWITCH Heating .2 1.5 Start with the heating setpoint lever all the way to the left. Slowly move the lever to the right, just until the first stage bulb makes (mercury rolls to the right side of the bulb). Note the setting on the temperature scale. Slowly move the lever to the right until the second stage bulb makes. Note the setting on the temperature scale. The difference between the two temperatures is the interstage differential, which should match the number set on the scale with the tension screw. 1.2 .8 .6 .4 SCALE .3 SECOND STAGE (ADJUSTABLE) SWITCH HEATING Cooling Start with the cooling setpoint lever all the way to the right. Slowly move the lever to the left, just until the first stage bulb makes (mercury rolls to the left side of the bulb). Note the setting on the temperature scale. Slowly move the lever to the left until the second stage bulb makes. Note the setting on the temperature scale. The difference between the two temperatures is the interstage differential, which should match the number set on the scale with the tension screw. TENSION SCREW ALIGN LOWER EDGE WITH SCALE NOTCH 10°F SCALE SLIDE LEVER WIDER APART FOR LARGER DIFFERENTIAL CHECKOUT 1 Heating COOLING Move the system switch on the Q674 Subbase to HEAT or AUTO. Move the heat lever on the T874 about 10°F (6°C) above room temperature. See Fig. 12. Heating system should start and the fan should run after a short delay. Move the heat lever about 10°F (6°C) below room temperature. The heating equipment should shut off, and the fan should run for a short time, then shut off. TENSION SCREW ALIGN LOWER EDGE WITH SCALE NOTCH 4°F SCALE SLIDE LEVER CLOSER TOGETHER FOR LARGER DIFFERENTIAL In heat pump applications, sometimes time delays are involved before the compressor and auxiliary heat are activated. This is due to a minimum-off timer, which prevents the compressor from restarting for five minutes from when the thermostat last turned off the compressor, or from when the system first received power. 1 1 EACH MARK ON THE SCALE REPRESENTS 1°F (0.6°C). M937 Fig. 13. Set adjustable interstage differential. Cooling CAUTION Equipment Damage Hazard. Do not operate cooling if outdoor temperature is below 50°F (10°C). Refer to manufacturer recommendations. 13 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Thermometer Move the system switch on the Q674 Subbase to COOL or AUTO. Move the cool setting lever on the T874 Multistage Thermostat about 10°F (6°C) below room temperature. See Fig. 12. The cooling equipment and fan should start. If the system has two stages of cooling, both stages should start. Move the cool lever about 10°F (6°C) above room temperature. The cooling equipment and fan should stop. The thermometer in your thermostat has been accurately calibrated at the factory. The thermometer should only need adjustment if it has been dropped or shifted due to mishandling. Fan Move the system switch to COOL, OFF, or AUTO. If necessary, position both temperature setting levers so that the heating and cooling equipment are off. Move the fan switch to ON or CONT. The fan should run continuously. When the fan switch is in AUTO, LO, MED, or HI position, fan operation is controlled by the heating or cooling system. Outdoor Reset Thermistor (Where Applicable) If the system is supplied with a thermistor, it must be used; if not used, thermostat performance deviates radically from proper operation. If the setpoint lever and the thermometer reading do not agree, use the following procedure: 1. Remove the thermostat cover by pulling up from the bottom edge of the cover away from the base until it snaps free of the cover clip. 2. Set the thermostat cover on a table near an accurate thermometer. 3. Allow ten minutes for cover thermometer to sense area temperature; compare the readings. Be careful not to touch thermometer or breathe on it. 4. If the readings are the same, replace cover and put the system into operation. 5. If the readings are different, insert a small screwdriver in the thermometer slot and turn it until the thermometers have the same reading. See Fig. 15. 6. Replace thermostat cover and put the system into operation. THERMISTOR RESISTANCE (ohms) The proper thermistor operation must be verified to ensure the correct operation of the thermostat. Check thermistor operations as follows: 1. Disconnect the T wire on the subbase. 2. Use an ohmmeter to measure resistance between the T wire and the A subbase terminal. 3. Take outdoor temperature at thermistor location and find the correct thermistor resistance on the Fig. 14 chart. 4. If the resistance measured in step 2 and the calculated resistance in step 3 vary by more than 15 percent, the thermistor requires replacement. Contact Honeywell or installing dealer for replacement packaged outdoor thermistor, part no. C815A1005. 4600 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0 C815A THERMISTOR RESISTANCE R = 400 ohms ± 10% AT 77°F (25°C) M5070 Fig. 15. Thermometer calibration. UNDERSTANDING CIRCUITS To understand wiring diagrams, it is important to know what all the symbols mean and how to trace the path of the circuits from the transformer. See Fig. 16 through 25. -20 0 20 40 60 80 100 120 TEMPERATURE OF THERMISTOR (°F) Circuit descriptions and terminology are defined as follows: For standard heating-cooling circuits: Auto changeover—refers to the presence of an AUTO position in the system switching (EX: Q674E with OFFHEAT-AUTO-COOL switching). The thermostat automatically changes between heat and cool modes as indoor temperature changes. Manual changeover—requires a system switch movement to change mode (EX: Q674B with HEAT-OFF-COOL switching). T874D Multistage Thermostats with 2 heat or 2 cool switches are shown on most standard circuits. Most standard or TRADELINE® subbases (Q674A-E,G) can be used with T874A-F standard or TRADELINE 140 M1590A Fig. 14. Thermistor resistance chart. CALIBRATION Thermostat T874 Thermostats are accurately calibrated at the factory. They do not have provision for field calibration. 60-2485—8 14 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES thermostats. The schematics can be field-modified as required (EX: if T874C is being used, eliminate second stage of heat). For heat pump circuits: Cool changeover valve—operates on cooling. The reversing valve or relay is activated either by moving the system switch to COOL (manual changeover) or by a mercury switch that makes on a temperature rise (auto changeover). Heat changeover valve—operates on heating. The reversing valve or relay is activated either by moving the system switch to HEAT (manual changeover) or by a mercury switch that makes on a temperature fall (auto changeover). System monitor relay—optional equipment on some heat pumps includes an R4222P1065 or equivalent. This system monitor relay detects a malfunction in the compressor and indicates the malfunction by activating the EMERGENCY HEAT LED on the Q674 Switching Subbase. The system monitor relay is usually wired into the L terminal on the Q674. Each mercury switch is identified by function: H1—Stage 1 Heating. H2—Stage 2 Heating. H3—Stage 3 Heating. C1—Stage 1 Cooling. C2—Stage 2 Cooling. C3—Stage 3 Cooling. C/O—Changeover (heat pumps). 5. perature rise. Fixed anticipation is represented by a zigzag line and adjustable anticipation is a zigzag with an arrow. The resistance of the fixed anticipator is so large it limits current so that a system relay cannot be pulled in from a circuit path going through the fixed anticipator. The relay can be pulled in through an adjustable anticipator because its resistance is generally 0 to 5 ohms. The center portion (the subbase) contains the switches. The fan switch is above the system switch. The small circles on the switch represent the maximum possible contacts available on the Q674 Subbase. The larger circles represent the switch positions available on this particular Q674, with the solid circle representing where it is actually switched on the diagram. NOTE: Solid circles are not interconnected electrically. At the right, the relays and contactors are shown, attached to the proper terminals. The terminals are represented by large circles with terminal designations in capital letters. See Table 3 for the meaning of each lettered terminal. Sometimes power for a fixed anticipator is brought through an off system relay like the changeover relay shown in Fig. 20. This current is kept low by the high resistance of the fixed anticipator so that relay does not pull in. KEY TO HOOKUP SYMBOLS Each anticipator is identified and each switch affected is named (EX: H1 anticipator, C1 anticipator). All T874 Multistage Thermostats use mercury switches. Each schematic indicates switch operation by being drawn in the open position with an arrow indicating operation with a temperature RISE or FALL. TRANSFORMER (24 VAC SECONDARY) RELAY/CONTACTOR CONTACTS B TERMINAL RELAY OR CONTACTOR COIL One circuit has been selected that is typical of various models used with heat pumps. This circuit has been traced to illustrate the functions performed by these control systems. LED MERCURY SWITCH Tracing Method: 1. 2. 3. 4. ODT OUTDOOR THERMOSTAT EHR EMERGENCY HEAT RELAY Always begin at the system transformer or R terminal. You may want to draw the switch contacts in each switch position to aid in tracing. Colored pencils are helpful when only one copy of the circuit is available. See Fig. 16 for a description of the hookup symbols and Fig. 17 through 25 for typical hookups. Completely trace only one circuit at a time (for example: heat or cool). Connections are indicated by small dots at the point of intersection. If there is no dot, there is no connection. The left portion of the circuit (the thermostat) contains the mercury switches. The heat switches make on a temperature fall, and the cool switches make on a tem- 15 FIXED ANTICIPATOR HIGH RESISTANCE (TYPICALLY 5 KILOHMS) RTD TIME DELAY RELAY RD DEFROST RELAY ADJUSTABLE ANTICIPATOR LOW RESISTANCE (TYPICALLY 0 TO 5 OHMS) CHP PRESSURE SWITCH LACO LOW AMBIENT CUTOFF M5848 Fig. 16. Key to hookup symbols. 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS (HOT) L1 L2 1 H1/C1 ANTICIPATOR R 2 FALL ODT 1 H1 RTD 1 C1 EHR 1 RTD 2 W3 3 4 FAN SWITCH ODT 2 AUTO EHR 2 ON H2 ANTICIPATOR W2 5 H2 RTD 3 RTD 1 AUX. HT. LED (GREEN) 6 2 FALL X EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT OFF COOL CHANGEOVER VALVE E COOL EM. HT. RELAY CHP LACO Y B 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 AUXILIARY HEAT LED AVAILABLE ON SOME MODELS. COMPRESSOR CONTACTOR M5072A Fig. 17. Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application. The thermostat provides two-stage heating and one-stage cooling manual changeover operates on cooling. 60-2485—8 16 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT L1 (HOT) R H1/C1 ANTICIPATOR FALL SYSTEM COMPONENTS ODT 1 L2 2 1 RTD 1 FAN SWITCH H1 C1 EHR 1 RTD 2 W3 3 AUTO 4 ODT 2 ON EHR 2 W2 H2 ANTICIPATOR 5 6 X EM. HT. LED (RED) H2 FALL SYSTEM SWITCH RTD 3 RTD 1 AUX. HT. LED (GREEN) SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT OFF EM. HT. RELAY CHANGEOVER VALVE E COOL 1 CHP LACO POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y COMPRESSOR CONTACTOR B M5840 Fig. 18. Tracing the changeover relay circuit. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1/ C1 ANTICIPATOR FALL L1 (HOT) R ODT 1 2 RTD 1 H1 FAN SWITCH C1 EHR 1 AUTO ODT 2 ON AUX. HT. LED (GREEN) 5 FALL EHR 2 W2 H2 ANTICIPATOR H2 X 6 EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD FAN RELAY G EM. HT. O HEAT OFF POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. RTD 3 RTD 1 L 1 RTD 2 W3 3 4 L2 1 CHANGEOVER VALVE E COOL EM. HT. RELAY CHP LACO Y B COMPRESSOR CONTACTOR M5841 Fig. 19. Tracing the heat 1 and anticipation circuit. 17 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1/ C1 ANTICIPATOR FALL L1 (HOT) R 2 ODT 1 L2 1 H1 C1 3 RTD 1 FAN SWITCH EHR 1 RTD 2 W3 4 AUTO ODT 2 ON H2 ANTICIPATOR AUX. HT. LED (GREEN) 6 H2 EHR 2 W2 5 RTD 3 RTD 1 X FALL EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. EM. HT. RELAY CHANGEOVER VALVE E COOL CHP LACO Y COMPRESSOR CONTACTOR B M5842 Fig. 20. Tracing the heat 1 anticipation circuit. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1/C1 ANTICIPATOR L1 (HOT) R ODT 1 RTD 1 H1 L2 2 FALL FAN SWITCH C1 EHR 1 1 RTD 2 W3 3 AUTO 4 ODT 2 ON AUX. HT. LED (GREEN) 5 H2 EHR 2 W2 H2 ANTICIPATOR X 6 FALL EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CHANGEOVER VALVE E EM. HT. RELAY COOL CHP LACO Y B COMPRESSOR CONTACTOR Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit. 60-2485—8 RTD 3 RTD 1 18 M5843 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) R H1/C1 ANTICIPATOR ODT 1 1 RTD 1 FAN SWITCH H1 L2 2 FALL C1 EHR 1 RTD 2 W3 3 AUTO 4 ODT 2 ON AUX. HT. LED (GREEN) 5 FALL RTD 3 RTD 1 X 6 H2 EHR 2 W2 H2 ANTICIPATOR EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT OFF 1 EM. HT. RELAY CHANGEOVER VALVE E COOL POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CHP LACO Y COMPRESSOR CONTACTOR B M5844 Fig. 22. Tracing the emergency heat and EM. HT. LED circuit. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) R H1/C1 ANTICIPATOR ODT 1 2 FALL RTD 1 H1 FAN SWITCH C1 L2 1 EHR 1 RTD 2 W3 3 AUTO 4 ODT 2 ON AUX. HT. LED (GREEN) 5 H2 EHR 2 W2 H2 ANTICIPATOR X 6 FALL EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L O HEAT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FAN RELAY G EM. HT. 1 RTD 3 RTD 1 OFF CHANGEOVER VALVE E COOL EM. HT. RELAY CHP LACO Y B COMPRESSOR CONTACTOR M5845 Fig. 23. Tracing the cooling circuit. 19 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) R H1/C1 ANTICIPATOR ODT 1 FALL 1 RTD 1 FAN SWITCH H1 L2 2 C1 EHR 1 RTD 2 W3 3 AUTO 4 ODT 2 ON AUX. HT. LED (GREEN) 5 FALL RTD 3 RTD 1 X 6 H2 EHR 2 W2 H2 ANTICIPATOR EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. OFF EM. HT. RELAY CHANGEOVER VALVE E COOL CHP LACO Y COMPRESSOR CONTACTOR B M5846 Fig. 24. Tracing the auto fan circuit. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) R H1/C1 ANTICIPATOR ODT 1 2 FALL RTD 1 H1 FAN SWITCH C1 EHR 1 ODT 2 AUTO ON AUX. HT. LED (GREEN) 5 FALL EHR 2 W2 H2 ANTICIPATOR H2 RTD 2 W3 3 4 L2 1 RTD 3 RTD 1 X 6 EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT E OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL EM. HT. RELAY CHP LACO Y B Fig. 25. Tracing the fan on circuit. 60-2485—8 CHANGEOVER VALVE 20 COMPRESSOR CONTACTOR M5847 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES OPERATION Heat anticipators add heat during the call for heat. Cooling anticipators are activated while the air conditioner is off. See Fig. 28. This heater makes the thermostat think it is warmer than it really is, and brings it on sooner than the bimetal alone would. Heat Anticipation/Cool Anticipation When controlling a heating unit with a thermostat, the temperature does not remain exactly at the thermostat setpoint, but varies within a certain temperature range. Heat anticipation is added to the thermostat to reduce this range. L1 L2 (HOT) The anticipator is a small resistive heater in the thermostat that heats when the system is on (heat mode) or off (cool mode). The heat produced by the anticipator raises the internal bimetal temperature slightly faster than the surrounding room temperature. The thermostat anticipates the need to shut off the heating system sooner than it would if affected by room temperature only. RISE C1 C1 ANTICIPATOR There are two types of heat anticipation, adjustable and fixed. Adjustable anticipation is also called current anticipation. See Fig. 26. The heater is in series with the mercury switch and heating primary. The pointer is adjusted to match the current draw of the primary control, and the correct amount of heat is added for proper cycle rates. L1 L2 (HOT) H1 STAGE 1 HEAT RELAY M5823 Fig. 26. Adjustable anticipation heater in series with load. Fixed anticipation is also called voltage anticipation. See Fig. 27. The heater is in parallel with the primary control and is not affected by the current draw of the primary. It establishes the proper cycle rate for any application. Fig. 28. Internal cooling anticipation schematic. Interstage Differential The mercury switch of each stage of heat makes at a slightly different temperature; that is, the mercury makes the contacts of the first stage bulb at one temperature, and the second stage bulb at another temperature. The difference between these two temperatures is the interstage differential. Mechanical differential is the difference between the make and break points of each switch. The mechanical differential for the T874 is 1°F (0.6°C) between the stages of heating or between the stages of cooling for most models. Droop The addition of anticipator heat to the bimetal causes a control factor called droop. As the weather grows colder, the heating appliance must operate longer and more frequently. More heat must be added to the bimetal. The bimetal now thinks it is warmer than it really is, and actual room temperature is controlled at a lower temperature than the setpoint indicates. At 100 percent heat load, this droop can be significant. L1 L2 (HOT) The C815A Outdoor Reset Thermistor is used in heat pump systems to minimize droop. Without some method of countering this situation, the occupant could notice the temperature offset. STAGE 1 HEAT RELAY FALL H1 M5825 Interstage differential is the difference between the two make points when the bulbs are controlled by the heating of the bimetal and the action of the heat anticipator. The interstage differential is 1.9°F (1°C) between the stages of heating or the stages of cooling for most models. H1 ANTICIPATOR FALL STAGE 1 COOL RELAY H1 ANTICIPATOR Outdoor Reset M5824 Some T874/Q674 models are intended for use with the C815A Outdoor Thermistor. The outdoor thermistor provides significantly improved thermostat performance when compared to conventional multistage thermostats. The C815A is usually located in the heat pump condensing unit outdoors. Fig. 27. Fixed anticipation heater in parallel with load. 21 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES CAUTION Equipment Damage Hazard. Due to calibration techniques used for T874 Thermostats with outdoor reset, the C815A Thermistor must be wired into the system at all times. Failure to do so will result in serious degradation of performance. Service and Replacement of C815A Outdoor Thermistor THERMISTOR RESISTANCE (ohms) To check and verify thermistor operation, perform the following steps: 1. Disconnect wire from T terminal on subbase. 2. Measure resistance with ohmmeter across the T subbase wire and X subbase terminal. 3. Take outdoor temperature measurement at thermistor location and find correct thermistor resistance on the chart in Fig. 29. 4. Compare resistance on the chart with measured resistance. Replace C815A if resistance varies more than 15 percent. Contact installing dealer for packaged replacement outdoor thermistor. LEDs cannot be replaced or added in the field. LEDS 80 4600 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 0 EM. HEAT FILTER SERV. AUX HEAT 50 60 70 80 COOL C815A THERMISTOR RESISTANCE R = 400 ohms ± 10% AT 77°F (25°C) M5830 Fig. 30. T874/Q674 LED location. Restricted Setpoint (DoD) The Department of Defense (DoD) models are equipped with a restricted setpoint feature for fuel efficiency. -20 0 20 40 60 80 100 120 TEMPERATURE OF THERMISTOR (°F) Fixed stops are factory-set so setpoint levers cannot be set above 72°F (22°C) on heating, or below 78°F (26°C) on cooling. 140 M1590A Applications Fig. 29. Thermistor resistance chart. Features Two of the features of the T874/Q674 include LED indicators and restricted setpoint. LED Indicators The light-emitting diodes (LED) indicators on the subbase light on command when something specific happens in the system. See Fig. 30. The T874/Q674 can be applied to standard residential systems for automatic or manual changeover, to commercial rooftop applications, or to heat pump applications. Changeover on Standard Residential Systems In a standard residential heating-cooling circuit, changeover between heating and cooling can be done either automatically or manually. Up to four different LEDs are available. The thermostat has a clear lens window for viewing each LED. On TRADELINE models, a small insert is used so the LED function desired can be selected. This must be done during installation. A blank insert is factory-installed in some T874 models. To remove it, push both temperature setting levers to the far ends of the thermostat. Use index fingernail to gently pull out the scaleplate a fraction of an inch. Turn thermostat upside-down, and the blank insert falls out. 60-2485—8 A strip of four inserts is included with TRADELINE T874. Drop a strip into the recessed area behind the scaleplate so selected LEDs show. Make sure insert is completely seated in recessed area. Let scaleplate pop back; then set levers to desired position. • FILTER LED lights when the filter is clogged and needs replacement. • CHECK LED lights when something needs to be checked or done to maintain efficient operation of system. See heating system instructions for CHECK LED meaning. • EM. HT. LED lights when the emergency heat is operating. • SUPL. HT. LED lights when the supplemental heat is operating. • LOCKOUT LED lights when the system is shut down and needs maintenance. • AUXILIARY HEAT LED lights when the auxiliary heat is operating. • SERVICE or MALFUNCTION LED can have several meanings. Consult heating system instructions. 22 Automatic changeover is done by an AUTO position on the subbase system switch. See Fig. 31. When the switch is in the AUTO position, the thermostat automatically changes between heat and cool modes, depending on the indoor temperature. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES When enthalpy is low enough, the thermostat and a sensor tell the economizer damper to open to let in cool air from the outside. When enthalpy is high, the thermostat and sensor tell the damper to close. No more outside air comes in, so the air conditioner is used instead. Heat Pump Application OFF EM. HT. HEAT AUTO COOL M5828 Fig. 31. System switching for automatic changeover. Automatic changeover is frequently used in areas where there are large temperature differences in 24 hours. Some uses for the automatic changeover feature are in the southern states (cool in the morning and hot in the afternoon) and in commercial applications. Manual changeover requires a system switch movement to change the mode. See Fig. 32. Most manual changeover switches consist of HEAT-OFF-COOL choices. For heating, switch to HEAT. For cooling, switch to COOL. It is not automatic. Manual changeover is often used in areas where the temperature is relatively stable between day and night. A heat pump system operates much like an air conditioner. However, the heat pump is capable of moving heat in two directions; from inside the home to outdoors for cooling, or from outdoors to inside for heating. The heat pump can be controlled by separate relay/contactor components, which are energized or de-energized by the T874. Changeover between heating and cooling for heat pump circuits can be accomplished either manually or automatically. Manual changeover control requires a system switch movement to change the mode. The reversing valve is activated by moving the system switch to COOL for cooling or to HEAT for heating operation. Automatic changeover is accomplished by one of the mercury bulb switches in the thermostat. On a system with automatic changeover on cooling, the changeover valve is energized by a mercury switch that makes on a temperature rise. On heating, the changeover valve is energized by a mercury switch that makes on a temperature fall. A description of the methods used to control heat pumps follows. OFF EM. HT. HEAT COOL M5829 Space Temperature Sensing Low Voltage Controls Fig. 32. System switching for manual changeover. Commercial Rooftop Application The T874 can be used as part of a commercial rooftop application to run mechanical cooling. An economizer is often used as part of a rooftop application to save on air conditioning. See Fig. 33. Control systems for heat pumps usually utilize low voltage control circuits. The variety of control functions required and the relative complexity require a versatile and economical method of control. There are several interlocks and indication functions that would be more difficult and expensive to wire in line voltage circuits. Low voltage controls have the precision and flexibility needed. The thermostat used is a low voltage device that has good temperature sensitivity and several manual and automatic switching capabilities. OUTDOOR AIR Two-Stage Thermostat H205 OR H705 ENTHALPY CONTROL RETURN AIR In most installations, the heat pump itself requires auxiliary heat, usually in the form of electric strip heaters, to carry the building heating load at design conditions. Since the heat pump is usually more efficient, the control strategy is to run the heat pump whenever possible and the auxiliary heat only when necessary—during very cold weather or if the heat pump fails. Usually the auxiliary heat is used only below the balance point (temperature at which the heat pump cannot handle heating load by itself). DISCHARGE AIR SENSOR DOWNSTREAM FROM THE EVAPORATOR COIL M5827A Fig. 33. Typical commercial rooftop economizer application. A two-stage thermostat makes this possible. The two stages make sequentially as the temperature drops. There is a degree or two between stages so that the second stage (the Enthalpy is the temperature and humidity of the air. A more accurate analysis of the suitability for free cooling can be made by monitoring the enthalpy. 23 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES one controlling the auxiliary heat) makes only when the heat pump alone cannot handle the load. That is how the strategy of using the most economical heat first is implemented. Cycling Rate Normally, thermostat anticipation is set to cycle a fossil fuel furnace about five or six times an hour (at 50 percent load). This provides a reasonable balance between comfort, stability and economy. A heat pump, being a mechanical refrigeration system, should be cycled at a rate of 2-1/2 to 3 times an hour. With a T874, this is accomplished by setting the anticipator at the total current draw of the controlled device (the contactor and possibly the changeover relay or valve). Most likely, the compressor operates from the first stage of the thermostat. The second stage normally controls the auxiliary heaters. This heat anticipator can be set for the current draw of the electric heat primary, and produces good control. This is particularly important on the 3-stage T874. The additional stage means that more droop is introduced when the system is in operation. That is the reason the TRADELINE T874W is sold in a package with the outdoor sensor and the correct subbase. Outdoor Reset—How it Works The heater in the thermostat is connected in series with a thermistor sensor that measures outdoor temperature. See Fig. 34. In warm weather, the thermistor has very low resistance, permitting a large current flow in the heater, which generates a relatively large amount of heat in the thermostat. In cold weather, the outdoor sensor has high resistance, which results in low current flow and little or no heat being added to the thermostat. This raises the control point, overcoming the effects of droop and interstage differential. L1 L2 (HOT) Voltage Anticipation Although not a specific requirement for heat pumps, several models of the T874 have voltage heat anticipation instead of current anticipation. With voltage anticipation, the amount of heat added to the thermostat is constant no matter which load is connected to it. The anticipator realizes a constant voltage and produces a constant amount of heat during the ON cycle. This allows the cycling rate to be designed into the thermostat. The heat pump manufacturer is assured of correct performance independent of later thermostat adjustments. C815A OUTDOOR THERMISTOR SENSOR M5826 Fig. 34. Location of thermistor. Changeover Outdoor Reset Outdoor reset, which a C815A Outdoor Thermistor makes possible, is sometimes applied in heat pump systems to help minimize the effect of the differential between stages. It takes 2°F (1.1°C) change in temperature to bring on the second stage and full heating. Added to a certain amount of droop under high loads, there can be a large offset between the setpoint and room temperature. Without some method to counteract this situation, the temperature offset from the setpoint could be as much as 6°F (3.3°C) under high load conditions. It is not likely that the occupants accept this variation without making frequent thermostat setting changes. Outdoor reset has the effect of raising the setpoint at cold outdoor temperatures. Then, even with a few degrees droop, the space temperature stays near the desired setting. This is done by calibrating the thermostat high by 5°F (3°C)— the amount of expected offset. This offset compensates for differential and droop at high load factors so the thermostat switches at the setpoint. At warm temperatures, heat is added to the thermostat to compensate for this offset; at cold temperatures, the extra heat is automatically removed. The effect is the same as raising the setpoint as the outdoor temperature goes down. 60-2485—8 RESET HEATER 24 Changeover between heating and cooing can be accomplished either automatically or manually, depending on the application. Changeover can occur in heating or cooling. The changeover valve is energized as long as the subbase function switch is in the appropriate position when manual changeover is used. If a system manually changes over on cooling, the valve energizes whenever the subbase switch is in the cooling mode. One of the mercury bulb switches is used for control when the thermostat has automatic changeover. When the automatic changeover is in cooling, the changeover valve is energized when the first stage cooling switch makes. The second stage switch turns on the compressor. It is more common with new equipment to find that changeover occurs with cooling; that is, the changeover valve is energized to produce cooling. Whether automatic or manual changeover is used and whether the reversing valve is energized with cooling or with heating, a heat pump system can be controlled by the appropriate T874 Multistage Thermostat. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Low Temperature Lockouts Some manufacturers of heat pumps have previously controlled their units so the compressor was locked out below a specified outdoor temperature. This was done because of the stress placed on the compressor by the very cold temperatures, and the fact that efficiency drops off at low temperatures. Other manufacturers say that although efficiency is low at cold temperatures, the problem of starting the cold compressor is the most critical point. It is more important to keep the compressor running than to shut it off and try to restart it when the temperature warms up to +10°F (-12°C). Also the crankcase heater, which can run only when the compressor is off, compensates for the lower compressor efficiency. So, it is equitable to let the heat pump run even with a coefficient of performance (COP) slightly less than one, rather than to turn it off and have to run the crankcase heater. NOTE: To determine the COP of a heat pump, use the following formula: COP = Btu Out/Btu we pay for or Btuh Capacity Unit Wattage x 3.413 Btu/Watt Another factor favoring this control strategy is that newer heat pump designs maintain a level of efficiency even at outdoor temperatures well below zero. Some brands do not reach 1.0 COP until -25°F (-32°C). Virtually all manufacturers now let the heat pump run continuously rather than lock it out at cold temperatures. THERMOSTAT HEAT 2 HEAT 1 COMP. STAGE 1 COMP. STAGE 2 OUTDOOR THERMOSTAT AUXILIARY HEAT M5838 Fig. 35. Two-stage heat pump with two-stage thermostat. The outdoor thermostat is set at the balance point with both heat pump stages running. So if the heat pump can control the heating load down to +20°F (-7°C), the auxiliary heat comes on with the second stage of the compressor. In effect, this control strategy changes the heat input of the second stage, depending on the amount of heat needed. Additional stages of auxiliary heat can be added with or without the control of more outdoor thermostats, See Auxiliary Heat section. Another way to control a two stage heat pump is with a threestage thermostat. The T874W is designed for this application as well as others. See Fig. 36. Heat Pumps with Dual Compressors Staging residential sized heat pumps is a requirement that developed from the need to make heat pumps as efficient as possible. One of the methods used to improve overall seasonal efficiency is to reduce the amount of time the machine is operating in a transitional mode. Transitional mode is starting and stopping in addition to recovering from defrost. Under light loads, when the heat pump is cycling on and off, this can be a significant amount of time and can result in a significant efficiency reduction. Capacity control is one way to reduce the cycling rate and improve the efficiency. The advantage of this system is that no auxiliary heat is used until there is an actual demand from the controlled space. THERMOSTAT HEAT 3 HEAT 2 HEAT 1 COMP. STAGE 1 COMP. STAGE 2 Additional capacity control methods used on other refrigeration systems (unloading, multiple compressors) are not as likely to be seen on residential heat pumps. With a single-stage heat pump, the compressor is normally controlled by the first stage and the auxiliary heat by the second stage. The T874G, N and R Thermostats are used for this purpose. With a two-stage compressor, the two thermostat switches control the individual compressor stages. Auxiliary heat is controlled along with the compressor stage-two, by the thermostat second stage. It comes on with the compressor high speed if an outdoor thermostat—wired in series with it— is made. See Fig. 35. AUXILIARY HEAT M5837 Fig. 36. Two-stage heat pump with three-stage thermostat. Two speed Heat Pump One way to control capacity is to use a two-speed compressor. The compressor runs at low speed for stage-one heating and cooling. The compressor runs at the low speed instead of cycling the heat pump on and off under some light load conditions. The high speed is stage-two cooling. The compressor runs on high speed when loads increase so the low speed can no longer handle the cooling load. This reduces cycling rate and improves capacity. 25 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Defrost Control In some regions, during half or more of the heating season, the outdoor coil operates below 32°F (0°C) Frost or ice builds up on the outdoor coil of a heat pump similarly to the frost buildup in a household refrigerator. Eventually, this accumulation of ice interferes with efficient heat transfer from the outdoor air to the coil and refrigerant. Defrosting is occasionally required to remove this ice, and restore the heat pump ability to absorb heat from the air. L1 L2 (HOT) TRANSFORMER THERMOSTAT HEAT 2 HEAT 1 Defrosting A heat pump defrosts its outdoor coil by temporarily switching to the cooling mode, which causes hot gas from the compressor to be directed to the outdoor coil instead of to the indoor coil so the heat pump is taking heat from the home to warm up the outdoor coil. Defrosting is the greatest detriment to heat pump efficiency. Defrost Control Functions Besides changing over to the cooling mode, defrosting requires several more control initiated actions that follow. OUTDOOR FAN When defrosting has begun, it is standard practice to turn off the outdoor fan to speed up the melting process. A separate defrost relay is required to control that fan. See Fig. 37. Other contacts can be needed on the defrost relay to power the changeover valve or power part of the auxiliary heat. CONTACTOR COMPRESSOR MOTOR DEFROST RELAY CONTACT AUXILIARY HEAT RELAY M5835 Fig. 38. Auxiliary heat with defrost control. WHEN TO DEFROST Timely defrosting is an essential component of effective heat pump operation. Failure to defrost often enough permits too much ice to accumulate on the coil. At the very least, this hurts efficiency; at worst, it results in compressor damage. Insufficient defrosting is a condition the heat pump manufacturer wants very much to avoid. A 50 percent reduction in outdoor airflow is the maximum that would be tolerated. So the designer of a heat pump would select a control point that puts the system into defrost when airflow through the outdoor coil approaches half its normal level. Restricted airflow causes a greater load on the compressor; the outdoor coil runs colder, suction pressure is lower and the motor runs hotter. At the other end of the scale, defrosting too often hurts the overall energy efficiency of the system. Consider that in terms of heating the building, defrosting is a big loss. Not only does the system stop heating, but it actually moves heat out of the building. If electric strip heat is used, it is a further waste because its COP is 1.0 and not the 2.0 or more COP realized if the heat is provided by the heat pump. CONTROLLED BY OUTDOOR DEFROST RELAY FAN MOTOR So, concern for equipment safety suggests fairly frequent defrosting while economy of operation argues for fewer defrost cycles. Since the equipment manufacturer chooses, the balance is usually tipped in favor of more frequent defrosting to avoid the possibility of damaging the compressor. M5839 Fig. 37. Outdoor fan with defrost control. AUXILIARY HEAT DURING DEFROST Most pump manufacturers bring on some auxiliary heat during defrost, although this is not a universal practice. Some rely on the second stage of the thermostat to call for auxiliary heat as needed. Since the heat pump is operating in the cooling mode to defrost, it is delivering cold air to the living space. Auxiliary heat is used to offset this cooling. It requires another normally open contact on the defrost relay. See Fig. 38. Auxiliary Heat Except in warm climates, all air-to-air heat pump installations require auxiliary heat capability. Electric resistance heaters can provide this auxiliary heat. The electric heaters (sometimes called strip heaters) usually are supplied in 5 kW units or strips (about 17,000 Btu). The indoor unit of the heat pump is designed to accommodate various electric heat units so it can be used in variously sized buildings in different parts of the country. Two-Stage Thermostat The most common heat pump control strategy is for the thermostat first stage to switch the compressor and the second stage to switch the auxiliary heat. See Fig. 39. 60-2485—8 26 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES The disadvantage of this system is that it can require several outdoor thermostats. Also, since the unit is operating most often at nearly full capacity, the thermostat is on longer which results in more droop, with a little more offset from the thermostat setpoint. THERMOSTAT HEAT 2 HEAT 1 COMPRESSOR CONTRACTOR CONTROLS AT 65°F (18°C) AUXILIARY HEAT RELAY CONTROLS AT 63°F (17°C) In addition, the capacity is tied to theoretical load, based on heat loss calculations. Normally this is very close to the actual load, but there are times where the second stage is switched on too soon (no harm done) or too late (the building gets cold). M5836 Fig. 39. Auxiliary heat in two-stage thermostat. This method keeps the auxiliary heat off until the heating load is large enough to demand 100 percent heat pump operation. That demand is measured by the thermostat and is the actual heat requirement of the space. The two-stage thermostat requires about a 2°F (1.1°C) room temperature drop to bring on the second stage. Stage or Time Modulated Control There are two different ways to control auxiliary heat, staged or time modulated control. Outdoor thermostats are used to switch additional increments of electric heat into the thermostat circuit as the outdoor temperature gets lower. All increments of auxiliary heat are still controlled by stage-two of the thermostat but only if the outdoor temperature requires the additional capacity. See Fig. 40. The T874 Thermostat produces time modulated control, which is the on time of the thermostat changing during each cycle as the load changes. The on time of the heating system is directly proportional to the heating load of the building. As an example of the quality of time modulated control, consider the typical gas furnace. It can have a capacity of 100,000 Btu (293 kW), which is controlled On-Off. The output is 100,000 Btu (293 kW) or nothing. A quality thermostat controls so closely that the occupants rarely detect changes in room temperature. The same is true with 50,000 or 60,000 Btu (146.5 or 178.8 kW) of heat pump auxiliary electric heat. The T874 can provide the same high quality control. This scheme also eliminates the need for outdoor thermostats and thus offers the manufacturer an opportunity to reduce unit cost. One disadvantage is that a thermostat jiggler can be demanding more kW of strip heat when chilly. The method any particular manufacturer selects depends on which arguments it finds persuasive and the opinions of its distributors and dealers. Three-Stage Thermostat A definite improvement in quality of control and economy can be achieved with a three-stage thermostat (T874W), which is especially true with heat pumps using dual compressors. THERMOSTAT HEAT 2 HEAT 1 Three-stage control permits both the heat pump and the auxiliary heat to be tied directly to the demand of the controlled space. With a two-stage compressor, maximum (100 percent) heat pump operation is required before auxiliary heat is brought on. COMPRESSOR CONTACTOR AUXILIARY HEAT RELAY 1 20°F (-7°C) OUTDOOR THERMOSTATS Emergency Heat AUXILIARY HEAT RELAY 2 Some provision is generally required to back up the compressor in the event of a failure during the heating season. In fact, it is quite common to find that local building codes or electric utilities require that a specified percent of the building heating requirements be available from emergency heat—a source other than the heat pump compressor. Almost universally, the source is electric resistance heaters. Typically, the requirement is for 70 or 80 percent of the building heating needs. 5°F (-15°C) AUXILIARY HEAT RELAY 3 M5834 Fig. 40. Outdoor thermostats for auxiliary heat. The rationale for this system is that it very closely matches the system capacity to the heating load of the building. By calculating the heat loss of a building, the installing contractor can pick the theoretical outdoor temperature at which to permit each additional unit of electric heat to be operated by the second stage of the room thermostat. Switching to Emergency Heat Conventional heat pump control (thermostat logic) usually includes a manual subbase switch to bring on the emergency heat. In one control strategy, the emergency heat relay is turned on by the EM.HT. selector switch on the thermostat subbase. The compressor is prevented from running. The electric heaters are cycled as they normally would be by the second stage of 27 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES the thermostat. A set of contacts on the emergency heat relay is used to bypass each outdoor thermostat so that all electric heat is under immediate thermostat stage-two control. So the emergency heat relay simply bypasses the outdoor thermostats. See Fig. 41. In the second method, the emergency heat relay is cycled directly by the thermostat mercury bulb. In this hookup, the relay is controlled by the thermostat first stage. The emergency heat relay energizes all of the auxiliary heat relays on a call for heat. See Fig. 42. Crankcase Heat In any mechanical refrigeration system, refrigerant tends to migrate to the coldest part of the equipment and condense there. In a heat pump, this coldest spot could be the compressor because it is usually outdoors. In addition, the oil in the compressor crankcase is capable of absorbing a high concentration of refrigerant. On compressor startup, there are two risks: (1) the liquid refrigerant, which is noncompressible, can be drawn into the cylinder, and (2) considerable oil can be entrained in the refrigerant and swept out of the crankcase through the changeover valve and dispersed in the piping and coils. So the emergency heat is controlled by the first stage of the thermostat. The emergency heat relay energizes all of the electric strip heaters so the heat and the indoor fan come on together as soon as the first stage calls for heat. So the migration of refrigerant to the crankcase is undesirable because it can interfere with system lubrication and because the liquid refrigerant must be kept from going through the compressor. With the first method, the fan remains on (being controlled by the first stage of the thermostat) and the electric heaters cycle on and off with the second stage. Adding a crankcase heater creates enough temperature differential to prevent this migration because the compressor is no longer the coldest part of the system so refrigerant does not migrate to it. In either case, a subbase indicator light is turned on whenever the function switch is in the emergency heat (EM.HT.) position. Another very simple method of detecting a compressor failure has been developed. It uses the voltage developed across the capacitor in a permanent split capacitor compressor motor. THERMOSTAT FUNCTION HEAT 2 SWITCH Compressor Fault Relay HEAT 1 COMPRESSOR The principle involved is that virtually all serious problems reduce the voltage across the motor capacitor. By carefully selecting the correct coil voltage, the normally closed relay does not pull in unless the proper voltage builds up across the capacitor, which brings on the SERVICE LED. See Fig. 43. AUXILIARY HEAT RELAY 1 OUTDOOR THERMOSTAT AUXILIARY HEAT RELAY 2 EMERGENCY HEAT RELAY CONTACT Here is how it works: • On a call for cooling, the thermostat makes R to Y, the contactor coil is powered, and the compressor motor turns on. • At the same time, the indicator light is energized. • As the motor gets up to speed—about one second, the fault relay sees enough voltage to pull in. Its normally closed contact opens and the indicator light goes out. • Anything that prevents the motor from running prevents the fault relay from pulling in. EMERGENCY HEAT RELAY M5833 Fig. 41. Emergency heat relay that bypasses the outdoor thermostats. COMPRESSOR MOTOR L1 24 V FAULT RELAY RUN R THERMOSTAT FUNCTION HEAT 2 SWITCH C HEAT 1 CAP. L3 EMERGENCY HEAT RELAY CONTACT START S COMPRESSOR Y R L L2 X AUXILIARY HEAT RELAY L1 (HOT) RISE EMERGENCY HEAT RELAY LED M5832 CONTACTOR Fig. 42. Emergency heat relay that energizes all of the auxiliary heat relays on a call for heat. THERMOSTATSUBBASE M5831 Fig. 43. Compressor fault relay schematic. 60-2485—8 28 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES CROSS REFERENCE 3. The following section lists the current T874 Trade replacements for T872 and T874 Multistage Thermostats. It also lists the Q674 Trade replacements for Q672 and Q674 Subbases. 4. 5. 6. All thermostats listed carry the Honeywell logo unless otherwise noted. When using the Cross Reference Charts, refer to the following instructions: 1. Locate and identify the existing thermostat and subbase model. 2. Refer to the Model Number column to find the model that matches the existing thermostat and subbase. 7. The Description column identifies certain characteristics of the existing device. The Trade Replacement column identifies the correct replacement device. The Remarks column lists any characteristics or adjustments to be made on the Trade replacement model. The Fig. No. column lists the wiring hookup used for the specific model number. The wiring diagrams follow the Cross Reference section. Refer to the circuit illustration that corresponds with the appropriate number. This figure illustrates the internal electric circuit for the desired model number. Table 6. T872-T874 Thermostat Cross Reference. Model Number T872A a T874 Trade Replacementa Description Remarks 1-stage heat, 1-stage cool A1006 Standard OEM T874A1036 A1014 72-78°F (22-26°C) stop; locking cover; no thermometer T874A1010 A1022 Heat anticipator set at 0.45A T874A1036 A1030 0.4A heat anticipator setting T874A1036 A1048 TRADELINE T874A1036 A1055 AAF logo; locking cover T874A1036 A1063 Climatrol logo T874A1036 A1071 Lennox logo; 0.5A heat anticipator setting T874A1036 A1089 Melco logo T874A1036 A1097 Westinghouse logo T874A1036 A1105 Amana logo; 1.2A heat anticipator setting T874A1036 A1113 Trane logo T874A1036 A1121 Airtemp (Chrysler) logo T874A1036 A1139 Singer logo; no. 02005384 T874A1036 A1147 American Standard logo T874A1036 A1154 Carrier logo and color; no. HH07AT074 T874A1036 A1162 General Electric logo; no. AY28X097 T874A1036 A1170 Sears logo; no. 4291441 T874A1036 A1188 Command-Aire logo T874A1036 A1196 Singer logo; Celsius scale; no. 02005521 T874A1036 A1204 Carteret logo T874A1036 A1212 General Electric; no. AY28X114; 72-78°F (22-26°C) stop T874A1010 A1220 Singer logo; no. 050240-01 T874A1036 A1238 Celsius scale T874A1036 A1246 TRADELINE; locking cover and adjustable locking T874A1150 lever stops A1253 Trane Comfort Corp T874A1036 A1261 TRADELINE; 72-78°F (22-26°C) stop; locking cover; no thermometer; meets DoD specs T874A1176 Use T874A1176 for Dept. of Defense (DoD) application. Use T874A1176 for Dept. of Defense (DoD) application. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 29 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Remarks A1279 General Electric logo; no. AY28X114A; 75°F stop; T874A1010 locking cover; no thermometer. Use T874A1176 for Dept. of Defense (DoD) application. A1287 T874A1036/ General Electric; no. AY28X097A; fan current shunt for auto fan in heating; heat anticipator set at Q674B1018 0.4A. Set thermostat stage 1 heat anticipator for total of fan and stage 1 primary control current draw. A1295 Lennox; Celsius scale T874A1036 A1303 Lennox logo; no. 64A0601; meets DoD specs T874A1176 A1311 Envirotron special; Celsius scale T874A1010 A1329 Carrier logo; Celsius scale; no. HH07AT074C T874A1036 A1337 Square D; no. HCD-3; heat anticipator set at 0.2A T874A1036 A1345 TRADELINE; Celsius scale T874A1010 A1352 Heat anticipator set 1.2A T874A1036 A1360 Friedrich logo; heat anticipator set at 0.2A T874A1036 A1378 Wesco logo; heat anticipator set at 0.8A T874A1036 T872B 1-stage heat, 2-stage cool B1005 Standard OEM B1013 0.4A heat anticipator setting T874B1019 B1021 TRADELINE T874B1019 B1039 Westinghouse logo T874B1019 B1047 American Standard logo T874B1019 B1054 Climatrol logo T874B1019 B1062 Carrier logo T874B1019 B1070 Trane logo T874B1019 B1088 Fedders logo T874B1019 T874B1019 B1096 Climatrol logo T874B1019 B1104 Carteret logo T874B1019 B1112 Singer logo; no. 050240-03 T874B1019 B1120 Celsius scale T874B1019 B1138 Singer logo; no. 02005711; locking cover and lever. T874B1019 B1146 Lennox logo; no. P-8-8895 T874B1019 B1153 Lennox logo; Celsius scale T874B1019 T872C a T874 Trade Replacementa Description 2-stage heat, 1-stage cool C1004 Standard OEM T874C1018 C1012 Heat anticipator set at 0.4A T874C1018 C1020 72-78°F (22-26°C) stop; locking cover; no thermometer; 42-88°F (6-31°C) setpoint range. T874C1141 C1038 TRADELINE T874C1018 C1046 American Standard logo T874C1018 C1053 Friedrich logo T874C1018 C1061 Lennox logo; no. P-8-8896 T874C1018 C1079 Westinghouse logo; stage 1 heat anticipator set at T874C1018 0.75A; stage 2 anticipator set at 1.2A C1087 Fast cycle performance on both heat stages; anticipator range 0.12-0.6A T874C1018 C1095 Payne logo; no. 0.1-0.175 T874C1018 Use T874C1141 for Dept. of Defense (DoD) application. Adjust anticipator faster for correct performance. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485—8 30 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number a T874 Trade Replacementa Description C1103 Amana logo; anticipator set at 1.2A T874C1018 C1111 Airtemp (Chrysler) logo T874C1018 C1129 Day and Night logo; no. 0.1-0.174 T874C1018 C1137 Fast cycle performance on both heat stages T874C1018 C1145 Rheem logo T874C1018 C1152 Ruud logo T874C1018 C1160 Climatrol logo T874C1018 C1178 Wesco logo T874C1018 C1186 Sears logo T874C1018 C1194 First Co. logo T874C1018 C1202 Carrier logo T874C1018 C1210 Carrier logo; Celsius scale T874C1018 C1228 0.4A heat anticipator setting T874C1018 C1236 Carrier logo; no. HH07AT070 T874C1018 C1244 Fraser-Johnson logo T874C1018 C1251 Trane logo T874C1018 C1269 Fedders logo T874C1018 C1277 Climatrol special T874C1018 C1285 Autogas logo T874C1018 C1293 Fedders logo T874C1018 C1301 Climatrol logo T874C1018 C1319 Command-Aire logo T874C1018 C1327 Melco logo; lock cover and levers T874C1018 C1335 Singer logo (Carteret) T874C1018 C1343 Singer logo; no. 050240-04 T874C1018 C1350 Celsius scale T874C1018 C1368 12°F (67°C) differential between heat 1 and heat 2 T874C1125 C1376 AAF logo; locking cover; 72-78°F (22-26°C) stop T874C1018 C1384 Servel logo T874C1018 C1392 TRADELINE; fast cycle performance on both heat T874C1018 stages. C1400 72-78°F (22-26°C) stop; locking cover; no thermometer; meets DoD specs T874C1141 C1418 Solaron logo T874C1018 C1426 Lennox logo; no. 42C04; four LEDs None C1434 Carrier logo; no. HH07AT070C; Celsius scale T874C1018 C1442 Goettl logo T874C1018 C1459 Goettl logo; used with Q672N1001, N1019 None C1467 Lennox logo; Celsius scale T874C1018 C1475 Tappan logo; no. 080-13708-37 T874C1018 C1483 Fasco logo; no. 1230-8161 T874C1018 C1491 Lennox logo; no. 64A0501; locking cover; no thermometer; meets DoD specs T874C1141 Remarks Adjust anticipator faster for correct performance. Adjust anticipator faster for correct performance. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 31 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number T874 Trade Replacementa Description C1509 Fedders logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X, K=E; remove Y-W1 jumper. C1517 Climatrol logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X, K=E; remove Y-W1 jumper. C1525 Square D logo; no. HCD-2 T874C1018 C1533 Airtemp logo T874C1018 C1541 Airtemp logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X, K=E; remove Y-W1 jumper. C1566 TRADELINE; Celsius scale T874C1018 Replacement has °F scaleplate. C1574 Whalen special; used with Q672B1269 None C1582 Lennox; meets DoD None C1590 Singer; 8°F (4.4°C) differential between stage 1 and stage 2 T874C1125 Replacement has 2°F (1° C) differential between H1 and H2. C1608 Singer logo; no. 02005784 8°F (4.4°C) differential T874C1125 between stage 1 and stage 2 Replacement has 2°F (1°C) differential between H1 and H2. C1616 Celsius scale; stop set at 23°C None Add 4074ECK adjustable stop. C1624 Heat Wave logo; no. 0360-116 T874C1018 C1632 York logo; heat anticipator set at 0.2A T874C1018 C1640 Heat anticipator set at 0.4A T874C1018 C1665 Wesco logo; heat anticipator set at 0.8A T874C1018 C1673 Wards logo; used with Q672B1285, B1293 Gas systems: T874C1018/ Q674B1034 Electric systems: T874C1018/ Q674B1075 C1681 Lechauffage Urbain logo; Celsius scale T874C1018 C1699 Duotherm logo; used with Q672E1068 or Q672F1000 T874C1018 C1707 Sigler logo; used with Q672N1027 None Westinghouse logo T874C1018 C1715 T872D a Remarks Adjust anticipator faster for correct performance. See subbase description for replacement information. 2-stage heat, 2-stage cool D1003 Standard OEM T874D1165 D1011 TRADELINE T874D1165 D1029 Westinghouse logo T874D1165 D1037 Climatrol logo T874D1165 D1045 Lennox logo; no. P-8-8897; used with Q672E1191. T874D1165 D1052 York logo T874D1165 D1060 Singer logo; no. 02005385 T874D1165 D1078 Rheem logo T874D1165 D1086 Rudd logo T874D1165 D1094 York logo; locking cover T874D1165 D1102 American Standard logo T874D1165 D1110 ITT logo T874D1165 D1128 Carrier logo T874D1165 D1136 No anticipator on stage 1 cool; used with Q672C1029 T874D1165 When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485—8 32 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number D1144 Carrier logo; no. HH07AT072 T874D1165 D1151 General Electric logo; no. AY28X098; 0.4 heat anticipator setting T874D1165 D1169 Airtemp (Chrysler) logo; used with Q672E1118 T874D1165/ Q674E1049 D1177 Trane logo T874D1165 D1185 Dunham-Bush logo T874D1165 D1193 Fedders logo T874D1165 D1201 Climatrol logo T874D1165 D1219 Command-Aire logo T874D1165 D1227 Singer logo; no. 02005522; Celsius scale T874D1165 D1235 Singer logo; (Carteret) T874D1165 D1243 Friedrich logo T874D1165 D1250 Singer logo; no. 050240-02 T874D1165 D1268 Airtemp logo T874D1165 D1276 Celsius scale T874D1165 D1284 Solaron T874D1165 D1292 Tokyo Carrier logo; no. HH07AT072C; Celsius scale T874D1165 D1300 SUPER TRADELINE T874D1165 D1318 General Electric logo; no. AY28X098A; fan current T874D1165/ shunt for auto fan in heating. Q674B1075 D1326 General Electric logo; locking cover 72-78°F (22-26°C) stop; fan current shunt for auto fan in heating. T874D1165 D1334 Lennox logo; Celsius scale T874D1165 D1342 Tappan logo; no. 080-13708-32 T874D1165 D1359 Singer logo; no. 02005740; Celsius scale; 6.6°C differential between H1 and H2. T874D1165 D1367 Friedrich logo; no. 600-580-23 T874D1165 D1375 Singer logo; no. 02005713; Celsius scale; controls None 2 separate heat/cool circuits; used with Q674G1017 D1383 TRADELINE; Celsius scale D1391 Singer logo; no. 02005712; controls two separate None heat/cool circuits; used with Q674G1017 12°F (7°C) differential between H1 and H2 T874D1165 D1417 Fedders logo T874D1165 D1425 Climatrol logo T874D1165 D1433 Singer logo; no. 02005785; 8°F (4.4°C) differential T874D1165 between H1 and H2 D1441 American Air Filter T874D1165 Carrier; no. HH07AT072-03; Celsius scale T874D1165 D1474 Remarks Wiring differences (old=new): A=W1; set H1 anticipator to 1.2A. Only 2°F (1°C) differential between H1 and H2. T874D1165 D1409 T872E a T874 Trade Replacementa Description 2-stage cool E1002 Standard OEM T874E1016 E1010 TRADELINE T874E1016 E1028 Westinghouse logo T874E1016 When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 33 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number E1036 American Standard logo T874E1016 E1044 York logo; locking cover T874E1016 E1051 ITT logo T874E1016 E1069 Climatrol logo T874E1016 E1077 Airtemp (Chrysler) logo T874E1016 E1085 Lennox logo T874E1016 E1093 Trane logo T874E1016 E1101 Dunham-Bush logo T874E1016 E1119 Fedders logo T874E1016 E1127 Climatrol logo T874E1016 E1135 General Electric logo; no. AY28X108 T874E1016 E1143 Lennox logo; Celsius scale T874E1016 E1150 Celsius scale T874E1016 E1168 Airtemp logo T874E1016 T872F 2-stage heat F1001 Standard OEM T874F1015 F1019 TRADELINE T874F1015 F1027 Lennox logo; fast cycle heat anticipator T874C1018 F1035 Luxaire logo; fast cycle performance on both heat T874C1018 stages. F1043 York logo; locking cover; used with M839. T874C1018 F1050 Raehco logo T874F1015 F1068 Fast cycle performance on both heat stages. T874C1018 F1076 Wesco logo T874F1015 F1084 Lennox logo T874F1015 F1092 Auto Gas logo T874F1015 F1100 Celsius scale T874F1015 F1118 Lennox logo; Celsius scale T874F1015 F1126 Stages 1 and 2 heat electrically isolated; used with None Q672D1002 F1134 Square D logo; HCD-4 T874F1015 F1159 Wesco logo; heat anticipator set at 0.8A T874F1015 F1167 York logo T874F1015 F1175 Oneida Heater logo; no. 30A0287-01; used with Q672K1012. T874F1015/ Q674K1026 T872G a T874 Trade Replacementa Description Remarks M839 draws 0.72A; set adjustable heat anticipator to setting of 0.9A for proper cycle rate. Heat pump models; 2-stage heat, 1-stage cool, 1-stage changeover. G1000 Fast cycle performance stage 2 heat; fixed Y594G1252 anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1018. Wiring differences (old=new): W=W2, X1=X. G1018 Adjustable anticipator stage 2 heat; fixed Y594G1393 anticipator stage 1 heat and cool; changeover with cooling; used with Q672E1027. Wiring differences (old=new): Y1=O, Y2=Y. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485—8 34 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number a T874 Trade Replacementa Description Remarks G1026 Lennox logo; fast cycle performance; stage 2 heat; None fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672E1019, F1067. See subbase description for replacement information. G1034 Westinghouse logo; adjustable anticipator stage 2 Y594G1252 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1091, F1141, F1257 or Q672J1013, J1062. Wiring differences (old=new): W=W2. G1042 York logo; fixed anticipator on all stages heat and cool; changeover with cooling; used with Q672J1021. G1059 TRADELINE; no anticipator stage 2 heat; fixed Y594G1161 anticipator stage 1 heat and cool; changeover with cooling; used with Q672J1039 outdoor reset. Designed for use on General Electric heat pumps. G1067 Lennox logo; no. P-8-11222; fast cycle performance; stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672E1142, F1083. See subbase description for replacement information. G1075 Carrier logo; adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672J1054, L1052. See subbase description for replacement information. G1083 Y594G1252 Adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158. G1091 Lennox logo; same as T872G1026 except meets DoD specs. See subbase description for replacement information. G1109 Y594G1252 Tappan logo; no. 080-13708-52; adjustable anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1117. Wiring differences (old=new): C=X. G1117 Changeover; used with Q672F1125. Wiring differences (old=new): C=X. G1125 Lennox logo; no. 63A0401; Celsius scale; isolated None auxiliary heat power circuit; fast cycle anticipator stage 2 heat. G1133 Rheem logo; no. RXMT-B71; adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158, F1232. G1141 Y594G1252 Ruud logo; adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158. G1158 Carrier logo; same as T872G1075. Except DoD styling. G1166 BDP used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X. G1174 BDP used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X. G1182 Carrier; no. HH07AT071C; Celsius scale; used with Q672L1052, J1054. G1190 Tappan; no. B13708-57; used with Q672L1078 for None 8 and 10 ton heat pumps with 2 compressors. Y594G1567 Y594G1252 Y594G1252 See subbase description for replacement information. See subbase description for replacement information. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 35 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number T874 Trade Replacementa Description G1208 Marvair logo; special for Crispaire; used with Q672F1166, F1323. Y594G1393 G1216 Janitrol logo; no. 26G05; stage 2 heat anticipator set at 1.2A; used with Q672F1117. Y594G1252 G1224 TRADELINE; adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover in cool; used with Q672F1208. Y594G1419 G1232 Heat Wave (Southwest Mfg.) logo; stage 2 heat anticipator set at 1.2A; used with Q672F1224. G1240 Lennox; fast cycle anticipator stage 2 heat; used with Q672F1240. None G1257 Carrier logo; no. HH07AT073; used with Q672L1169 (HH93AZ071). None G1265 Addison logo; used with Q672F1265. Y594G1252 G1273 Carrier logo; (DoD model); 68°F (20°C) maximum heating; 78°F (26°C) minimum cooling; used with Q672L1052, J1054 G1281 Wesco logo; used with Q672F1265. Y594G1252 G1299 York logo; meets DoD specs; used with Q672L1177. Y594G1567 G1307 Carrier; no. 38EQ1900; Celsius; used with Q672J1054, L1052. G1315 Luxaire special; stage 2 heat anticipator set to 1.2A; used with Q672F1281. Y594G1252 G1323 Lennox special; used with Q672L1201 and C815A1013. None G1331 York; used with Q672J1021. Y594G1567 Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required. G1356 Westinghouse; used with Q672L1219. T874D1165/ Q674F1022 Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required. G1364 York; used with Q672D1077. None G1372 Tappan/Janitrol logo; no. B-13708-521; used with Q672F1117. Y594G1252 G1398 York logo; no. 025-21454C; used with Q672J1021. Y594G1567 T872H Wiring differences (old=new): C=X. Wiring differences (old=new): C=X. See subbase description for replacement information. Wiring differences (old=new): C=X. See subbase description for replacement information. Wiring differences (old=new): C=X. Heat pump model; 1 stage heat, 1 stage cool, 1 stage changeover. H1009 Command-Aire logo; fixed anticipator stage 1 heat Y594H1012 and cool; changeover with cooling; used with Q672C1086. H1017 Friedrich logo. Y594H1012 H1025 Friedrich logo; Celsius. Y594H1012 T872M 1 stage heat, 1 stage cool with stage 2 heat factory set at 60°F (16°C). M1003 Standard OEM; used with Q672D and external switching means. T872N Heat pump model; 2-stage heat, 1-stage cool plus changeover, changeover in heat mode. N1002 a Remarks T874C1125 T874C1125 has 12°F (6.7°C) differential between stage 1 and stage 2 heat. None When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485—8 36 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number N1010 Williamson logo; adjustable anticipator stage 1 and T874N1016/ Q674F1220 2 heat; fixed anticipator stage 1 cool; used with Q672F1133 or F1315. N1028 TRADELINE heat mode changeover; used with Q672F1216. T874N1016 N1036 Bard; used with Q672F1299. T874N1016/ Q674F1220 N1044 Thermotron logo; 1st stage changeover heat mode; used with Q672F1299. T874N1016/ Q674F1220 T872Q Remarks 1-stage heat; used with another T872 for heating setback. Q1009 Standard OEM T874C1125 Q1017 York logo T874C1125 Q1025 ITT logo None Q1033 Lennox logo; no. P-8-8899. None Q1041 Lennox logo; no. 63A6401. None T872R a T874 Trade Replacementa Description Replacement only good for 1-stage heat and 1-stage cool applications. Heat pump model; 2-stage heat, 1-stage cool, manual changeover. R1008 Y594R1425 Fixed anticipator stage 1 heat and cool; no anticipator stage 2 heat; changeover with cooling; used with Q672B1046. Wiring differences (old=new): W=W2; W1-Y1 jumper required. R1016 Addison same as T872R1008; used with Q672B1103. Wiring differences (old=new): W=W2; W1-Y1 jumper required. R1024 Lennox logo; fast cycle stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; used with Q672B1160 and Q672L1003. R1032 York logo; fixed anticipator stage 1 and 2 heat and Y594R1664 stage 1 cool; changeover with cooling; used with Q672L1011. R1040 Lennox logo; fast cycle stage 2 heat; fixed anticipator stage 1 heat and cool; isolated stage 2 heat switch; changeover with cooling; used with Q672B1202 no. P-8-11221, Q672L1029 R1057 TRADELINE; fixed anticipator stage 1 heat and cool; no anticipator stage 2 heat; changeover on cooling; used with Q672L1037; outdoor reset. Y594R1763 R1065 Adjustable anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover on cooling; used with Q672L1045. Y594R1243 R1073 Lennox logo; no. 63A0301; Celsius scale; separate auxiliary heat power circuit; fast cycle stage 2 heat antic. None R1081 Ruud logo; same circuit as T872R1065; used with Y594R1243 Q672L1045, L1136. R1099 Dunham Bush special; used with Q672L1060, L1383. Y594R1243 R1107 Rheem; no. RXMT-B70; used with Q672L1045, L1136. Y594R1243 R1115 Friedrich logo; fixed anticipator; used with Q672B1244, L1086. Y594R1425 See subbase description for replacement information. See subbase description for replacement information. Designed for use on General Electric heat pumps. Wiring differences (old=new): A=T. See subbase description for replacement information. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 37 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6. T872-T874 Thermostat Cross Reference. Model Number Remarks R1123 York logo; no. 025-21453C; Celsius scale. R1131 Lennox logo; separate auxiliary heat power circuit; None fast cycle stage 2 heat anticipator; outdoor reset; used with Q672L1144, C815A1013. R1149 Westinghouse logo; adjustable stage 2 heat anticipator; cooling changeover; fixed anticipator stage 1 heat and cool; used with Q672L1110, L1128, L1151. Y594R1243 Wiring differences (old=new): W=W2. R1156 Marvair logo; used with Q672L1094, L1250. Y594R1243 Replacement has auto fan in Emergency Heat mode. R1164 Bard; used with Q672L1185. Y594R1243 R1172 Heil Quaker; used with Q672L1193. Y594R1243 R1180 York; Celsius; used with Q672L1011. Y594R1664 R1198 TRADELINE; used with Q672L1227 Y594R1243 R1206 For use with W89; used with Q672L1235. None R1214 Intertherm logo; used with Q672L1276. Y594R1300 R1222 York logo; used with C815A1039; adjustable anticipator stage-2 heat; used with Q672L1284 Y594R1672 R1230 Amana logo; no. C62397-1; used with Q672L1300, W89. None R1255 Singer logo; used with Q672L1326 and W89. None R1271 Westinghouse logo; used with Q672L1375 and W89. Y594R1664 R1297 York; Celsius scale; used with Q672L1011. None R1305 Used with Q672L1235 and W89. None R1321 Duotherm logo; used with Q672L1409, and W89. None R1339 Williamson; used with Q672L1391. Y594R1243 T872S S1005 T872T T1004 T872W a T874 Trade Replacementa Description Y594R1664 Wiring differences (old=new): B=X, W=W2. Wiring differences (old=new): W1=B, Z=L, K=E. Heat pump model; 2-stage heat plus changeover, 1-stage cool. Westinghouse logo; adjustable anticipator stage 1 T874C1018/ and 2 heat; fixed anticipator stage 1 heat; Q674C1058 changeover with heating: used with Q672C1045 Wiring differences (old=new): V=RC-RH, F=G, C=Y1, Z=B, H2=W2; W1-Y1 jumper required. 1-heat stage, 1-vent and 2-cool stages. Trane logo; used with Q672B1129. None 3-heat stages, 2-cool stages, manual changeover W1019 Lennox logo; no. 52C7501; used with Q672L1342 None and C815A1013. W1027 Westinghouse logo; used with Q672L1268 and C815A1021. None W1035 TRADELINE; used with C815A1043 and Q672B1251. Y594W1014 When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase. 60-2485—8 38 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Q672A A1005 Q674 Trade Replacementa Description System: HEAT-AUTO-COOL, Fan: AUTO-ON Standard OEM Q674A1019 A1013 TRADELINE Q674A1019 A1021 RC-RH jumper Q674A1019 RC-RH jumper required. RC-RH jumper; Chek Lite Q674A1019 RC-RH jumper required. A1039 Q672B System: HEAT-OFF-COOL, Fan: AUTO-ON B1004 Standard OEM Q674B1034 B1012 Isolated G terminal. Q674B1018 B1020 System: HEAT-OFF-RESET-COOL Q674B1034 B1038 TRADELINE Q674B1034 B1046 Heat pump circuit; used with T872R1008. Y594R1425 Wiring differences (old=new): W1=Y1, W=W2. B1053 RC-RH jumper Q674B1034 RC-RH jumper required. B1061 Chek Lite Q674B1034 B1079 Auto fan operation in heat and cool. Q674B1075 B1087 Carrier no. HH93AZ078; RC-RH jumper. Q674B1075 B1095 Carrier no. HH93AZ084; RC-RH jumper. Q674B1034 B1103 Addison; heat pump circuit; used with T872R1016. Y594R1425 B1111 Carrier no. HH93AZ080; isolated G terminal. Q674B1018 B1129 Trane special circuit; used with T872T1004. None B1137 RC-RH jumper; isolated G terminal. Q674B1018 RC-RH jumper required. B1145 Fedders special Q674B1034 RC-RH jumper required. B1152 Fedders special; auto fan operation in heat and cool. Q674B1075 B1160 Lennox; heat pump circuit; used with T872R1024; includes compressor lockout in EM. HT. Y594R1243 B1178 General Electric no. AY28X107; auto fan operation in heat and cool. Q674B1075 B1186 Trane; isolated G terminal; Filter LED. Q674B1018 B1194 General Electric no. AY28X124; auto fan operation in heat and cool. Q674B1075 Set T874 stage-1 anticipator for combined load of heat relay and fan relay. B1202 Lennox no. P-8-11223; heat pump circuit; used with T872R1040. Y594R1243 Wiring differences (old=new): V-VR=R, M=Y, Y=W2, F=G, R=O. B1228 General Electric no. BAY28X137; isolated G terminal. Q674B1018 B1236 Carrier no. HH-93AZ079; RC-RH jumper; LOCKOUT LED indicates compressor lockout switch activated. Q674B1034 RC-RH jumper; LED cannot be provided in TRADELINE model. B1244 Friedrich; heat mode changeover; used with T872R1115. T874C1018/ Q674B1034 Wiring differences (old=new): C=no connection; RC-RH and W1-Y1 jumpers required. B1251 Used with T872W1035 and C815A1043. Y594W1014 B1210 a Remarks Used system off as reset position. Wiring differences (old=new): W=W2; W1-Y1 jumper required. Wiring differences (old=new): V-VR=R, M=Y, Y=W2, F=G, R=O. None When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 39 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Q674 Trade Replacementa Description B1269 Whalen; Hi-Lo fan switch; constant fan in heat and cool system switch positions; used with T872C1574. None B1277 Square D no. HCB-5. Q674B1034 B1285 Wards; RC-RH and F-W3 jumpers; used with T872C1673. Gas Furnace: T874C1018/ Q674B1034 Electric Furnace: T874C1018/ Q674B1075 B1293 Q672C Adjust anticipator faster for correct performance. Same as Q672B1285 System: OFF-AUTO, Fan: AUTO-ON C1003 Standard OEM Q674C1058 C1011 Westinghouse; RC-RH jumper. Q674C1058 RC-RH jumper required. C1029 W1-Y2 jumper; for heat pump; used with T872D1136. Q674E1049 Replacement has heat/cool system switching. C1037 Chrysler Airtemp; System: COOL-OFF-AUTO. Q674C1058 C1045 Westinghouse; heat pump; used with T872S1005. T874C1018/ Q674C1058 Wiring differences (old=new): V=RC-RH, F=G, C=Y1, Z=B, H2=W2; W1-Y1 jumper required. C1052 Isolated stage 2 heat circuit for dc electric heat relay. Recontrol Use T874G1246/Q674F1212 which adds HEAT-COOL-EM.HT. system switch. C1060 Fedders special. Q674C1058 C1078 General Electric no. AY28X109. Q674C1058 C1086 Command-Aire; heat pump; used with T872H1009. Y594H1012 C1102 TRADELINE Q674C1058 Q672D System: None. Fan: None. D1002 Standard OEM; used with T872F1126. Q674D1040 D1010 Lennox special. None D1028 Carrier; RC-RH jumper. None D1036 Carrier no. HH93AZ070; RC-RH jumper. Q674D1040 D1044 General Electric no. AY-28X100. None D1069 Square D no. HCB-4. None D1077 York; used with T872G1364. None D1085 TRADELINE Q674D1040 Q672E a Lennox no. 41C96; used with T872C1673. Remarks RC-RH jumper required. System: OFF-HEAT-AUTO-COOL Fan: AUTO-ON E1001 Standard OEM Q674E1049 E1019 Lennox no. P-8-8892; heat pump; cool mode changeover; used with T872G1026. T874D1165/ Q674B1075 E1027 Heat pump circuit; W1-Y2 jumper; cool mode changeover; used with T872G1018. Y594G1393 Wiring differences (old=new): Y1=O, Y2=Y. E1035 Heat pump circuit; W1-Y2 jumper; cool mode changeover. Y594G1393 Wiring differences (old=new): Y1=O, Y2=Y. E1043 Heat pump circuit; heat mode changeover. Q674E1049 Wiring differences (old=new): W1=B, W2=W1; W1-Y1 jumper. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 60-2485—8 40 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number Remarks E1050 TRADELINE Q674E1049 E1068 RC-RH jumper; used with T872C1699. Q674E1049 RC-RH jumper required. E1076 RC-RH internal jumper; EM. HT. LED. Q674E1049 RC-RH jumper required. E1084 Carrier no. HH93AZ076; RC-RH jumper. Q674E1049 RC-RH jumper required. E1092 Carrier no. HH93AZ082; RC-RH jumper; B terminal; isolated G terminal. Q674E1049 E1100 General Electric no. AY28X099. Q674E1049 E1118 Airtemp; heat pump; used with T872D1169. T874D1165/ Q674E1049 Wiring differences (old=new): A=W1; set H1 anticipator to 1.2A. E1126 Common R terminal. Q674E1049 RC-RH jumper required. E1134 ITT Nesbitt; RC-RH jumper; O and B terminals; Q674E1049 isolated G terminal. E1142 Y594G1252 Lennox no. P-8-11224; heat pump; V-VR jumper; cool mode changeover; used with T872G1067. E1159 Carrier no. HH93AZ077; RC-RH jumper; LOCKOUT LED indicates activation of compressor lockout switch. Q674E1049 E1167 Square D no. HCB-2; Chek Lite. Q674E1049 E1183 Square D no. HCB-3. Q674E1049 E1191 Lennox; HIGH and LOW LEDs; used with T872D1045. Q674E1049 Q672F a Q674 Trade Replacementa Description Wiring differences (old=new): V-VR=R, Y=W2, R=O, M=Y, F=G. RC-RH jumper required; no LED in TRADELINE model. No LEDs on replacement. System: EM. HT.-HEAT-AUTO-COOL-OFF Fan: AUTO-ON. F1000 With EM. HT. LED; used with T872C1699. Q674F1022 Remove W3-X2 jumper to E-X2. F1018 Heat pump; heat mode changeover; Chek Lite; used with T872G1000. Y594G1252 Wiring differences (old=new): W=W2, X1=X. F1026 Chek Lite; W2-X2 jumper. Q674F1022 F1034 Airtemp; EM. HT. LED; RC-RH and X2-E jumpers. Q674F1022 F1042 W2-X2 jumper; Chek Lite. Q674F1022 F1059 Carrier no. HH93AZ074; EM. HT. LED. Q674F1022 F1067 Lennox; heat pump; cool mode changeover; EM. HT. LED; used with T872G1026. None F1075 Heat pump circuit; EM. HT. LED; 2 terminal; RC- None RH jumper. F1083 Lennox no. P-8-11225; heat pump; V-VR jumper; cool mode changeover; EM. HT. LED; used with T872G1067. None F1091 Westinghouse; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1034. Y594G1252 Wiring differences (old=new): W=W2. F1109 Airtemp no. 3778567ACC; R-X2 jumper; EM. HT. LED. Q674F1022 R-X2 jumper required. F1117 Tappan no. 080-13708-53; heat pump; EM. HT. Y594G1252 LED; cool mode changeover; compressor lockout and auto fan in EM. HT.; used with T872G1109, G1216, G1372. If RC-RH jumper removed on Q672F1034, Q674F1022 does not replace. Remove W2-X2 jumper to E-X2; X terminal same as C. Wiring differences (old=new): C=X. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 41 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number F1125 BDP no. 3442DP90; used with T872G1117, G1166, G1174. Y594G1252 F1133 Williamson; heat pump; EM. HT. LED; heat mode changeover; compressor lockout in EM. HT.; used with T872N1010. T874N1016/ Q674F1220 F1141 Westinghouse; EM. HT. LED; auto fan in EM. HT.; used with T872G1034. Y594G1252 F1158 Rheem Ruud; heat pump; EM. HT. LED; cool Y594G1252 mode changeover; compressor lockout in EM. HT.; used with T872G1083, G1133, G1141; auto fan in EM. HT. F1166 Crispaire; EM. HT. LED; used with T872G1208. Y594G1252 F1174 Carrier no. HH93AZ081; EM. HT. LED. Q674F1022 F1182 Square D no. HCB-1; Chek Lite; R-X2 jumper; System: Aux. Heat replaces EM. HT. Q674F1022 F1190 EM. HT. LED; X2-E and RC-RH jumpers. None F1208 TRADELINE; cool mode changeover; EM. HT. LED; used with T872G1224. Y594G1419 F1216 TRADELINE; heat mode changeover; EM. HT. LED; used with T872N1028. T874N1016/ Q674F1220 F1224 Heatwave (Southwest Mfg.); compressor lockout in EM. HT.; EM. HT. LED; used with T872G1232. Y594G1252 F1232 Rheem; cool mode changeover; EM. HT. and AUX. HEAT LEDs; compressor lockout in EM. HT.; used with T872G1133. Y594G1252 F1240 Lennox; cool mode changeover; EM. HT. and SERVICE LEDs; used with T872G1240. None F1257 Westinghouse; cool mode changeover; EM. HT. and AUX. HEAT LEDs; auto fan in EM. HT; used with T872G1034. Y594G1252 F1265 Wesco Addison; Chek and EM. HT. LEDs; used Y594G1252 with T872G1281, G1265. F1273 Southwest special; no. 0361-136; W2-X2 jumper. None F1281 Luxaire special; used with T872G1315. Y594G1252 F1299 Bard special; used with T872N1036, N1044. T874N1016/ Q674F1220 F1315 Williamson special; used with T872N1010. T874N1016/ Q674F1220 Crispaire special; used with T872G1208. Y594G1252 F1323 Q672G a Q674 Trade Replacementa Description Remarks Wiring differences (old=new): C=X. Wiring differences (old=new): W=W2. R-X2 jumper; add monitor switch between X1 and low side of power. Wiring differences (old=new): W=W2. Wiring differences (old=new): C=X. System: OFF-AUTO. Fan: None. G1009 Standard OEM Q674G1070 G1017 Singer; O-B jumper; used with T872D1375. Q674G1070 G1025 Includes O and B terminals. Q674G1070 G1033 General Electric no. AY28X102. Q674G1070 G1041 Singer no. 02005649; French wording; O-B jumper. Q674G1070 Less French wording. G1066 SLI-Mammoth; heat pump; heat mode changeover. Q674G1070 Connect fan (G) wire to Y1 terminal; B-O and RC-RH jumpers. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 60-2485—8 42 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number G1074 Singer no. 02005754; X1 and X2 terminals for field-added indicator lights; used with T872D1375. None G1082 Singer no. 02005792; X1 and X2 terminals for field-added indicator lights; used with T872D1375. None G1090 TRADELINE; B and O terminals. Q674G1070 Q672H H1008 Q672J Used with T872. None System: EM. HT.-AUTO-OFF Fan: AUTO-ON. With EM. HT. LED; used with T872C or D. None J1013 Westinghouse; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1034. Y594G1252 J1021 Y594G1567 York; heat pump; EM. HT. LED; cool mode changeover; compressor lockout and auto fan in EM. HT.; E-W jumper; used with T872G1042, G1331, G1398. J1039 Heat pump; EM. HT. and AUX. HEAT LEDs; Y594G1161 cool mode changeover; compressor lockout and auto fan in EM. HT.; used with T872G1059. J1047 Singer no. 02005699; heat pump; EM. HT. LED; Q674F1022 heat mode changeover. J1054 Carrier no. HH93AZ073A; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1075, G1182, G1307. J1062 Westinghouse; EM. HT. and AUX. HEAT LEDs; Y594G1252 used with T872G1034. Y594G1252 Designed for use on General Electric heat pumps. Wiring differences (old=new): C=X. Wiring differences (old=new): W=W2. System: OFF-HEAT-AUTO-COOL. Fan: None. K1004 Carrier no. HH93AZ072. K1012 Oneida Heater no. 30A0288-01; System: OFF- T874F1155/ WOOD-WOOD/OIL-OIL; used with T872F1175. Q674K1026 Q672L Remarks System: OFF-ON Fan: NIGHT INT.-DAY CONT. J1005 Q672K a Q674 Trade Replacementa Description Q674E1049 Fan switch does not function. System: EM. HT.-HEAT-OFF-COOL. Fan: ON-AUTO. L1003 Lennox; heat pump; EM. HT. LED; cool mode changeover; used with T872R1024. Y594R1425 L1011 York; heat pump; EM. HT. LED; cool mode Y594R1664 changeover; compressor lockout and auto fan in EM. HT.; used with T872R1032, R1180, R1297. L1029 Lennox no. P-8-11226; heat pump; EM. HT. LED; V-VR jumper; cool mode changeover; compressor lockout in EM. HT.; used with T872R1040. L1037 Heat pump; EM. HT. and AUX. HT. LEDs; cool Y594R1763 mode changeover; compressor lockout and auto fan in EM. HT.; used with T872R1057. L1045 Rheem; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; auto fan in EM. HT; used with T872R1065, R1081, R1107. Y594R1425 Wiring differences (old=new): V-VR=R, M=Y, Y=W2, F=G, R=O. Wiring differences (old=new): A=T; designed for used on General Electric heat pumps. Y594R1243 When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 43 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number a Q674 Trade Replacementa Description Remarks L1052 Carrier no. HH93AZ075; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1075, G1182, G1273, G1307. Y594R1615 L1060 Dunham Bush; EM. HT. LED; used with T872R1099. Y594R1243 L1078 Tappan no. B13708-58; heat pump; EM. HT. LED; cool mode changeover; compressor lockout in EM. HT.; EM. HT. relay provides fan operation in EM. HT.; used with T872G1190. None L1086 Friedrich; heat mode changeover; EM. HT. LED; Y594R1243 used T872R1115 with L terminal. Wiring differences (old=new): X2=E, C=X. L1094 Crispaire; W2-H jumper; EM. HT. LED; used with T872R1065, R1156. Replacement has auto fan in Emergency Heat mode. L1102 Fedders; heat mode changeover; EM. HT. LED; Y594R1425 used with T872C1509, C1517, C1541. Wiring differences (old=new): K=E, C=X; remove Y-W1 jumper. L1110 Westinghouse; EM. HT. LED; used with T872R1149. Y594R1243 Wiring differences (old=new): W=W2. L1128 Westinghouse; EM. HT. LED; used with T872R1149. Y594R1243 Wiring differences (old=new): W=W2. L1136 Y594R1243 Rheem no. 41-20796-07; cool mode changeover; EM. HT. and AUX. HT. LEDs; used with T872R1081, T872R1107. L1144 Lennox; V-VR jumper; EM. HT. and SERVICE LEDs; isolated stage 2 heat; used with T872R1131, C815A1013. None L1151 Westinghouse; AUX. HT. and EM. HT. LEDs; used with T872R1149. Y594R1243 L1169 Carrier no. HH93AZ071; EM. HT. LED; used with T872G1257 (HH07AT073). None Y594R1243 L1177 York; DoD; EM. HT. LED; used with T872G1299. Y594G1567 L1185 Bard; used with T872R1164. Y594R1243 L1193 Heil Quaker no. NAXA001TS01; used with T872R1172. Y594R1243 L1201 Lennox special; no. 1485701; used with T872G1323. None L1219 Westinghouse special; used with T872G1356. T874D1165/ Q674F1022 L1227 Heat pump; used with T872R1198. Y594R1243 L1235 Intertherm; used with T872R1206, R1305. None L1250 Crispaire special; used with T872R1156 and C815A1021. Y594R1243 L1268 Westinghouse special; used with T872W1027 and C815A1021. None L1276 Intertherm special; used with T872R1214. Y594R1300 L1284 York special; used with T872R1222. Y594R1672 L1300 Amana special; no. C62345-1; used with T872R1230. None L1326 Singer; used with T872R1255. None Wiring differences (old=new): C=X. Wiring differences (old=new): W=W2. Wiring differences (old=new): B=X, W=W2. Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2-W2 jumpers required. Wiring differences (old=new): W1=B, Z=L, K=E. When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 60-2485—8 44 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7. Q672-Q674 Subbase Cross Reference. Model Number L1342 Lennox no. 52C7601; used with T872W1019 and C815A1013. None L1375 Westinghouse; used with T872R1271, W89. None L1383 Dunham Bush; used with T872R1099. Y594R1243 L1391 Williamson; used with T872R1339. Y594R1243 L1409 Duotherm special; used with T872R1321, W89. None Q672N Goettl; heat pump; heat mode changeover; evaporative cooler circuit; Fan: AUTO-ON; System: AUTO; used with T872C1459. None N1019 Goettl; heat pump; heat mode changeover; evaporative cooler circuit; W1-Y1 jumper; used with T872C1459. None N1027 Siegler special; used with T872C1707. None P1009 Remarks System: OFF-HEAT-COOL-EVAP. N1001 Q672P a Q674 Trade Replacementa Description System: EM. HT.-HEAT-COOL. Carrier special; no. HH93AZ069; used with T872G1075 (HH07AT071). Y594R1243 Replacement has OFF system switch position When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase. 45 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. T874A A1002 Remarks 1-stage heat, 1-stage cool. 44, 65 Honeywell logo; Standard OEM; used with Q674B1331. T874A1036 A1010 44 Honeywell logo; includes Allen wrench and screws to lock cover; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers. T874A1010 A1028 44 Honeywell logo; heat anticipator factory set at 0.4A. T874A1036 A1036 44 Honeywell logo; TRADELINE® model; includes Allen wrench and screws to lock cover; field adjustable locking levers. T874A1036 A1044 44 Obsolete. AAF/Snyder General logo; part no. 4ELN3006C; °F/°C scaleplate. T874A1036 Replacement has °F scaleplate. A1051 44 Lennox logo; part no. 12F9901; °F/°C scaleplate; heat anticipator set at 0.45A. T874A1036 Replacement has °F scaleplate. A1069 44 Obsolete. Westinghouse logo; used with Q674A-E,G. T874A1036 A1077 46, 82 Obsolete. Amana Air Conditioning logo; part no. D68535-1; heat anticipator factory set at 1.2A; used with Q674B1075, E1056; used in Y594A1001, A1019. T874A1036 A1085 44, 46, Obsolete. Trane logo; part no. 13510451; used with 55, 66 Q674B1018, B1075, D1008. T874A1036 A1093 A1101 44 Obsolete. McQuay logo; part no. 02005935; °F/°C scaleplate. 51, 53 Carrier logo; part no. HH07AT174; used with Q674B. T874A1036 Replacement has °F/°C scaleplate. Y594C1421 or When using the T874C1036, T874A1036a set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. A1119 82 Obsolete. Sears logo; part no. 541. 91441/49. 9144; °F/ °C scaleplate; used with Q674E1007; used in Y594A1068. T874A1036 Replacement has °F scaleplate. A1127 44 Obsolete. Climate Control logo; part no. 02005936; °C scaleplate. T874A1036 Replacement has °F scaleplate. A1135 44 Fedders multi-logo; part no. THTX-110-WCHA, 88-58-00500-001. T874A1036 A1143 44 Honeywell logo; °C scaleplate. T874A1036 A1150 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; field adjustable locking levers (68°F max. heat, 78°F min. cool). T874A1150 A1168 44 Obsolete. Trane Comfort Corps logo. T874A1036 A1176 44 Honeywell logo; meets DoD specs; includes Allen wrench and screws to lock cover; no thermometer; nonadjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers. T874A1176 A1184 A1192 a Trade Model Replacement Description 51, 53 Trane logo; part no. BAY28X182; °F/°C scaleplate; automatic fan in heating and cooling modes; heat anticipator set at 0.4A; used with Q674B1141, E1080. 44 Obsolete. Lennox logo; part no. 13F0001; °C scaleplate; heat anticipator factory set at .458A. Both the thermostat and subbase must be replaced. 60-2485—8 46 Replacement has °F scaleplate. T874A1036a When used with Q674E1080, set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary; replacement has °F scaleplate. T874A1036 Replacement has °F scaleplate. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number A1200 Fig. No. Trade Model Replacement Description 51, 53 Obsolete. Carrier logo; part no. HH07AT164; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674B. T874A1036 a Remarks Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary; replacement has °F scaleplate. A1226 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover. T874A1036 A1234 44 Obsolete. Friedrich Climate Master logo; heat anticipator factory set 1.2A. T874A1036 A1242 44 Obsolete. Friedrich Climate Master logo. T874A1036 A1259 44 Obsolete. Wesco logo; heat anticipator set at 0.8A. T874A1036 A1267 59 Obsolete. McQuay logo; used with Q674Q1004. T874A1036 A1275 44 Obsolete. Lennox logo; part no. 13F0101; meets DoD specifications. T874A1176 A1283 75 McQuay Air Conditioning logo; part no. 03005047; used with Q674C1132 and thermistor to display outdoor temperature. T874A1036 Replacement does not have ability to display external temperature or momentary system switch position. A1291 64 No logo; three-speed fan; one setpoint lever for heat and cool setpoints; used with Q674Q1012; used in Y594A1126. T874A1036/ Q674B1075a Replacement has two levers and 1 speed fan. A1309 44 Obsolete. Arcoaire Air Conditioning and Heating logo; part no. AO2076; includes Allen wrench and screws to lock cover. T874A1036 A1317 44 Obsolete. McQuay logo; part no. 60685301; no scaleplate; used with Q674A-E,G. T874A1036 A1325 75 Obsolete. McQuay logo; part no. 60685401; no scaleplate; used with Q674C1306 and outdoor thermistor to display outdoor temperature. T874A1036 A1341 44 Obsolete. Trane logo; part no. THT-0577; meets DoD specifications. T874A1176 A1358 44 York-Miraco logo. T874A1036 A1366 51, 53 Obsolete. BDP Multi-logo; part no. HH07AT182. T874A1036a Replacement has °F scaleplate. Replacement does not have ability to display external temperature or momentary system switch position. Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. A1374 44 American Standard logo; part no. ASYSTAT610; heat anticipator factory set at 0.4A. T874A1036a A1390 44 Obsolete. Climate Control logo; part no. 654958804; °F/ °C scaleplate. T874A1036 Replacement has °F scaleplate. A1416 44 Obsolete. Reznor logo; part no. 654758803; °F/°C scaleplate. T874A1036 Replacement has °F scaleplate. A1424 214 Obsolete. Carrier Olympia Series Split System logo; part no. HH07AT194; used with Q674B1455 (HH93AZ208). A1440 91 Obsolete. Simplex System 2000 logo; heat anticipator factory set at 1.2A; used with Q674G1005; used in Y594A. T874A1036 A1465 212 Honeywell Trol-A-Temp™ logo; Premier White® color; heat anticipator factory set at 0.10A; used with Q674E1379. None aBoth See OEM for replacement. See Trol-A-Temp for replacement. the thermostat and subbase must be replaced. 47 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. A1481 44 Obsolete. Honeywell logo; Carrier part no. HH621602; includes locking cover and non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool). T874A1036 A1507 44 Obsolete. Climate-Tel logo; includes Allen wrench and screws to lock cover and non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool). T874A1176 A1523 224, 225 Obsolete. AAF/Snyder General logo; part no. 066804404; °F/°C scaleplate; no cooling anticipation; used with Q674E1312, C1298. See OEM for replacement. A1549 224, 225 Obsolete. McQuay logo; part no. 066816601; no cooling anticipation; used with Q674E1312, C1298. See OEM for replacement. A1556 Trade Model Replacement Description 51, 53 Carrier logo; part no. HH07AT164-W; °C scaleplate; Premier White® color; includes Allen wrench and screws to lock cover; used with Q674B. T874A1036a A1572 224, 225 Obsolete. McQuay logo; part no. 066816611; Premier White® color; °F/°C scaleplate; no cooling anticipation. See OEM for replacement. A1580 91 California Economizer logo; Premier White® color; heat anticipator factory set at 1.2A. T874A1036 A1598 224, 225 McQuay logo; part no. 073319001; Premier White® color; °F/°C scaleplate; includes Allen wrench, screws to lock cover and AAF insert. See OEM for replacement. A1614 44 Honeywell logo; TRADELINE® model; °C scaleplate; Premier White® color; includes Allen wrench and screws to lock cover; used with Q674B. T874A1036 A1622 44 Obsolete. York logo; part no. 2TH04703224A; includes Allen wrench and screws to lock cover and nonadjustable range stops set at 72°F (max. heat) and 78°F (min. cool). T874A1010 B1001 44 Obsolete. Honeywell logo. T874B1019 B1019 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover. T874B1019 44 Obsolete. Westinghouse logo. T874B1019 T874B B1027 B1035 Remarks Replacement has °F scaleplate; replacement is beige. Replacement has °F scaleplate; replacement is beige. 1-stage heat, 2-stage cool. 44, 46 Obsolete. Trane logo; used with Q674B1018, B1075; used in Y594B1026, B1034. T874B1019 B1043 44 Obsolete. Honeywell logo; °C scaleplate. T874B1019 Replacement has °F scaleplate. B1050 44 Lennox logo; part no. 13F0201; °F/°C scaleplate. T874B1019 Replacement has °F scaleplate. B1068 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover. T874B1019 Replacement has °F scaleplate. B1076 88 Obsolete. Lennox Power Saver Two-Speed logo; part no. 91C7401; °F/°C scaleplate; used with Q674E1155. T874B1019 Replacement has °F scaleplate. B1084 44 Obsolete. Lennox Two-Speed logo; part no. 13F0301; °C scaleplate. T874B1019 Replacement has °F scaleplate. B1092 44 Obsolete. Honeywell logo; Heil Quaker part no. HQ521389HW. T874B1019 B1100 88 Obsolete. Janitrol logo; part no. CHTS36-60; °F/°C scaleplate; used with Q674E1338; used in Y594B1042. T874B1019 Replacement has °F scaleplate. B1118 44 Honeywell logo; °C scaleplate; used with Q674A-E, G. T874B1019 Replacement has °F scaleplate. aBoth the thermostat and subbase must be replaced. 60-2485—8 48 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. B1134 222 T874C Obsolete. Carrier Synergy 2000 logo; part no. HH07AT199; °C scaleplate; used with Q674E1395 (HH93AZ209). T874B1019/ Q674E1049a Remarks Wiring differences (old=new): W1=W; RC-RH jumper required; replacement has no LEDs. 2-stage heat, 1-stage cool. C1000 44, 76 Honeywell logo; used with Q674B1075, C1181; used in Y594C1058. T874C1018 C1018 60, 61, Honeywell logo; TRADELINE model; includes Allen 81, 92 wrench and screws to lock cover; used with Q674C1074. T874C1018 C1026 44 Obsolete. AAF logo; °C scaleplate; includes Allen wrench and screws to lock cover; non-adjustable range stops set at 23°C (max. heat and min. cool) (73°F). T874C1018 Replacement has °F scaleplate. C1034 44 Lennox logo; part no. 13F0401; °F/°C scaleplate. T874C1018 Replacement has °F scaleplate. C1042 44 Obsolete. Westinghouse logo; H1 anticipator factory set at.75A; H2 anticipator factory set at 1.2A; used with Q674A-E,G. T874C1018 C1059 C1067 C1075 44, 142 Obsolete. Amana Air Conditioning logo; part no. D68535-2; H1 anticipator factory set at 1.2A; used with Q674E1056, Q674B1059, Q674F1022; used in Y594C1009, Y594C1017, Y594C1256, Y594C1330. 44 Obsolete. Sears logo; part no. 42. 9297; °F/°C scaleplate. 51, 53 Carrier logo; part no. HH07AT170; used with Q674B1166. T874C1018 T874C1018 44 Obsolete. Trane logo; used with Q674E1007; used in Y594C1082. T874C1018 C1117 44 Honeywell logo; °C scaleplate. T874C1018 60, 61, Obsolete. Honeywell logo; 12°F (6.7°C) differential 92 between stage 1 heat and stage 2 heat; used with Q674G1047. 96 Obsolete. AAF/Snyder General logo; part no. 4ELN7546; no H1 heat anticipation; used with Q674AG,N and Q674C1173. T874C1018 C1141 44 Obsolete. Honeywell logo; meets DoD specs; includes Allen wrench and screws to lock cover; no thermometer; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers. T874C1141 C1158 44 Obsolete. Solaron special. T874C1018 51, 53 Obsolete. Carrier logo; part no. HH07AT160; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674B. Replacement has °F scaleplate. T8611M2025 C1133 C1166 Replacement has °F scaleplate. Y594C1421 or When using the T874C1018, T874C1018a set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. C1083 C1125 a Trade Model Replacement Description T874C1018a C1174 44 Obsolete. Goettl logo. T874C1018 C1182 60 Obsolete. Goettl logo; H1 anticipator factory set at 0.8A; used with Q674N1015. T874C1018 C1190 44 Obsolete. Lennox logo; part no. 13F0501; °C scaleplate. T874C1018 Must have H1 anticipator set to maximum value. Replacement has °F scaleplate; set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Replacement has °F scaleplate. Both the thermostat and subbase must be replaced. 49 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Trade Model Replacement Description Remarks C1216 44 Obsolete. Fasco part no. 1230-8197. T874C1018 C1224 105 Obsolete. Square D logo. T874C1018 C1240 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover. T874C1018 Replacement has °F scaleplate. C1257 44 Obsolete. Singer part no. 0200-5931; 8°F (4.4°C) differential between H1 and H2 heat. T874C1125 Replacement has 12°F differential between H1 and H2 heat. C1265 44 Obsolete. Singer special; °C scaleplate; 5°C (8°F) differential between H1 and H2 heat. T874C1125 Replacement has 12°F differential between H1 and H2 heat; replacement has °F scaleplate. C1273 44 Honeywell logo; °C scaleplate; includes Allen wrench and screws to lock cover; non-adjustable range stops factory set at 23°C (max. heat and min. cool) (73°F). T874C1018 Replacement has °F scaleplate. C1281 44 Obsolete. Heat Wave special. T874C1018 C1307 44 Obsolete. Friedrich Climate Master logo. T874C1018 C1315 44 Obsolete. Wesco logo; heat anticipator factory set at 0.8A. T874C1018 C1323 44 Obsolete. Le Chauffage Urbain special; °C scaleplate. T874C1018 82, 141 Obsolete. Duotherm logo; used with Q674E or Q674F. T874C1018 C1331 a Fig. No. Replacement has °F scaleplate. C1349 61 Obsolete. Sigler logo; used with Q674N1023. T874C1018 C1372 52 Obsolete. Honeywell logo; used with Q674B1190. T874C1018/ Q674B1034 For systems requiring automatic fan in cooling mode only. T874C1018/ Q674B1075 For systems requiring automatic fan in heating and cooling. C1398 105 Obsolete. Fedders logo; °F/°C scaleplate; used with Q674L1090. Y594R1425a Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate. C1406 105 Obsolete. Climatrol logo; °F/°C scaleplate; used with Q674L1090. Y594R1425a Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate. C1414 105 Obsolete. Airtemp logo; °F/°C scaleplate; used with Q674L1090. Y594R1425a Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate. C1422 187 Obsolete. Honeywell logo; used with Q674B1208. C1430 49 Obsolete. Lennox Zone Master Two-Speed logo; part no. 25F7201; used with Q674B1224. T874C1018 C1448 110, 190 Obsolete. Lennox logo; part no. 24F5101; meets DoD specifications; requires outdoor reset; used with Q674L1165, L1355. Y594R1763a C1455 127 Obsolete. Williamson logo; used with Q674L1322. Y594R1243a C1463 82 Obsolete. AAF logo; °C scaleplate. T874C1018 C1471 56 Obsolete. Mammoth logo; part no. 71120102; used with Q674B1257; used in Y594C1314. T874C1018 Both the thermostat and subbase must be replaced. 60-2485—8 50 None Wiring differences (new=old): R=V-VR, Y=M, G=F, B-X, W=Y, T=A, O=R, X2=E; Emergency Heat becomes stage 1 heat source. Replacement has °F scaleplate. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. C1489 121 Obsolete. Honeywell logo; non-adjustable range stops set at 75°F (max. heat and min. cool) (24°C); used with Q674L1157. Y594C1322 C1497 121 Obsolete. Honeywell logo; meets DoD specifications; used with Q674L1157. Y594C1322a C1513 44 Obsolete. Borg-Warner multi-logo; part no. 6TH11703124A. T874C1018 C1562 44 Obsolete. Honeywell logo; Heil Quaker part no. HQ712001HW. T874C1018 C1570 45 Obsolete. Williamson logo; used with Q674B1000; used in Y594C1280. T874C1018 C1638 121 Obsolete. Honeywell logo; meets DoD specifications; includes Allen wrench and screws to lock cover; no thermometer; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers; used with Q674L1561; used in Y594C1322. Y594C1322a C1653 70 Obsolete. Fiberglas Canada; °C scaleplate; no H1, H2, or C1 anticipation; used with Q674S1000; used in Y594C1348. See OEM for replacement. C1661 99 Obsolete. McQuay logo; part no. 61202401; °F/°C scaleplate; includes momentary system switch position with spring release; used with Q674C1363. T874C1125/ Q674B1075a C1695 45 Obsolete. Miller logo; used with Q674B1000; used in Y594C1355. T874C1018 C1703 45 Obsolete. Intertherm logo; used with Q674B1000; used in Y594C1363. T874C1018 C1737 44 Obsolete. Honeywell logo; Carrier part no. HH621603. T874C1018 C1745 44 Obsolete. AAF/Snyder General logo; part no. 4ELN7919. T874C1018 C1752 219 Obsolete. McQuay/Snyder General logo; part no. 061202402; 12°F offset between H1 and H2; °F/°C scaleplate; no C1 anticipation; used with Q674C1363. T8611M2025 C1760 44 Bard logo. T874C1018 C1778 219 Obsolete. AAF/Snyder General logo; part no. 066804405; 12°F offset between H1 and H2; °F/°C scaleplate; no C1 anticipation; used with Q674C1363. See OEM for replacement. C1794 53 Obsolete. Carrier logo; Canada; part no. HH07AT160-W; Premier White® color; °C scaleplate; includes locking cover. T874C1018 C1802 246 Obsolete. California Economizer logo; °F/°C scaleplate; used with Q674G1005; used in Y594C1371. T874C1018 C1810 237 Obsolete. Honeywell logo; TRADELINE model; Premier White® color; used with Q674B1547; used in Y594C1389. Y594C1389 C1844 238 Energy Night logo; used with Q674F1592; used in Y594C1413. Y594R1425 C1851 60 Obsolete. Whalen logo. T874C1018 C1869 219 McQuay logo; part no. 0073318801 Premier White® color; °F/°C scaleplate. See OEM for replacement. aBoth Trade Model Replacement Description Remarks a Replacement has HEAT-OFFCOOL system switching; no momentary system switch position; no LEDs. Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Jumper E-W2; system switch: EM.HT.-HEAT-OFF-COOL. the thermostat and subbase must be replaced. 51 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. C1877 53 T874D Trade Model Replacement Description Obsolete. Honeywell logo; TRADELINE model; used with Q674B1554; used in Y594C1421. Y594D1347 166, 82 Obsolete. Honeywell logo; used with Q674F1337, E1007; used in Y594D1222, D1339. T874D1165 D1017 44, 88 Obsolete. Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; used with Q674A-G and Q674E1155. T874D1165 D1025 44 Obsolete. Westinghouse logo; H1 anticipator factory set at 0.75A; H2 anticipator factory set at 1.2A. T874D1165 D1033 44 Lennox logo; part no. 13F0601; °F/°C scaleplate. T874D1165 D1041 53 York logo; part no. 2TH04701524A; used with Q674B1125. T874D1165 D1058 44 Obsolete. Shiger special. T874D1165 44 Obsolete. ITT logo. Replacement has °F scaleplate. T874D1165 D1074 51, 53, Carrier logo; part no. HH07AT172; used with 146 Q674F1030 (HH93AZ174), F1063 (HH93AZ181) or Q674B. T874D1165a D1082 44, 46, Trane logo; used with Q674B1018, C1009, B1075, 48, 72 B1133; used in Y594D1024, D1040. T874D1165 D1090 44 Obsolete. Dunham-Bush logo. T874D1165 D1108 44 Obsolete. Westinghouse logo. T874D1165 D1116 Jumper RC-RH; system switch: OFF-HEAT-AUTOCOOL 2-stage heat, 2-stage cool. D1009 D1066 Remarks 76, 89, Obsolete. Comfortmaker logo; part no. 1505-682; °F/°C 94 scaleplate; used with Q674C1116, E1197, G1104. T874D1165 Set H1 anticipator for current draw of fan and stage 1 heat primary. Replacement has °F scaleplate. D1124 44 Obsolete. Airtemp special. T874D1165 D1132 44 Honeywell logo; °C scaleplate. T874D1165 Replacement has °F scaleplate. D1140 44 Obsolete. Solaron special. T874D1165 Replacement has °F scaleplate. T874D1165a Replacement has °F scaleplate; set H1 anticipator for current draw of fan and stage 1 heat primary. D1157 D1165 51, 53, Carrier logo; part no. HH07AT172; °C scaleplate; used 146 with Q674B or Q674F1030, F1063. 82 Honeywell logo; SUPER TRADELINE® model; includes Allen wrench and screws to lock cover, field-adjustable range stops, field-adjustable locking levers. T874D1165 D1173 51, 53 Trane logo; part no. BAY28X183; heat anticipator factory set at 0.4A. T874D1165a Set H1 anticipator for current draw of fan and stage 1 heat primary. D1181 51, 53 Obsolete. General Electric logo; locking cover includes Allen wrench and screws to lock cover and range stops set at 72°F (max. heat) and 78°F (min. cool). T874D1165a Set H1 anticipator for current draw of fan and stage 1 heat primary. T874D1165 Replacement has °F scaleplate. D1199 44 Obsolete. Lennox logo; part no. 13F0701; °C scaleplate. D1207 114 Obsolete. Lennox logo; part no. 24F5201; used with Q674L1199 and C815A1013 or Q674L1389. aBoth the thermostat and subbase must be replaced. 60-2485—8 52 T8611M2025 Wiring differences (old=new): (programmable) V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. D1215 44 Obsolete. Friedrich Climate Master logo; part no. AT5415; °F/°C scaleplate. T874D1165 Replacement has °F scaleplate. D1223 44 Honeywell logo; Honeywell Canada TRADELINE model; Celsius scale. T874D1165 Replacement has °F scaleplate. D1231 44 Obsolete. Honeywell logo; 12°F (7°C) differential between H1 and H2. T874D1165 Replacement has 2°F differential between H1 and H2. D1249 44 Obsolete. Fedders special. T874D1165 D1256 44 Obsolete. Climatrol special. D1264 107 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT173; used with Q674L1116 (HH93AZ171). D1272 D1280 Trade Model Replacement Description T874D1165 51, 53 Obsolete. Carrier logo; part no. HH07AT162-03; °C scaleplate; used with Q674B. 44 Remarks Obsolete. Command-Aire logo. See OEM for replacement. T874D1165a Replacement thermostat has °F scaleplate; set H1 anticipator for current draw of fan and stage 1 heat primary. T874D1165 D1298 90, 232 Obsolete. Singer special; °C scaleplate; controls two separate heat/cool circuits; used with Q674D or Q674G1054, G1062. See OEM for replacement. D1306 90, 186 Obsolete. Trane special; part no. 02005949; controls two separate heat/cool circuits; used with Q674G1013. See OEM for replacement. D1314 44 Obsolete. McQuay logo; part no. 02005941; 12°F (6.6°C) differential between H1 and H2. T874D1165 D1322 46 Obsolete. Amana logo; part no. D68535-03; used with Q674B1075; used in Y594D1149. T874D1165 D1330 44 Obsolete. Trane logo; part no. 13080242; °C scaleplate. T874D1165 Replacement has °F scaleplate. D1355 44 Obsolete. Climate Control special; part no. 02005942; °C scaleplate; 6°C (11°F) differential between H1 and H2. T874D1165 Replacement has 2°F differential between H1 and H2. D1363 44 Obsolete. McQuay logo; part no. 02005943; 12°F (6.6°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2. T874D1165 Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2. D1405 44 Obsolete. Trane logo; part no. 02005952; 12°F (6.6°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2. T874D1165 Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2. D1413 44 Obsolete. Trane logo; part no. 02005956; 12°F (6.6°C) differential between H1 and H2. T874D1165 Replacement has 2°F differential between H1 and H2. D1421 44 Obsolete. Climate Control special; part no. 02005938; °C scaleplate. T874D1165 Replacement has °F scaleplate. D1439 90 McQuay logo; part no. 02005935; used with Q674G1096. T874D1165 D1447 90 Obsolete. Climate Control special; part no. 02005940; °C scaleplate; used with Q674G1096. T874D1165 Replacement has °F scaleplate. T874D1165a Set H1 anticipator for current draw of fan and stage 1 heat primary. D1454 D1462 aBoth 51, 53 Obsolete. Carrier logo. 80 Obsolete. Fedders multi-logo; part no. THTX-220-A0HB, 88-58-00550-001; used with Q674E1205. Replacement has °F scaleplate; 2°F differential between H1 and H2. T874D1165 the thermostat and subbase must be replaced. 53 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. a Model Number Fig. No. Trade Model Replacement D1470 44 Obsolete. York logo; part no. 2TH04701624A; includes Allen wrench and screws to lock cover; °C scaleplate. T874D1165 Description D1488 44 Obsolete. Risco special. T874D1165 D1496 44 Obsolete. Borg Warner multi-logo; part no. 6TH04701524A; includes Allen wrench and screws to lock cover. T874D1165 D1504 82 York logo; part no. 025-23321-000; °C scaleplate; used with Q674E1007; used in Y594D1180. T874D1165 D1512 44 Honeywell logo; Heil Quaker part no. HQ712002HW. T874D1165 D1520 44 Obsolete. Bard logo; adjustable lever stops set 68°F (max. heat) and 78°F (min. cool). T874D1165 D1538 44 Obsolete. McQuay logo; part no. 02005937. T874D1165 D1553 44 Obsolete. Climate Control special; part no. 02005944; °C scaleplate; 6°C differential between H1 and H2; 3°C differential between C1 and C2. T874D1165 D1561 44 Obsolete. General Electric logo; used with Q674 A-G. T874D1165 D1587 44 Obsolete. Stiles Four Seasons logo. T874D1165 D1595 139 Obsolete. Nepco logo; used with Q674F1394. T874D1165/ Q674B1018a Remarks Replacement has °F scaleplate. Replacement has °F scaleplate. Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2; replacement has °F scaleplate. Replacement has HEAT-OFFCOOL system switching; no LEDs. D1603 44 Obsolete. Arcoaire logo. T874D1165 D1611 44 Obsolete. No logo; Friedrich part no. AT5411; °F/°C scaleplate. T874D1165 Replacement has °F scaleplate. D1629 82 Obsolete. Reznor logo; °F/°C scaleplate; used with Q674E1007; used in Y594D1248. T874D1165 Replacement has °F scaleplate. D1678 44 Obsolete. Honeywell logo; Saudi Oger special; °C scaleplate; one setpoint lever; used with Q674A-K. T874D1165 Replacement has °F scaleplate; separate heating and cooling setpoint levers. D1686 98 Obsolete. McQuay logo; part no. 60685501; 8°F (4.4°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2; used with Q674E1312. T874D1165 Replacement has 2°F differential between H1 and H2; 2°F differential between C1 and C2. D1694 202 Obsolete. McQuay logo; part no. 60685201; used with Q674G1120. See OEM for replacement. D1702 44 Obsolete. McQuay logo; part no. 60685101. T874D1165 D1710 44 Trane logo. T874D1165 D1728 44 York-Miraco logo. T874D1165 D1744 44 American Standard logo; heat anticipator factory set at 0.4A. T874D1165 D1751 44 Obsolete. Goettl logo; part no. 372080; range stops set at 68°F (max. heating) and 78°F (min. cooling). T874D1165 D1769 82 Obsolete. Arcoaire logo; part no. 1506753; °F/°C scaleplate; used with Q674E1346; used in Y594D1297. T874D1165 Replacement has °F scaleplate. D1777 44 Obsolete. Climate Control logo; part no. 65495806; °F/ °C scaleplate. T874D1165 Replacement has °F scaleplate. D1785 82 Obsolete. Comfortmaker logo; part no. 1505753; °F/°C scaleplate; used with Q674E1346; used in Y594D1305. T874D1165 Replacement has °F scaleplate. D1793 44 Obsolete. McQuay logo; part no. 65495805; °F/°C scaleplate. T874D1165 Replacement has °F scaleplate. Both the thermostat and subbase must be replaced. 60-2485—8 54 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number D1801 D1819 D1827 Fig. No. Trade Model Replacement Description 45, 208 Trol-A-Temp by Honeywell logo; H1 and H2 anticipators set at 0.10A; used with Q674B1463, D1115. 44 Marv Air Com Stat logo; part no. 50059; adjustable interstage between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field adjustable range stops; °F/°C scaleplate. 45, 208 Trol-A-Temp by Honeywell logo; Premier White® color; H1 and H2 heat anticipators set at 0.10A; used with Q674B1471, D1123. None T874D1165 None Remarks See Trol-A-Temp for replacement. Replacement has a 2°F fixed interstage differential between H1 and H2 and between C1 and C2; replacement has °F scaleplate. See Trol-A-Temp. D1843 45 Obsolete. Janitrol logo; Goodman part no. CHT 90-120; used with Q674B1000; used in Y594D1321. T874D1165 D1850 44 Honeywell logo; Carrier part no. HH621606. T874D1165 D1868 44 Bard logo; part no. 8405-031; H1 and H2 heat anticipators factory set at 0.25A; 5°F interstage differential between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field adjustable range stops. T874D1165 Replacement has 2°F fixed interstage differential between H1 and H2 and between C1 and C2. D1876 44 Obsolete. AAF/Snyder General logo; part no. 4ELN6981A; °F/°C scaleplate. T874D1165 Replacement has °F scaleplate. Obsolete. Climate-Tel logo. T874D1165 D1892 44 D1918 224, 225 Obsolete. AAF/Snyder General logo; °F/°C scaleplate; no cooling anticipation; used with Q674E1312, C1298; 66804407. See OEM for replacement. D1926 226 Obsolete. AAF/Snyder General logo; °F/°C scaleplate; no cooling anticipation; used with Q674G1120; 66804406. See OEM for replacement. D1934 44 Bard logo. T874D1165 D1942 82 Honeywell logo; TRADELINE model; used with Q674E1403; used in Y594D1347; designed to replace York part no. 2TH04701024. Y594D1347a D1959 44 Rheem part no. 41-21444-01. T874D1165 D1967 44 Obsolete. Desert Aire logo. D1975 224, 225 Obsolete. McQuay part no. 066816603; °F/°C scaleplate; no cooling anticipation. See OEM for replacement. D1983 226 Obsolete. McQuay part no. 066816602; °F/°C scaleplate; no cooling anticipation; used with Q674G1120. See OEM for replacement. D1991 T874D1165 51, 53 Carrier logo; Premier White® color; °C scaleplate. T874D1165a D2007 44 Ultra-Zone logo. T874D1165 D2023 44 Honeywell logo; TRADELINE model; Premier White® color; °C scaleplate; includes locking cover; used with Q674A-K. T874D1165 D2031 82 Obsolete. Honeywell logo; no cover; used with Q674E1049 and TG504A1025; used in Y594D1354. D2049 aBoth 45, 72, Obsolete. Carrier Heat Pump System Control logo; part 55, 66, no. HH07AT236; °F/°C scaleplate; used with Q674B-D, 184 Q674G; used in Y594D. Set H1 anticipator for total current draw of fan and stage 1 primary; replacement has °F scaleplate. Replacement has °F scaleplate and is beige. T874D1165 or Y594D1354 T874D1165 Replacement has °F scaleplate. the thermostat and subbase must be replaced. 55 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. D2056 44 Obsolete. ComStat logo; part no. 50056; °F/°C scaleplate; adjustable interstage on both heating and cooling; includes locking cover and field-adjustable locking levers. T874D1165 Replacement has °F scaleplate and 2°F fixed differential in heating and cooling. D2064 53 Obsolete. Carrier Weathermaker; part no. HH07AT209; stage 1 and 2 heat anticipator factory set 0.1A; taupe color; used with Q674E1445; used in Y594D1412. T874D1165 Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Replacement is beige. D2072 53 Obsolete. Carrier Zone Perfect; part no. HH07AT208; taupe color; used with Q674E1445; used in Y594D1420. T874D1165 Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary. Replacement is beige. D2080 139 Obsolete. Hydroheat logo. T874D1165/ Q674B1018a Replacement system switch: HEAT-OFF-COOL; no LEDs. D2098 44 Obsolete. Honeywell logo; °F scaleplate; one setpoint lever; used with Q674D1008; used in Y594D1438. T874D1165 Replacement has °F scaleplate and two setpoint levers D2106 44 Obsolete. Honeywell logo; °C scaleplate; one setpoint lever; used with Q674D1008; used in Y594D1446. T874D1165 Replacement has °F scaleplate and two setpoint levers. D2114 44 Obsolete. Bard logo; °C scaleplate. T874D1165 Replacement has °F scaleplate. D2122 224, 225 Obsolete. McQuay T874D2023 Replacement has °C scaleplate. T874D1165 Replacement has °F scaleplate. D2130 226 Obsolete. McQuay D2148 44 Obsolete. Dry Aire Systems logo; °F/°C scaleplate. T874D1165 139 Hydroheat logo; Premier White® color; °F/°C scaleplate; used with Q674F1634. T874D1165/ Q674B1018a D2163 208 Obsolete. Amana logo; part no. P1217501F; °F/°C scaleplate. T874D1165 D2171 44 Obsolete. Amana logo; part no. P1217701F; °F/°C scaleplate. T874D1942 D2189 44 Armstrong logo; part no. 01142A024; °F/°C scaleplate; includes Air Ease insert. T874D1165 D2197 44 Liebert logo; part no. 138968P3; °F/°C scaleplate; interstage differential between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field-adjustable locking levers. T874D1165 D2205 44 Aaon logo; Premier White® color; °F/°C scaleplate. T874D1165 Replacement system switch: HEAT-OFF-COOL; no LEDs. 0-stage heat, 2-stage cool. E1008 44 Obsolete. Honeywell logo. T874E1016 E1016 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; field-adjustable locking levers. T874E1016 E1024 44 Obsolete. Westinghouse logo. T874E1016 E1032 44 Lennox logo; part no. 13F0901; °F/°C scaleplate. T874E1016 E1040 72 Obsolete. Trane logo; used with Q674C1009; used in Y594E1015. T874E1016 Both the thermostat and subbase must be replaced. 60-2485—8 Remarks See OEM for replacement. D2155 T874E a Trade Model Replacement Description 56 Replacement has °F scaleplate. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. E1081 44 Trane logo; part no. BAY28X186; °F/°C scaleplate. T874E1016 Replacement has °F scaleplate. E1099 44 Obsolete. Lennox logo; part no. 13F1001; °C scaleplate. T874E1016 Replacement has °F scaleplate. E1107 44 Honeywell logo; °C scaleplate. T874E1016 Replacement has °F scaleplate. E1123 44 Obsolete. Amana logo; part no. D68535-4. T874E1016 E1149 44 Obsolete. York logo; part no. 2TH04701724A. T874E1016 E1156 44 Obsolete. Borg Warner multi-logo; part no. 6TH04701724A. T874E1016 E1164 44 Obsolete. E. A. Juffali & Bros. logo. T874E1016 E1206 44 Obsolete. Trane logo. T874E1016 E1230 44 Obsolete. Climar logo. T874E1016 T874F Remarks 2-stage heat, 0-stage cool. F1007 44 Honeywell logo. T874F1015 F1015 44 Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; field-adjustable locking levers. T874F1015 F1023 44 Obsolete. Lennox logo; part no. 13F1101. T874F1015 F1031 44 Obsolete. Honeywell logo; °C scaleplate; used with 40003440-001 wallplate; used in Y594F1022. T874F1015 Replacement has °F scaleplate. F1049 44 Obsolete. Lennox logo; °C scaleplate. T874F1015 Replacement has °F scaleplate. F1056 55, 66 Obsolete. Honeywell logo; stages 1 and 2 heat electrically isolated; used with Q674D1008. F1072 44 Obsolete. Wesco logo; heat anticipator factory set at 0.8A. T874F1015 F1098 189 Obsolete. Lennox logo; used with Q674D1008 to control an M839. T874F1015 F1106 95 Obsolete. Oneida logo; part no. 30A0287-02; used with Q674K1018 on combination wood and oil applications. T874F1155 F1114 44 Honeywell logo; Honeywell Canada TRADELINE model; °C scaleplate; includes Allen wrench and screws to lock cover; field-adjustable locking levers. T874F1015 Replacement has °F scaleplate. F1122 62 Obsolete. Honeywell logo; two heat setpoint levers; used with Q674B1307. T874F1015/ Q674D1040 Replacement has no LED. T874F1015 Replacement has °F scaleplate. F1130 72, 91 Obsolete. Reznor logo; °F/°C scaleplate; used with Q674C, D, or G; used with Q674C1009, G1005; used in Y594F1048. None F1148 44 Obsolete. Trane logo; part no. THT 0584. T874F1015 F1155 95 Honeywell logo; used with Q674K1026 on combination wood and oil applications. T874F1155 T874G G1006 a Trade Model Replacement Description Set H1 and H2 anticipators to lowest settings. Heat pump models; 2-stage heat, 1-stage cool; 1–stage changeover. 84, 155 Obsolete. Honeywell logo; used with Q674E1015. Y594G1252a Wiring differences (old=new): R=O, M=Y, F=G, V=R, Y=W2; E-W2 jumper required. Both the thermostat and subbase must be replaced. 57 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. Trade Model Replacement Description Remarks G1014 86, 150 Obsolete. Lennox logo; part no. 24F5801; °F/°C scaleplate; H2 anticipator factory set at 0.25A for fast cycle performance; changeover in cooling mode; independent heating and cooling circuits; used with Q674E1148, F1113. Y594G1252 Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R (must use single transformer). G1022 86, 150 Obsolete. Lennox logo; part no. 24F5701; °F/°C scaleplate; H2 anticipator factory set at 0.25A for fast cycle performance; changeover in cooling mode; independent heating and cooling circuits; used with Q674E1148, F1113. Y594G1252a Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R (must use single transformer). Y594G1252a Wiring differences when replacing T874G/Q674J1019 (old=new): W=W2. None See subbase description for replacement information. Y594G1419 Wiring differences (old=new): C=X; jumper Y1-W1. Wiring differences (old=new): A=L. G1048 153, 159 Obsolete. Westinghouse logo; H2 anticipator factory set at 1.2A; used with Q674F1121, J1019. G1055 161 Carrier Heat Pump System Control logo; part no. HH07AT171; H2 anticipator factory set at 0.8A; changeover in cooling mode; used with Q674J1035 (HH93AZ173). G1071 50, 103, Obsolete. Carrier Heat Pump System Control logo; 126, meets DoD specifications; H2 anticipator factory set at 183 0.8A; used with Q674P1005 (HH93AZ169), L1041 (HH93AZ175), B1158, or J1050. a G1089 154 Obsolete. Marvair logo; special for Crispaire; H2 anticipator factory set at 1.2A; used with Q674F1204; used in Y594G1153. Y594G1393a G1097 155 Obsolete. Honeywell logo; Rheem part no. ZXMT-B79; used with Q674F1238 (41-20797-14). Y594G1252a G1105 153 Obsolete. Heat Wave (Southwest Mfg.) logo; H2 anticipator factory set at 1.2A; used with Q674F1170. Y594G1252a G1113 103 Obsolete. Carrier Heat Pump System Control logo; meets DoD specifications; H2 anticipator factory set at 0.8A; used with Q674L1041. Y594G1419a Wiring differences (old=new): C=X; jumper Y1 -W1. G1121 103 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT161; °C scaleplate; H2 anticipator factory set at 0.8A; includes Allen wrench and screws to lock cover. Y594G1419a Wiring differences (old=new): C=X; jumper Y1-W1. G1139 143, 234 Obsolete. Honeywell logo; used with Q674B1240, C1108. None See subbase description for replacement information. G1147 148 Obsolete. Honeywell logo; changeover in cooling mode; used with Q674F1139. Y594G1252a Wiring differences (old=new): C=X. Y594G1252a See subbase description for replacement information. W1-Y1 jumper required. G1154 84, 139 Obsolete. Lennox logo; used with Q674E1015, F1105. G1162 155 Obsolete. Lennox logo; meets DoD specifications; used with Q674F. Y594G1419a G1170 160 Obsolete. York logo; part no. 2TH11702424A; H2 anticipator is fixed; used with Q674J1027; used in Y594G1013. Y594G1567a G1188 147 Obsolete. Honeywell logo; Keeprite/Westinghouse special; H2 anticipator factory set 1.2A; °C scaleplate; changeover in cooling mode; used with Q674F1295. Y594G1252a G1196 160 Obsolete. York logo; °C scaleplate; changeover in cooling mode; used with Q674J1027; used in Y594G1138. Y594G1567a aBoth the thermostat and subbase must be replaced. 60-2485—8 58 Wiring differences (old=new): S=L. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. G1204 162 Honeywell logo; designed for use on Trane heat pumps; no H2 anticipation; changeover in cooling mode; used with Q674J1043 and C815A1005; used in Y594G1161. Y594G1161 G1212 155 Obsolete. Honeywell logo; H2 anticipator factory set at 0.2A; changeover in cooling mode; includes shunt to bypass H2 anticipator with W3 heat relays; used with Q674F1238. Y594G1252a G1220 235 Obsolete. Rheem logo; part no. RXMT-C71; changeover in cooling mode; used with Q674F1238. Y594G1252a G1238 155 Obsolete. Ruud logo; part no. UXMT-C71; changeover in cooling mode; used with Q674F1238. Y594G1252a G1246 Trade Model Replacement Description a Remarks Designed for use on Trane heat pumps. Obsolete. Honeywell logo; changeover in cooling mode. 155 Used with Q674F1212; used in Y594G1195, G1252, G1369. Y594G1252a 170 Used with Q674F1410; used in Y594G1393. Y594G1393a G1261 58, 157 Obsolete. Borg-Warner; used with Q674D1032, F1253. None See subbase description for replacement information. G1279 58, 157 Obsolete. Bryant logo; used with Q674D1032, F1253. None See subbase description for replacement information. G1287 58, 157 Obsolete. Wesco logo; used with Q674D1032, F1253. None See subbase description for replacement information. Wiring differences (old=new): Y=Y2, O=Y1, W=W2; jumper W1-Y2. G1295 58 Obsolete. York logo; part no. 2TH11702724A; used with Q674D1032. T874D1165/ Q674D1040 G1345 160 Obsolete. York logo; part no. 2TH11702624A; °C scaleplate; used with Q674J1027. Y594G1575a G1352 73 Obsolete. Command-Aire logo; 12°F differential between H1 and H2 for night setback; used with Q674C1066. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D1004 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=RH; RC-RH jumper required; includes night setback. G1378 79 Obsolete. Mammoth logo; H2 anticipator factory set at 0.8A; 12°F differential between H1 and H2 for night setback; °F/°C scaleplate; used with Q674C1124; used in Y594G1294. Y594H1012a Wiring differences (old=new): R1=none, R2=L; R-L jumper required; no night setback. T8090A1007/ Includes night setback; W-Y Q682A1038a jumper required. (programmable) G1402 129 Obsolete. York part no. 2TH11702824A; meets DoD specifications; used with Q674L1363. G1410 155 Obsolete. Borg-Warner multi-logo; part no. 6TH11703024A; used with Q674F1311. G1428 160 Obsolete. Borg-Warner multi-logo; part no. 6TH11702424A; used with Q674J1027; used in Y594G1229. Y594G1567a G1436 58 Obsolete. Borg-Warner multi-logo; part no. 6TH11702724A. T874D1165/ Q674D1040 aBoth Y594R1425a Wiring differences (old=new): W=W2, X=E, B=X; jumper Y-W1. T874G1246a or Y594G1252a Wiring differences (old=new): Y=Y2, O=Y1, W=W2; jumper W1-Y2. the thermostat and subbase must be replaced. 59 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. Trade Model Replacement G1444 160 Obsolete. ROCA logo; °C scaleplate; used with Q674J1027. G1451 155 Obsolete. BDP multi-logo; part no. HH641502; used with T874G1246a or Q674F1212; used in Y594G1245. V594G1252a G1469 194 Obsolete. No logo; Addison special; used with Q674F1345; used in Y594G1344. G1485 163 Obsolete. AAF logo; part no. 4ELN-7839; °F/°C Y594G1393a scaleplate; 10°F differential between H1 and H2 for night setback and momentary RESET system switch position; T8611G1004 used with Q674C1199. (programmable) Description Y594G1567a Y594G1252a Remarks Replacement has °F scaleplate. Wiring differences (old=new): Y1=O, C=X, W1=Y1, X=L. No night setback or momentary reset switch. Includes night setback; no momentary reset switch. G1493 167 Obsolete. Honeywell logo; Rheem part no. 41-20797-18; used with Q674F1360. Y594G1526a G1501 195 Obsolete. Coleman logo; part no. 3600-375; changeover in cooling mode; used with Q674F1378. Y594G1252a G1535 163 Obsolete. AAF/Snyder General logo; 4ELN7839 °F/°C Y594G1393a No night setback or scaleplate; 10°F differential between H1 and H2 for night momentary reset switch. setback and momentary RESET system switch position; T8611G1004 Includes night setback. used with Q674C1199. (programmable) G1543 194 Obsolete. Addison logo; Weather King part no. 8403197; used with Q674F1345; used in Y594G1328. Y594G1252a Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L. G1568 160 Obsolete. Luxaire logo; part no. 026-00068-000; °C scaleplate; used with Q674J1126; used in Y594G1351. Y594G1367a Replacement has °F scaleplate. G1576 169 Obsolete. Coleman logo; part no. 3600-373; changeover in heating and cooling mode; used with Q674F1402; used in Y594G1377. Y594G1633a G1584 73 Obsolete. No logo; Friedrich part no. AT5784; 8°F (4.4°C) differential between H1 and H2; used with Q674C1223. Y594H1012a Wiring differences (old=new): L1=L; changeover in cooling only. Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) G1592 155 Obsolete. Arcoaire logo; used with Q674F1212; used in Y594G1385. G1600 199 Obsolete. Honeywell logo; meets DoD specifications; used with Q674F1428; used in Y594G1401. Y594G1419a Wiring differences (old=new): jumper W1-Y1. G1618 73 Obsolete. Honeywell logo; 12°F differential between H1 and H2 for night setback; used with Q674C1256. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; L-R jumper required; no night setback. T874G1246a or Y594G1252a T8600C1162 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; includes night setback. G1626 167 Honeywell logo; used with Q674F1436; used in Y594G1526. None G1642 227 Honeywell logo; TRADELINE model; meets DoD specifications; used with Q674F1444; used in Y594G1419. Y594G1419a aBoth the thermostat and subbase must be replaced. 60-2485—8 60 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. G1659 177 Trade Model Replacement Description Obsolete. Mammoth logo; 0.8A maximum current through B or O terminal; 12°F differential between H1 and H2 for night setback; used with Q674C1330; used in Y594G1427. Y594H1012 a Remarks Wiring differences (old=new): R2=L, R1=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) G1675 174 Obsolete. American Standard logo; part no. ASYSTAT650; used with Q674J1142; used in Y594G1443. Y594G1161a G1691 176 Obsolete. Command Aire logo; part no. P1013-0060; 12°F (6.6°C) differential between H1 and H2 for night setback; used with Q674C1389, C1397. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, R=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) a G1717 175 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT102N; used with Q674J1167; used in Y507J1201. Y594G1252a G1741 227 Honeywell logo; TRADELINE model; includes factory set range stops at 68°F (max. heat) and 78°F (min. cool); Premier White® color; used with Q674F1477; used in Y594G1476. Y594G1476a G1758 211 Trol-A-Temp by Honeywell logo; Premier White® color; changeover is provided by Trol-A-Temp zone panel; used with Q674F1485; used in Y594G1492. None G1774 216 Obsolete. Comfortmaker logo; part no. 1505756; used with Q674J1175; used in Y594G1500. Y594G1252a Wiring differences (old=new): E=W2, W1=W3, X=E, C=X. G1782 216 Obsolete. Arcoaire logo; part no. 1506756; used with Q674J1175; used in Y594G1518. Y594G1252a Wiring differences (old=new): E=W2, W1=W3, X=E, C=X. G1790 161 Obsolete. Carrier logo; Premier White® color; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674J1191. Y594G1252a Wiring differences (old=new): C=X; replacement has °F scaleplate. G1816 163 Climate Master logo; part no. AT5716; °F/°C scaleplate; 10°F differential between H1 and H2 and momentary RESET system switch position. Y594G1393a No momentary reset switch. G1824 227 Honeywell logo; Australian TRADELINE model; Premier White® color; °C scaleplate; used with Q674F1477; used in Y594G1534. Y594G1476a G1832 231 Obsolete. Intertherm logo; used with Q674F1519; used in Y594G1542. Y594G1252a Replacement has auto changeover in cooling mode only. G1840 231 Obsolete. Miller logo; used with Q674F1519; used in Y594G1559. Y594G1252a Replacement has auto changeover in cooling mode only. G1857 229 Obsolete. Lennox logo; °C scaleplate; Premier White® color; used with Q674F1535; used in Y594G1583. Y594G1161a Wiring differences (old=new): E=X2, C=B, L=F. G1865 160 Honeywell logo; TRADELINE model; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424), and York part no. 2TH117704124); used with Q674J1209; used in Y594G1567. Y594G1567a Wiring differences (old=new): C=X, D=L; replacement has AUX. HEAT and EM. HEAT LEDs. See Trol-A-Temp for replacement. Both the thermostat and subbase must be replaced. 61 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. G1873 160 Obsolete. Honeywell logo; TRADELINE model; Premier White® color; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424), and York part no. 2TH117704124); used with Q674J1225; used in Y594G1575. Y594G1567 G1881 167 Rheem; part no. 41-20797-18. Y594G1526a G1899 169 Obsolete. Amana; part no. 10574101; used with Q674F1550; used in Y594G1591. Y594G1633a G1915 155 Econar logo; used with Q674F1212; used in Y594G1609. Y594G1252a 170 Used with Q674F1410. Y594G1393a 176 Trane logo; part no. X13510599010; H2 make 12°F below H1 make. Y594H1012a G1923 Trade Model Replacement Description a Remarks Replacement is beige. Wiring differences (old=new): Y1=O, Y2=Y, R=none; L-R jumper required; no night setback. T8611G1004 Includes night setback. (programmable) G1931 155, 170 G1949 73 Obsolete. Honeywell logo; Premier White® color; °C scaleplate; used with Q674F1568. Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT204; °F/°C scaleplate; H2 make 8°F below H1 make; used in Y594. None Y594H1012a See subbase description for replacement information. Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D1004 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=RH; RC-RH jumper required; includes night setback. G1956 30, 103, Obsolete. Carrier logo; Canada; Premier White® color; 126, °C scaleplate; includes locking cover. 183 Replacement has °F scaleplate. Replacement has °F scaleplate. G1964 160 York logo; Canada; Premier White® color; °C scaleplate; used in Y594G1625. Y594G1575a G1972 169 Honeywell logo; TRADELINE model; used with Q674F1584; used in Y594G1633. Y594G1633a G1980 169 Obsolete. Amana logo; part no. 10574103; used with Q674F1600; used in Y594G1641. Y594G1633a G1998 155 Obsolete. Tempstar logo (Inter-City Products); used in Y594G1658; used with Q674F1212. Y594G1252a G2004 103 Honeywell logo; TRADELINE model; used with Q674L; used in Y594G. Y594G1666 161 Used with Q674J1274; used in Y594G1674. Y594G1674 155, 170 WaterFurnace logo; part no. TA21H03; Premier White® color; °F/°C scaleplate; used with Q674F1667; used in Y594G1716. Y594G1716 G2046 T874H a Y594G1476 Wiring differences (old=new): W3=W2. Heat pump model; 1-stage heat, 1-stage cool, 1-stage changeover in cool. H1005 74 Obsolete. Command Aire logo; used with Q674C1041. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. H1013 74 Obsolete. Friedrich part no. AT5813; °C scaleplate; used with Q674C1041. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required; replacement has °F scaleplate. Both the thermostat and subbase must be replaced. 60-2485—8 62 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. H1021 74 H1039 Remarks Obsolete. Friedrich Climate Master logo; part no. AT5821; °F/°C scaleplate; used with Q674C1041. a Y594H1012 Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required; replacement has °F scaleplate. 79 Obsolete. Mammoth logo; °F/°C scaleplate; used with Q674C1124; used in Y594H1004. Y594H1012a Wiring differences (old=new): R1=R, R2=L. H1054 74 Obsolete. No logo; Friedrich part no. AT5854; used with Q674C1041. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. H1062 164 Honeywell logo; used with Q674C1249; used in Y594H1012. Y594H1012a H1070 172, 173 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT166; °C scaleplate; used with Q674B1406 (HH93AZ200) or Q674C1322 (HH93AZ199). None See subbase description for replacement information. H1088 172, 173 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT167; used with Q674B1406 (HH93AZ200) or Q674C1322 (HH93AZ199). None See subbase description for replacement information. H1096 177 Obsolete. Mammoth Water Source Heat Pump logo; °F/ °C scaleplate; changeover stage 0.8A maximum; used B or O terminal; used with Q674C1330. Y594H1012a Wiring differences (old=new): R1=R, R2=L; L-R jumper required. H1112 74 No logo; Friedrich part no. AT5812; used with Q674C1355. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. H1120 205 Obsolete. Command Aire logo; part no. P1013-0055; used with Q674C1389, C1397. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y. H1138 221 Obsolete. Climate Master logo; part no. AT5838; used with Q674C1470. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; replacement has MALFUNCTION LED only. H1146 205 Trane logo; part no. X13510598010. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y. H1153 173 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT167; °F/°C scaleplate; used with Q674C1322; used in Y594H1053. None See subbase description for replacement information. H1161 74 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT203; °F/°C scaleplate; used with Q674C1496; used in Y594H1038. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. T874J a Trade Model Replacement Description Heat pump model. 2-stage heat, 1-stage cool. J1002 124, 144, 206, 207 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT175; used with Q674J1068 (HH93AZ183), Q674J1159 (HH93AZ196), Q674L1074 (HH93AZ186), Q674L1637 (HH93AZ195). None See subbase description for replacement information. J1010 124, 171 Obsolete. BDP multi logo; part no. 34427DP124/P2722471; used with Q674J1084, L1371. None See subbase description for replacement information. J1028 124, 144, 206, 207 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT165; °C scaleplate; used with Q674J1068 (HH93AZ183), Q674J1159 (HH93AZ196), Q674L1074 (HH93AZ186), Q674L1637 (HH93AZ195). None See subbase description for replacement information. J1036 124, 171 Obsolete. Miller logo; part no. 9132230; used with Q674J1217. T8511G1021 J1044 124, 171 Obsolete. Intertherm logo; part no. 9132240; used with Q674J1217. T8511G1021 J1051 124, 144 Obsolete. Carrier logo; part no. HH07AT165-W; Premier White® color; °C scaleplate. None See subbase description for replacement information. Both the thermostat and subbase must be replaced. 63 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. J1069 124, 144, 206, 207 Obsolete. Honeywell logo; TRADELINE model; used with Q674J1282; used in Y594J1019. T8511G1021 J1077 124, 171 Obsolete. Nordyne logo; part no. 9148300; °F/°C scaleplate. T8511G1021 T874K Remarks Heat pump model; 2-stage heat, 1-stage cool, automatic changeover in heat. K1001 77 Obsolete. LSI Mammoth logo; used with Q674C1090. Y594G1419a Wiring differences (old=new): RH-RC=R, W1=B, W3=W2, W2=W1; remove Y1-W1 jumper. K1019 181 Obsolete. McQuay/Snyder General logo; part no. 60687301; °F/°C scaleplate; H1 anticipator set at 0.83A; 8°F interstage differential between H1 and H2 for night setback; used with Q674C1280. Y594G1252a Wiring differences (old=new): C=X, W=B, A=L; jumper E-W2; no night setback. K1027 181 T874L Obsolete. AAF/Snyder General logo; part no. 066804403; °F/°C scaleplate; H1 anticipator set at 0.83A; 8°F interstage differential between H1 and H2 for night setback; used with Q674C1280. T8611G1004 Wiring differences (old=new): (programmable) C=X, W=B, A=X2; jumper X2R; remove external time clock; includes night setback. Y594G1252a Wiring differences (old=new): C=X, W=B, A=L; jumper E-W2; no night setback. T8611G1004 Wiring differences (old=new): (programmable) C=X, W=B, A=X2; jumper X2-R; remove external time clock; includes night setback. Heat pump model; 2-stage heat, 1-stage cool, changeover in cool. L1000 198 Obsolete. Carrier logo; part no. HH07AT176; used with Q674E1270 (HH93AZ189). Y594G1419a L1018 138, 165 Obsolete. Carrier Multiplex System logo; part no. HH07AT178; used with Q674B1356 (HH93AZ192) or Q674C1264 (HH93AZ193). See OEM for replacement. L1026 198 Obsolete. Honeywell logo; BDP part no. P272-2786; used with Q674E1304. Y594G1419a E-W2 jumper required. L1034 203 Obsolete. McQuay logo; part no. 60687201; °F/°C scaleplate; H1 anticipator factory set at 0.83A; used with Q674C1280. Y594G1419a Wiring differences (old=new): Y=Y1, W=B, A=X1; remove Y1-W1 jumper. L1059 215, 213 Obsolete. Carrier logo; part no. HH07AT192; used with Q674B1448 (HH93A2202) or Q674C1413 (HH93AZ204). See OEM for replacement. L1067 203 Obsolete. AAF/Snyder General logo; part no. 066804402; H1 anticipator factory set at 0.83A; used with Q674C1280. Y594G1419a L1075 203 Obsolete. McQuay logo; part no. 073318601; Premier White® color; °F/°C scaleplate; includes AAF insert. See OEM for replacement. T874N a Trade Model Replacement Description Wiring differences (old=new): Y=Y1, W=B, A=X1; remove Y1-W1 jumper. Heat pump model; 2-stage heat; 1-stage cool plus changeover; changeover in heat mode. N1008 178 Obsolete. Williamson logo; used with Q674F1196; used in Y594N1007. T874N1016 N1016 178 Honeywell Heat Pump Thermostat logo; used with Q674F1220. T874N1016 N1024 179, 217 Bard logo; H1 and C1 anticipation fixed; used with Q674F1261. None Both the thermostat and subbase must be replaced. 60-2485—8 E-W2 jumper required. 64 See subbase description for replacement information. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. N1040 179 Obsolete. Honeywell logo; H1 and C1 anticipation fixed; used with Q674F1261; used in Y594N1015. None N1057 178 Obsolete. Intertherm logo; part no. 9111882; used with Q674F1220; used in Y594N1023. T874N1016 N1065 178 Obsolete. Miller logo; Nordyne part no. 9122240; used with Q674F1220; used in Y594N1031. T874N1016 T874P P1006 Remarks Heat pump model; 2-stage heat, 1-stage cool, automatic changeover in cool. 57, 78 Obsolete. McQuay logo; part no. 860-442725B-00; 8°F (4.4°C) interstage differential between H1 and H2; used with Q674B1273, C1140. None See subbase description for replacement information. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; includes night setback. P1014 78 Obsolete. Friedrich/Climate Master logo; °F/°C scaleplate; 8°F (4.4°C) differential between H1 and H2 for night setback; used with Q674C1207. P1022 97 Obsolete. Friedrich/Climate Master logo; part no. AT5922; °F/°C scaleplate; 8°F (4.4°C) differential between H1 and H2 for night setback; used with Q674C1215. None See subbase description for replacement information. P1030 97 Obsolete. No logo; Friedrich part no. AT5930; 8°F (4.4°C) differential between H1 and H2 for night setback; used with Q674C1215. None See subbase description for replacement information. 68, 97 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AT205; °F/°C scaleplate; heat interstage differential 8°F (4.4°C). None See subbase description for replacement information. P1055 T874Q 1-stage heat; used with another T874 for night setback. Q1005 44 Honeywell logo. T874A1036 Q1013 44 Obsolete. Lennox logo; part no. 13F1201; °F/°C scaleplate. T874A1036 Replacement has °F scaleplate. Q1021 44 Obsolete. Lennox logo; part no. 13F1301; °C scaleplate. T874A1036 Replacement has °F scaleplate. T874R a Trade Model Replacement Description Heat pump model; 2-stage heat, 1-stage cool, manual changeover. R1004 47 Obsolete. Honeywell logo; used with Q674B1042; used in Y594R1029. Y594R1243a Wiring differences (old=new): W1=W2. R1012 47 Obsolete. Honeywell logo; Addison heat pump; used with Q674B1109. Y594R1243a Wiring differences (old=new): W1=W2. R1020 102 Obsolete. Lennox logo; part no. 24F5401; °F/°C scaleplate; H1 and C1 anticipators are fixed; auxiliary heat circuit powered by separate transformer; used with Q674L1025. Y594R1243a Wiring differences (old=new): M=Y, F=G, V-VR=R, Y=W2, R=O; replacement has °F scaleplate. R1038 102 Obsolete. Lennox logo; °C scaleplate; H1 and C1 anticipators are fixed; auxiliary heat circuit powered by separate transformer; used with Q674L1025. Y594R1243a Wiring differences (old=new): M=Y, F=G, V-VR=R, Y=W2, R=O; replacement has °F scaleplate. R1046 120, 101 Obsolete. York logo; part no. 2TH11702224A; H2 anticipator is fixed; used with Q674L1272 in Y594R1011 or with Q674L1094. Y594R1664a R1053 109 Obsolete. Honeywell logo; H2 anticipator is fixed; used with Q674L1140; used in Y594R1136. Y594R1763a Designed for use on Trane heat pumps. R1061 104 Obsolete. Honeywell logo; H2 anticipator is field adjustable; changeover in cooling; used with Q674L1082. Y594R1243a Replacement has auto fan in Emergency Heat mode. Both the thermostat and subbase must be replaced. 65 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. a Model Number Fig. No. Trade Model Replacement R1079 123 Obsolete. Ruud logo; part no. UXMT-C70; used with Q674L1157. Y594R1243 R1087 120 Obsolete. Honeywell logo; Special for Dunham Bush; use with Q674L. Y594R1664a R1095 123 Obsolete. Rheem logo; part no. RXMT-C70; used with Q674L1157. T874R1152/ Y594R1243a R1103 104 Obsolete. Westinghouse logo; used with Q674L. Y594R1243a R1111 116, 104 Obsolete. Marvair logo; H2 anticipator factory set at 1.2A; used with Q674L1215, L1082; used in Y594R1128. Y594R1243a Replacement has auto fan in Emergency Heat mode. R1129 113 Bard logo; used with Q674L1181. Y594R1243a Wiring differences (old=new): X1=X. R1137 108, 125 Obsolete. Honeywell logo; Heil Quaker part no. HQ711597HW; used with Q674L1132; used in Y594R1110. Y594R1292a R1145 120 Obsolete. York logo; °C scaleplate; H2 anticipator is fixed; used with Q674L1272; used in Y594R1102. Y594R1664a R1152 115 Honeywell logo; used with Q674L1207, L1033; used in Y594R1243. Y594R1243a R1160 182 Obsolete. Honeywell Advanced Heat Pump System logo; used with Q674L1298 and W89. R1178 110, 111 Obsolete. Lennox logo; part no. 24F5601; °F/°C scaleplate; auxiliary heat circuit powered by separate transformer; fast cycle stage H2 anticipator; requires outdoor reset and independent circuits; used with Q674L1165, L1355. R1186 182 Obsolete. Honeywell Advanced Heat Pump System logo; used with Q674L1231 and W89. R1194 115 Obsolete. Amana logo; used with Q674L1249 and W89. Y594R1243a R1202 201 Obsolete. Intertherm logo; part no. 9111871; used with Q674L1264 or Q674L1595; used in Y594R1185. Y594R1672a Wiring differences (old=new): W2=W, Z=no connection, K=X, W=G, W1=H, X=B. R1210 101 Obsolete. Roca logo; °C scaleplate; used with Q674L1017. Y594R1243a Wiring differences (old=new): W=W2, X=L, B=X. R1228 120 Obsolete. York logo; part no. 2TH11702524A; °C scaleplate; used with Q674L1272 and C815A1005; used in Y594R1144. Y594R1672a R1236 115 Obsolete. Williamson logo; includes Allen wrench and screws to lock cover; used with Q674L1348. T874R1152 R1244 115 Obsolete. Westinghouse logo; used with Q674L1314 and W89. T874R1152/ Y594R1243a R1251 120 Obsolete. York logo; part no. 2TH11702324A; H2 anticipator is fixed; used with Q674L1272 and C815A1039. Y594R1672a R1269 122 Obsolete. Fedders multi logo; part no. THTX-120-HEHB 88-58-00540-001; used with Q674L1066; used in Y594R1037. Y594R1615a R1285 123 Obsolete. Honeywell logo; Rheem part no. 41-20796-15; used with Q674L1157. Y594R1243a R1301 113 Obsolete. Comfortmaker logo; part no. 1505-714; used with Q674L1181; used in Y594R1417. Y594R1243a Description Both the thermostat and subbase must be replaced. 60-2485—8 66 Remarks a None Y594R1763a Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2. None Wiring differences (old=new): K=E, C=X, W1=B, Z=L. Wiring differences (old=new): X1=X. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. R1319 191 Obsolete. Carrier part no. 42QH400083; used with Q674B1281 on two speed fan applications. See OEM for replacement. R1327 120 Obsolete. Borg-Warner multi-logo; part no. 6TH11702224A; used with Q674L1272; used in Y594R1193. Y594R1672a R1335 106 Obsolete. BDP multi-logo; part no. HH641501; H2 anticipator factory set 1.2A; used with Q674L1405; used in Y594R1201. Y594R1243a R1343 133 Obsolete. Fedders multi-logo; part no. THTX-120-HEHC 88-58-0056-001; used with Q674L1413; used in Y594R1219. Y594R1425a Wiring differences (old=new): K=E, C=X1, Z=L; remove Y1-W1 jumper. R1350 113 Obsolete. Honeywell logo; used with Q674L1181. Y594R1243a Wiring differences (old=new): X1=X. R1368 125 Obsolete. Coleman logo; part no. 3600-368; used with Q674L1421; used in Y594R1235. Y594R1797a R1376 115 Honeywell logo; °C scaleplate; used with Q674L1207. T874R1152 R1384 131, 135 Obsolete. Carrier Heat Pump System Control logo; part no. HH07AQ170; used with Q674L (HH93AZ187), Q674L (HH93AZ197), or Q674L (HH93AZ198). Y594G1243a Wiring differences (old=new): C=X. R1392 128 Obsolete. Williamson logo; used with Q674L1447; used in Y594R1250. Y594R1425a Wiring differences (old=new): A=L. R1400 113 Obsolete. LSI part no. 104710001; used with Q674L1181, L1462. R1426 136 Obsolete. Trane Weathertron Heat Pump logo; part no. BAYSTAT339 (WY28X0112); °F/°C scaleplate; used with Q674L1496; used in Y594R1284. Y594R1763a R1434 134 Ruud logo; part no. 41-20796-32; used with Q674L1504; used in Y594R1649. Y594R1300a R1442 134 Rheem logo; part no. 41-20796-28; used with Q674L1504; used in Y594R1631. Y594R1300a R1459 134 Obsolete. Honeywell logo; Rheem part no. 41-20796-25; used with Q674L1504. Y594R1300a R1467 108 Honeywell logo; used with Q674L1512; used in Y594R1292. Y594R1292a R1475 123 Honeywell logo; scale range 42°F to 88°F; used with Q674L1520; used in Y594R1300. Y594R1300a R1483 130 Obsolete. Comfortmaker logo; °F/°C scaleplate; used with Q674L1538 and C815A1005; used in Y594R1318. Y594R1763a R1491 137 Obsolete. Honeywell logo; TRADELINE model; used with Q674L1553; used in Y594R1326. Y594R1615a R1509 47 Obsolete. Slant/Fin logo; used with Q674B1042; used in Y594R1334. Y594R1243a Wiring differences (old=new): W1=W2. R1517 130 Obsolete. Arcoaire logo; part no. 150671; used with Q674L1538 and C815A1005; used in Y594R1342. Y594R1763a Wiring differences (old=new): W1=W, E=X2, X=F, C=B. R1525 113 Obsolete. Arcoaire logo; used with Q674L1181; used in Y594R1359. Y594R1243a Wiring differences (old=new): X1=X. R1541 67 Obsolete. Goettl logo; part no. 372071; used with Q674B1349. Y594R1300a R1558 134 Obsolete. Universal Parts logo; part no. 41-20796-45; used with Q674L1504; used in Y594R1623. Y594R1300a R1566 130 Obsolete. Honeywell logo; used with Q674L1538 and C815A1005; used in Y594R1375. Y594R1763a aBoth Trade Model Replacement Description Remarks See subbase description for replacement information. Wiring differences (old=new): W1=W, E=X2, X=F, C=B. Wiring differences (old=new): W1=W, E=X2, X=F, C=B. the thermostat and subbase must be replaced. 67 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. a Model Number Fig. No. R1574 132 R1582 Trade Model Replacement Description Remarks Obsolete. Comfortmaker logo; part no. 1505739; used with Q674L1538; used in Y594R1383. a Y594R1243 Wiring differences (old=new): C=X, X=L, W=W2. 132 Obsolete. Arcoaire logo; part no. 150739; used with Q674L1538; used in Y594R1391. Y594R1243a Wiring differences (old=new): C=X, X=L, W=W2. R1590 115 Obsolete. Refac logo; used with Q674L1207. T874R1152/ Y594R1243a Replacement has °F scaleplate. R1608 119 Obsolete. Honeywell logo; Intertherm heat pump; used with Q674L1264; used in Y594R1409. Y594R1763a Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. R1616 168 Honeywell logo; SUPER TRADELINE® model; used with Q674L1587; used in Y594R1425. Y594R1425a R1624 200 Obsolete. Honeywell logo; used with Q674L1595; used in Y594R1433. Y594R1243a R1632 134 Obsolete. Honeywell logo; used with Q674L1603. Y594R1243a R1640 115 Obsolete. Hitecsa logo; °C scaleplate; H2 anticipator factory set at 1.2A; used with Q674L1207. Y594R1243a R1657 136 Obsolete. American Standard logo; part no. ASYSTAT651; requires outdoor reset; used with Q674L1611; used in Y594R1441. Y594R1763a R1673 108 Heil logo; part no. 1060321, HAXB004TW01; used with Q674L1132; used in Y594R1466. Y594R1292a R1699 119 Obsolete. Miller logo; used with Q674L1264; used in Y594R1482. Y594R1763a R1707 209 Trol-A-Temp by Honeywell logo; Premier White® color; used with Q674L1678; used in Y594R1490. None See Trol-A-Temp for replacement. R1715 209 Trol-A-Temp by Honeywell logo; used with Q674L1186; used in Y594R1508. None See Trol-A-Temp for replacement. R1723 218 Obsolete. No logo; Snyder General part no. 654958B07; °F/°C scaleplate; used with Q674L1702 and C815A1005; used in Y594R1516. Y594R1672a R1731 108 Obsolete. Inter-City Products logo; part no. HQ11477909HW; used with Q674L1132; used in Y594R1524. Y594R1292a R1749 108 Tempstar logo; part no. 1060322, TAXB004TW01; used with Q674L1132; used in Y594R1532. Y594R1292a R1814 108 Obsolete. Honeywell logo; Keeprite part no. THPC; °C scaleplate; used with Q674L1132; used in Y594R1607. Y594R1292a R1822 230 Honeywell logo; TRADELINE model; used with Q674L1710; used in Y594R1615. Y594R1615a R1830 134 Obsolete. Addison logo; WeatherKing part no. 4120796-61; used with Q674L1504; used in Y594R1656. Y594R1300a R1855 228 Obsolete. Lennox logo; Premier White® color; °C scaleplate; outdoor reset required (use C815A1005); used with Q674L1728; used in Y594R1714. Y594R1763a R1871 120 Honeywell logo; designed to replace Y594R1011 (York part no. 2TH11702224); used with Q674L1736; used in Y594R1664. Y594R1664a Both the thermostat and subbase must be replaced. 60-2485—8 68 Wiring differences (old=new): X=B, Z=F, W2=W, K=X2, W1=O. Replacement has °F scaleplate. Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. Wiring differences (old=new): W1=W, X=X2, C=B. Replacement has °F scaleplate. Wiring differences (old=new): Y1=Y, L=F, W1=W, E=X2, C=B; replacement has °F scaleplate. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. R1889 120 Honeywell logo; designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224), and York part no. 2TH11704024; used with Q674L1736 and C815A1054; used in Y594R1672. Y594R1672 R1897 230 Honeywell logo; Premier White® color; used with Q674L1751; used in Y594R1680. Y594R1680a R1905 120 Obsolete. Honeywell logo; Premier White® color; designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224), and York part no. 2TH11704024; used with Q674L1777 and C815A1054; used in Y594R1698. Y594R1672a Replacement is beige. R1913 120 Obsolete. Honeywell logo; Premier White® color; designed to replace Y594R1011 (York part no. 2TH11702224); used with Q674L1777; used in Y594R1706. Y594R1664a Replacement is beige. R1921 115 Obsolete. Econar logo; used with Q674L1207; used in Y594R1722. Y594R1243a R1939 197 American Standard logo (Trane); part no. ASYSTAT651A; includes outdoor reset; used with Q7674L1801; used in Y594R1748. Y594R1763a R1947 168 Obsolete. Inter-City Products logo; part no. HQ1149406HW; used with Q674L1819; used in Y594R1755. Y594R1425a R1954 197 Honeywell logo; TRADELINE model; includes outdoor reset; used with Q674L1827; used in Y594R1763. Y594R1763a Direct replacement for Y594R1748 (T874R1939/ Q674L1801) American Standard logo (ASYSTAT 651A) and Y594R1136 (T874R1053/Q674L1140). R1962 115 Obsolete. Consolidated Industries logo; part no. 9036100; Premier White® color; used with Q674L1843; used in Y594R1771. Y594R1680a Includes CHECK LED. R1970 120 York logo; Canada; Premier White® color; °C scaleplate; used in Y594R1789; used with C815A1039. Y594R1672a Replacement has °F scaleplate. R1988 125 Honeywell logo; TRADELINE model; used with Q674L1868; used in Y594R1797. Y594R1797 Direct replacement for Y594R1235 (T874R1368/ Q674L1421) Evcon/Coleman part no. 3600-368. R2002 245 Obsolete. Amana Air Conditioning logo; part no. 10574102; used in Y594R1805. Y594R1797 Wiring differences (old=new): C/X=X. R2010 245 Obsolete. Amana Air Conditioning logo; part no. 10574104. Y594R1797 Wiring differences (old=new): C/X=X, W3=W2. R2028 209 Obsolete. York logo; part no. 2TH11703424A; used with Q674L1918 in Y594R1821. Y594R1797 R2036 134 Ruud logo; °C scaleplate; used with Q674L1504. See OEM for replacement. 223 Obsolete. Carrier Synergy 2000 Heat Pump System Control logo; used with Q674F1501. 69 Obsolete. No logo; Carrier part no. HH07AT177; used with Q674R1003. T874S S1001 a Remarks a 2-stage heat, 3-stage cool. T874V V1008 Trade Model Replacement Description T8611M2025 Includes night setback. (programmable) or see OEM for direct replacement. 1-stage cool. T874A1036 Both the thermostat and subbase must be replaced. 69 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8. T874 Cross Reference. Model Number Fig. No. T874W Trade Model Replacement Description Remarks 3-stage heat, 2-stage cool, manual changeover. W1007 118 Obsolete. Honeywell logo; Westinghouse special; used with Q674L1256. W1015 54 Honeywell logo; used with Q674B1216 and C815A1005; used in Y594W1014. T874W1015 W1023 233 Obsolete. Lennox Advanced Heat Pump System logo; used with Q674L1280 and W89. T874W1015 W1031 140 T8611M2025 Includes night setback. Obsolete. No logo; Rheem part no. 41-20797-20; used with Q674L1546 and C815A1005; used in Y594W1022. (programmable) W1049 100 Obsolete. McQuay logo; part no. 61202501; 12°F interstage differential between H2 and H3 for night setback; used with Q674C1363. W1056 220 Obsolete. McQuay/Snyder General logo; part no. 1202501; 12°F differential between H2 and H3 for night setback; used with Q674C1363 (61202502). See OEM for replacement. W1064 220 Obsolete. AAF/Snyder General logo; part no. 066804408; 12°F differential between H2 and H3 for night setback; used with Q674C1363 (66804408). See OEM for replacement. W1072 140 Obsolete. Honeywell logo (Inter-City Products); used in Y594W1030. W1080 220 McQuay logo; part no. 073318901; Premier White® color; 12°F differential between H2 and H3 for night setback. W1106 247 Obsolete. Addison logo; part no. 843-277; °F/°C scaleplate; used with Q674L1934 in Y594W1055. T874Y T8611M2025 Includes night setback. (programmable) T8611M2025 Includes night setback. (programmable) T8611M2025 Includes night setback. (programmable) None T8611M2025 Heat pump model; 2-stage heat, 2-stage cool, heat or cool auto changeover. Y1005 210 Obsolete. Mammoth Water Source Heat Pump logo; used with Q674E1353; used in Y594Y1004. See OEM for replacement. Y1013 248 Obsolete. WaterFurnace logo; part no. TA21H03; Premier White® color; °F/°C scaleplate; used with Q674F1675 (32003081). See OEM for replacement. aBoth the thermostat and subbase must be replaced. 60-2485—8 70 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. Q674A Q674 Trade Replacement Description Remarks System: HEAT-AUTO-COOL; Fan: AUTO-ON A1001 71 Standard OEM. Q674A1019 A1019 71 TRADELINE® model; used with T874A-D. Q674A1019 A1035 71 Obsolete. Trane part no. BAS-0435; used with T874A-D. Q674A1019 A1043 71 Honeywell logo; TRADELINE model; Q674A1019 A1050 71 Obsolete. Standard OEM. Q674A1043 Q674B System: HEAT-OFF-COOL; Fan: AUTO-ON B1000 45 Standard OEM; used with T874C1570, C1695, C1703, D1843; used in Y594C1363. Q674B1034 B1018 44 Standard OEM; used with T874B1035, D1082; used in Y594B1026, D1016. Q674B1018 B1026 45 Obsolete. System: HEAT-OFF-RESET-COOL. Q674B1034 B1034 45 TRADELINE Q674B1034 B1042 47 Obsolete. Used with T874R1004, R1509; used in Y594R1029, R1334. Y594R1243a Wiring differences (old=new): W1=W2. B1059 45 Obsolete. Factory installed RC-RH jumper; used with T874C1059; used in Y594C1256. Q674B1034 Field wire RC-RH. B1075 46 Auto fan in heating and cooling mode; used with T874B1035, C1000, D1082; used in Y594D1040. Q674B1075 B1083 51 Obsolete. Carrier part no. HH93AZ178; factory installed RC-RH jumper. Q674B1075a B1091 45 Obsolete. Carrier part no. HH93AZ184; factory installed RC-RH jumper. Q674B1034 B1109 47 Obsolete. Addison heat pump; used with T874R1012. Y594R1243a B1117 44 Obsolete. Carrier part no. HH93AZ180; factory installed RC-RH jumper. Q674B1018a B1125 53 Obsolete. York part no. 2TB04700324A; used with T874D1041. Q674B1075a B1133 48 Obsolete. Includes FILTER LED; used with T874D1082; used in Y594D1156. Q674B1018 B1141 51 Trane part no. BAY28X185; automatic fan operation in heat and cool mode. Q674B1075 Set T874 H1 anticipator for combined load of heat relay and fan relay. B1158 50 Obsolete. Used with T874G1071. T874C1018/ Q674B1018a W1-Y1 and RH-RC jumpers required. B1166 249 Carrier part no. HH93AZ179; factory installed RC-RH jumper; LOCKOUT LED; used with T874C1075 (HH07AT170). Y594C1421 or Replacement only requires Q674B1075a one transformer and has no LOCKOUT LED. B1190 52 Obsolete. Wards special; factory installed RH-RC and F-W3 jumpers; used with T874C1372. Gas Furnace: Q674B1034 One system transformer only. Wiring differences (old=new): W1=W2. Jumper RC-RH; replacement has no LOCKOUT LED. Electric Furnace: Q674B1075 a B1208 187 Obsolete. Used with T874C1422. B1216 54 Used with T874W1015 and C815A1005; used in Y594W1014. Q674B1216 None B1224 49 Obsolete. Lennox part no. 25F7301; four LEDs; used with T874C1430. Q674B1034 Replacement has no LEDs. Both the thermostat and subbase must be replaced. 71 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. Q674 Trade Replacement B1240 234 Obsolete. Northrup heat pump; AUX HEAT LED; used with T874G1139. Y594G1252 Wiring differences (old=new): Y1=Y2, W1=W2; EM HT system switch position is not operational. B1257 56 Obsolete. LSI-Mammoth; RESET LED; automatic fan operation in heat and cool modes; used with T874C1471; used in Y594C1314. Q674B1075 Replacement has no LED. B1273 57 Obsolete. McQuay part no. 860-442727B-00; System: OVERRIDE-HEAT-OFF-COOL; used with T874P1006. T874A1036/ Q674B1075a Wiring differences (old=new): Y=Y1, L=R, W=O; jumper Y1W1; no night setback. Description a Remarks T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. B1281 a 191 Obsolete. Carrier no. 42QH400103; System: HEATOFF-COOL; Fan: LOW-HI-CONT; international symbols on switches; used with T874R1319. See OEM for replacement. B1299 46 Obsolete. Heil Quaker part no. HQ521714HW. Q674B1075 B1307 62 Obsolete. Includes two LEDs; used with T874F1122. T874F1015/ Q674D1040a B1315 68 Obsolete. Friedrich part no. AQ5215; OVERRIDE and SERVICE LEDs; used with T874P1022, P1030. B1331 65 Obsolete. Includes two LEDs; used with T874A1002. Q674B1034 B1349 67 Obsolete. Goettl part no. 372072; used with T874R1541. Y594R1300 B1356 138 Obsolete. Carrier part no. HH93AZ192; used with T874L1018 (HH07AT178). See OEM for replacement. B1372 44 Obsolete. Trane part no. BAS-0427; used with T874A-D. Q674B1018 B1380 46 Obsolete. Trane part no. BAS-0426; used with T874A-D. Q674B1075 B1398 48 Obsolete. Trane part no. BAS-0431; FILTER LED; used with T874A-D. Q674B1034 Replacement has no LEDs. B1406 172 Obsolete. Carrier part no. HH93AZ200; FAULT and CHECK FILTER LEDs; used with T874H1070 (HH07AT166), T874H1088 (HH07AT167) or T874H1153 (HH07AT167); used in Y594H1046. T874A1150/ Q674B1075a Wiring differences (old=new): Y=Y1; jumper W1-Y1; replacement has no LEDs. Replacement has no LEDs. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; set dual fuel switch to electric heat; night setback. Replacement has no LEDs. a B1414 51 American Standard (Trane) part no. ASYSTAT1617. Q674B1075 B1448 215 Obsolete. Carrier part no. HH93A2202; Fan: Lo-MedHigh-On; used with T874L1059. See OEM for replacement. B1455 214 Obsolete. Carrier part no. HH93AZ208; Fan: Lo-MedHigh-On; used with T874A1424 (HH07AT194). See OEM for replacement. B1463 45 Trol-A-Temp; used with T874D1801. B1471 45 Trol-A-Temp; used with T874D1827. B1513 53 Obsolete. TRADELINE; exact replacement for Q674B1125 (York part no. 2TB04700324). Q674B1075 Jumper RC-RH; replacement has no LOCKOUT LED. B1521 53 Obsolete. Carrier Canada part no. HH93AZ179-W; gray color; includes LOCKOUT LED and removable jumpers between RC and RH terminals. Q674B1075 Jumper RC-RH; replacement has no LOCKOUT LED; beige color. B1539 45 Obsolete. Carrier part no. HH93AZ139; used with T874D2049; used in Y594D1370. Q674B1034 B1547 237 Obsolete. TRADELINE; gray color; used with T874C1810; used in Y594C1389. Y594C1389 Both the thermostat and subbase must be replaced. 60-2485—8 72 None See Trol-A-Temp. None See Trol-A-Temp. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. B1554 82 Obsolete. TRADELINE; includes LOCKOUT LED and removable jumpers between RC and RH terminals; used with T874C1877; used in Y594C1421. Y594D1347 B1562 45 Obsolete. Amana logo; part no. P1217701F; removable jumpers between RC and RH terminals. Q674B1034 B1570 45 Obsolete. Armstrong logo; part no. 03299A18. Q674B1034 Replacement is beige. B1588 45 Obsolete. Standard OEM. Q674B1034 Replacement is beige. Q674C C1009 Q674 Trade Replacement Description Remarks Jumper RH-RC; system switch: Off-HEAT-AUTOCOOL. System: OFF-AUTO; Fan: AUTO-ON 72 C1017 Standard OEM; used with T874D1082; used in Y594D1024. Q674C1058 Obsolete. Includes factory-installed RC-RH jumper; used with T874A,F,Q. Q674C1058 C1033 72 Trane part no. BAY28X187. Q674C1058 C1041 74 Obsolete. Command Aire heat pump; used with T874H1005, H1054. Y594H1012a C1058 72 TRADELINE Q674C1058 C1066 73 Obsolete. Command Aire heat pump; used with T874G1352. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; W-Y jumper required. Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=R; W-Y jumper required; night setback. a C1074 81 Obsolete. Used with T874C1018. Q674C1058 Jumper W2-Y1 and RH-RC. C1090 77 Obsolete. LSI-Mammoth heat pump; used with T874K1001. Y594R1419 a Wiring differences (old=new): RH-RC=R, W1=B, W3=W2, W2=W1; remove Y1-W1 jumper. C1108 143 Obsolete. Northrup special; AUX HEAT LED; used with T874G1139. Y594R1243a Wiring differences (old=new): Y1=Y, W1=W2, C=X. C1116 76 Obsolete. McQuay part no. 02005959; two LEDs; used with T874D1116. Q674C1058 Replacement has no LEDs. C1124 79 Obsolete. LSI-Mammoth heat pump; RESET LED; used with T874G-H; used in Y594G-H. Y594G1294 T8600D2028 C1132 75 Obsolete. McQuay part no. 03005049; spring return momentary system switch position; used with T874A1283. See OEM for replacement. C1140 78 Obsolete. McQuay no. 860-442728B-00; System: OVERRIDE-AUTO-OFF; used with T874P1006. C1157 72 Obsolete. York part no. 2TB04700124A. Q674C1058 C1165 192 Obsolete. McQuay part no. 03005050; spring return momentary system switch position. See OEM for replacement. C1173 96 Obsolete. American Air Filter part no. 4ELN-8787; used with T874C1133. Q674C1058 C1181 76 Obsolete. California heat pump; used with T874C1000. Q674C1058 C1199 163 Obsolete. American Air Filter part no. 4ELN-8788; two LEDs; spring return momentary system switch position; used with T874G1485, G1535. T8600D2028 T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. Replacement has no LEDs. No momentary reset switch. Both the thermostat and subbase must be replaced. 73 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. Q674 Trade Replacement C1207 78 Obsolete. Friedrich; System: OVERRIDE-AUTO-OFF; used with T874P1014. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1215 97 Obsolete. Friedrich part no. AQ5315; System: OVERRIDE-AUTO-OFF; OVERRIDE and SERVICE LEDs; used with T874P1022, P1030. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1223 73 Obsolete. Friedrich part no. AQ5323; used on systems requiring night setback contacts; used with T874G1584. Description Y594H1012a Remarks Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1249 164 Includes MALFUNCTION LED; used with T874H1062; used in Y594H1012. Y594H1012a C1256 73 Obsolete. Used with T874G1618. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. C1264 165 Obsolete. Carrier part no. HH93AZ193; used with T874L1018 (HH07AT178). See OEM for replacement. C1280 181, 203 Obsolete. McQuay heat pump; part no. 60687401; COMP FAULT LED; used with T874K1019, L1034. T8600D2028 C1298 76, 225 Obsolete. McQuay part no. 60684801; SERVICE LED; used with T874A1523, A1549, D1918. See OEM for replacement. C1306 75 Obsolete. McQuay part no. 60685001; SERVICE LED; spring return momentary system switch position; used with T874A1325. See OEM for replacement. C1314 72 Obsolete. Trane part no. BAS-0429; used with T874A-F. Q674C1058 C1322 173 Obsolete. Carrier part no. HH93AZ199; FAULT and CK FILTER LEDs; used with T874H1070 (HH07AT166), T874H1088 (HH07AT167) or T874H1153 (HH07AT167); used in Y594H1053. Y594H1012a Wiring differences (old=new): 2=X. C1330 177 Obsolete. LSI-Mammoth part no. 71115201; RESET LED; used on systems with night setback contacts; used with T874G1659, H1096; used in Y594G1427, H1020. Y594H1012a Wiring differences (old=new): R1=R; R2=L. C1355 74 Friedrich part no. AQ355; SERVICE LED; used with T874H1112. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. C1363 99 Obsolete. McQuay part no. 61202601; SERVICE LED; auto fan in heat and cool mode; used with T874C. T874C1125/ Q674B1075a Replacement has HEAT-OFFCOOL. 219 Obsolete. Used with T874C. See OEM for replacement. 220 Obsolete. Used with T874W. See OEM for replacement. 100 Obsolete. Used with T874W. 72 American Standard part no. ASYSTAT616. C1371 a T8611M2025 Includes night setback. (programmable) Both the thermostat and subbase must be replaced. 60-2485—8 See thermostat description for replacement information. 74 Q674C1058 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. Q674 Trade Replacement C1389 205, 176 Obsolete. Command Aire part no. P1099-0021; two LEDs; used with T874G-H. None See thermostat description for replacement information. C1397 205, 171 Obsolete. Command Aire part no. P1099-0023; used with T874G-H. None See thermostat description for replacement information. C1413 213 Obsolete. Carrier part no. HH93AZ204; Fan: Lo-MedHigh-On; used with T874L1059. See OEM for replacement. C1439 217 Obsolete. Bard part no. 8404-016; used with T874N1024. See OEM for replacement. C1454 163 Obsolete. Climate Master part no. AQ5354; two LEDs; spring return momentary system switch position. Y594G1393a Description Remarks No momentary reset switch. C1462 25 Climate Master Special. Q674C1058 Replacement has no LEDs. C1470 221 Obsolete. Climate Master part no. RQ5370; used with T874H1138. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; replacement has MALFUNCTION LED only. C1496 74 Obsolete. Carrier part no. HH93AZ213; includes SERVICE LED; used with T874H1161; used in Y594H1038. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required. C1504 83 Obsolete. Carrier part no. HH93AZ214; used in Y594. Y594H1012a Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=R; W-Y jumper required; night setback. C1512 97 Obsolete. Carrier part no. HH93AZ216; System: Override-Auto-Off; includes two LEDs; used in Y594. C1520 72 Obsolete. Carrier part no. HH93AZ210; used with T874D2049; used in Y594D1388. Q674C1058 C1538 163 Climate Master part no. AQ5354; System: Off-AutoOverride; includes two LEDs and momentary spring position. Y594G1393 No momentary reset switch. C1546 76, 225 Obsolete. McQuay part no. 060684802; gray color; includes one LED. Q674C1058 Replacement has no LEDs; beige color C1553 181, 203 Obsolete. McQuay logo; part no. 073319901; includes one LED. Q674C1058 Replacement is beige. C1561 76 McQuay logo; part no. 073319701; includes one LED. See OEM for replacement. C1579 99, 100 McQuay logo; part no. 073320001; includes one LED. See OEM for replacement. C1595 72 Obsolete. Standard OEM. Q674C1058 Q674D D1008 System: None; Fan: None 55, 66 Obsolete. Used with T874D1082, F1056; used in Y594D1057. Q674D1040 D1016 55 Obsolete. Carrier part no. HH93AZ170; RC-RH jumper. Q674D1040 RC-RH jumper required. D1032 58 Obsolete. Borg-Warner; used with T874G. T874D1165/ Q674D1040a Wiring differences (old=new): Y=Y2, O=Y1, W=W2; jumper W1-Y2 required. D1040 55 TRADELINE Q674D1040 D1057 a T8600D2028 Wiring differences (old=new): (programmable) L=R, W=O; W-Y jumper required; night setback. 55, 66 Obsolete. York part no. 2TB04700424A. Q674D1040 Both the thermostat and subbase must be replaced. 75 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. D1065 63 Obsolete. Includes two LEDs; used with T874F1122. T874F1015/ Q674D1040a D1099 55, 66 Obsolete. Trane part no. BAS-0430; used with T874A-F. Q674D1040 D1107 55, 66 Obsolete. Snyder General part nos. 654958801/ 1520503/ 4ELN30070. Q674F1040. D1115 208 D1123 208 Trol-A-Temp; gray color; used with T874D1827. D1156 55 Obsolete. Gray color; includes removable jumper between RC and RH terminals. Q674D1040 D1164 66 Obsolete. Carrier part no. HH93AZ211; used in Y594D1440. Q674D1040 D1172 208 Obsolete. Amana logo; part no. P121501F; removable jumpers between RC and RH terminals. Q674D1040 D1180 55 Obsolete. York logo; part no. 2TH04703224A. Q674D1040 D1198 Trol-A-Temp; used with T874D1801. None 55, 66 Obsolete. Standard OEM. Q674E a Q674 Trade Replacement Description None T874D1165/ Q674D1040 Remarks Replacement has no LEDs. See Trol-A-Temp. See Trol-A-Temp. Replacement is beige color. Replacement is beige color. System: OFF-HEAT-AUTO-COOL; Fan: AUTO-ON E1007 82 Used with T874D1504; used in Y594D1180. Q674E1049 E1015 84 Obsolete. Lennox heat pump; used with T874G1006, G1154. Y594G1252a E1049 193 TRADELINE; used with T874D2031 and TG504A1025; used in Y594D1354. Q674E1049 E1056 82 Obsolete. Amana part no. D68535-7; used with T874C1059, C1331; used in Y594C1009. Q674E1049 E1064 83 Obsolete. RC-RH jumpered internally; EM HEAT LED. Q674E1049 E1072 82 Carrier part no. HH93AZ176; RC-RH jumpered internally. Q674E1049 E1080 82 Trane part no. BAY28X184. Q674E1049 E1098 85 Obsolete. Used with T874A-D. Q674E1049 E1106 185 Obsolete. ITT Nesbitt. See OEM for replacement. E1114 87 Carrier part no. HH93AZ177; RC-RH jumper; LOCKOUT LED to indicate compressor lockout; used with HH07AT series thermostats. Q674E1049 RC-RH jumper required; replacement has no LED. E1122 83 Obsolete. Square D part no. 63600-002-10; CHECK LED. Q674E1049 Replacement has no LED. E1148 86 Obsolete. Lennox heat pump; used with T874G1014, G1022. Y594G1252a Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R; must use single transformer. E1155 88 Obsolete. Lennox part no. 91C7501; HIGH and LOW LEDs; used with T874B1076, D1017. Q674E1049 Replacement has no LEDs. E1197 89 Obsolete. McQuay part no. 02005961; two LEDs; used with T874D1116. Q674E1049 Wiring differences (old=new): D=O; replacement has no LEDs. E1205 80 Obsolete. Fedders special; SERVICE LED; used with T874D1462. Q674E1049 Replacement has no LEDs. E1213 82 York part no. 2TB04700224A. Q674E1403 E1221 82 Heil Quaker part no. HQ712003HW. Q674E1049 Both the thermostat and subbase must be replaced. 60-2485—8 76 Wiring differences (old=new): R=O, M=Y, F=G, V=R, Y=W2; E-W2 jumper required. RC-RH jumper required. RC-RH jumper required. RC-RH jumper required. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. Remarks E1262 82 Lennox part no. 13F1701. Q674E1049 E1270 198 Obsolete. Carrier part no. HH93AZ189; used with T874L1000 (HH07AT176). Y594G1419a E-W2 jumper required. E1304 82 Obsolete. BDP part no. P272-1887; used with T874L1026. Y594G1419a E-W2 jumper required. E1312 224 Obsolete. McQuay part no. 60684901; one LED; used with T874A1523, A1549, D1686, D1918. Q674E1049 Replacement has no LEDs. E1320 82 Obsolete. Trane part no. BAS-0434. Q674E1049 E1338 88 Obsolete. Goodman part no. CHTS36-60; HIGH and LOW LEDs; used with T874B1100; used in Y594B1042. Q674E1049 E1346 82 Obsolete. Snyder General part nos. 1505753/1506753/ 654958B02; used with T874D1769; used in Y594D1297. Q674E1049 E1353 210 Obsolete. Mammoth; used with T874Y1005; used in Y594Y1004. T8611M2025 Replacement has no LEDs. E1379 212 Trol-A-Temp by Honeywell; used with T874A1465. None E1395 222 Obsolete. Carrier part no. HH93AZ209; used with T874B1134 (HH07AT199). T874B1019/ Q674E1049a E1403 82 TRADELINE; designed to replace York 2TH04701024; used with T874D1942; used in Y594D1347. Y594D1347a E1411 82 Obsolete. Carrier Canada part no. HH93AZ176-W; gray color; removable jumper between RC and RH terminals. Q674E1049 RC-RH jumper required. Replacement is beige color. E1429 87 Carrier Canada part no. HH93AZ177-W; gray color; includes LOCKOUT LED; removable jumper between RC and RH terminals. Q674E1049 RC-RH jumper required. Replacement has no LOCKOUT LED and is beige color. E1445 82 Obsolete. Carrier part no. HH93AZ217-W; gray color; removable jumper between RC and RH terminals. Q674E1049 RC-RH jumper required. Replacement is beige color. E1460 224 McQuay logo; part no. 073319801; includes one LED. E1478 82 Obsolete. Armstrong logo; part no. 03299A19. Q674E1049 RC-R jumper required. Replacement is beige color. E1486 82 Obsolete. Standard OEM. Q674E1049 RC-R jumper required. Replacement is beige color. Jumper E-X2. Q674F a Q674 Trade Replacement Description See Trol-A-Temp. Wiring differences (old=new): W1 =W; RC-RH jumper required; replacement has no LEDs. System: EM.HT.-HEAT-AUTO-COOL-OFF; Fan: AUTO-ON F1006 141 Obsolete. Includes EM HEAT LED; used with T874C1331. Q674F1022 F1022 142 Includes LED and field selectable inserts; used with T874C1059; used in Y594C1017, C1330. Q674F1022 F1030 146 Carrier part no. HH93AZ174; SUPL HEAT LED; used with T874D1074 (HH07AT172). Q674F1022 Wiring differences (old=new): C=X1, X=X2. F1048 149 Obsolete. Includes EM HEAT LED and auxiliary power terminal Z. Q674F1022 Replacement does not include Z terminal and only requires one transformer. F1063 146 Obsolete. Carrier part no. HH93AZ181; SUPL HEAT LED; used with T874D1074 (HH07AT172). Q674F1022 Wiring differences (old=new): C=X1, X=X2. F1071 142 Obsolete. Square D part no. 63600-002-11; CHECK LED. Q674F1022 Both the thermostat and subbase must be replaced. 77 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. a Model Number Fig. No. F1089 152 Q674 Trade Replacement Description Obsolete. Includes EM HEAT LED; X2-E and RC-RH jumpers. Remarks Q674F1022 F1097 142 Obsolete. Southwest special; W2-X2 jumper. Q674F1022 F1105 145 Obsolete. Lennox heat pump; EM HEAT LED; used with T874G1154. Y594G1252a Wiring differences (old=new): V=R, Y=W2, F=G, X2=X, R=O, M=Y; L-E jumper required. F1113 150 Obsolete. Lennox heat pump; part no. 24F6201; V-VR jumper; EM HEAT LED; changeover in cooling; used with T874G1014, G1022. Y59461252a Wiring differences (old=new): R=O, M=Y, F=G, Y=WC, V=VR=R; must use single transformer. F1121 153 Obsolete. Westinghouse heat pump; EM HEAT LED; used with T874G1048. Y594G1252a F1139 148 Obsolete. Tappan heat pump; EM HEAT LED; auto fan in emergency heat mode; used with T874G1147. Y594G1252a F1162 151 Obsolete. Crispaire heat pump; EM HEAT LED; used with T874G. Y594G1393a F1170 153 Obsolete. Heatwave (Southwest Mfg.) heat pump; EM HT LED; used with T874G1105. Y594G1252a F1188 153 Obsolete. Luxaire heat pump. Y594G1252a F1196 178 Obsolete. Williamson; EM HEAT and SERVICE LEDs; used with T874N1008; used in Y594N1007. Q674F1220 F1204 154 Obsolete. Special for Crispaire; EM HEAT and COMP FAULT LEDs; used with T874G1089; used in Y594G1153. Y594G1393a F1212 155 Includes AUX HEAT and EM HEAT LEDs; used with T874G1246, G1451, G1592, G1915; used in Y594G1252. F1220 178 Used with T874N1016; used in Y594N. Q674F1220 F1238 155 Obsolete. Rheem part no. 41-20797-14; AUX HEAT and EM HEAT LEDs; used with T874G1097, G1212, G1220, G1238. Y594G1252a F1246 156 Obsolete. Westinghouse heat pump; EM HEAT and AUX HEAT LEDs; auto fan in emergency heat mode; changeover in cooling mode. Y594G1252a F1253 157 Obsolete. Wesco/Addison heat pump; used with T874G1261, G1279, G1287. Y594G1252a Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L. F1261 179 Includes two LEDs; used with T874N1024; used in Y594N. Y594G1419a Wiring differences (old=new): L=X2, Y=Y1. F1279 158 Obsolete. Westinghouse heat pump; two LEDs; used with T874G. Y594G1252a Wiring differences (old=new): L1=L. F1295 147 Obsolete. Keeprite/Westinghouse heat pump; SERVICE, AUX HEAT and EM HEAT LEDs; used with T874G1188. Y594G1252a Wiring differences (old=new): S=L; replacement does not include A or T terminals. F1311 155 York heat pump; AUX HEAT and EM HEAT LEDs; used with T874G1410. Y594G1252a F1329 142 Obsolete. Heil Quaker part no. HQ712005HW; one LED and field selectable inserts. Q674F1022 F1337 166 Obsolete. WeatherKing heat pump; two LEDs and field selectable inserts; used with T874D1009; used in Y594D1222. Q674F1022 Wiring differences (old=new): R=RC-RH; replacement has no LEDs. F1345 194 Obsolete. Addison heat pump; EM HEAT and CHECK LEDs; used with T874G; used in Y594G. Y594G1252a Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L. Both the thermostat and subbase must be replaced. 60-2485—8 78 Wiring differences (old=new): C=X. Wiring differences (old=new): A=L. Q674F1212 or Y594G1252a T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. a Model Number Fig. No. Q674 Trade Replacement F1360 167 Obsolete. Rheem part no. 41-20797-17; AUX HEAT and EM HEAT LEDs; used with T874G1493. Y594G1526 F1378 195 Obsolete. Includes EM HEAT and AUX HEAT LEDs; used with T874G1501. Y594G1252a Wiring differences (old=new): L1=L; changeover in cooling only. F1394 139 Obsolete. Nepco heat pump; HEAT PUMP and AUX HEAT LEDs; System: AUX HEAT-HEAT PUMP-2 STAGE HEAT-OFF-COOL; used with T874D1595. T874D1165/ Q674B1018a Replacement has HEAT-OFFCOOL system switching and no LEDs. F1402 169 Obsolete. Coleman heat pump; two LEDs; used with T874G1576; used in Y594G1377. Y594G1633a F1410 170 Used with T874G1246, G1915; used in Y594G1393. Y594G1393a F1428 199 Obsolete. Used with T874G1600; used in Y594G1401. Y594G1419a F1436 167 Includes AUX HEAT and EM HEAT LEDs; changeover in heating mode; used with T874G1626; used in Y594G1526. None F1444 227 Includes AUX HEAT, EM HEAT and CHECK LEDs; used with T874G1642; used in Y594G1419. Y594G1419a F1451 204 Obsolete. York part no. 2TB047700524A; one LED and field selectable inserts. Q674F1012 F1477 227 TRADELINE; gray color; used with T874G1741, G1824; used in Y594G1476, G1534. Y594G1476a F1485 211 Trol-A-Temp by Honeywell; changeover is provided by Trol-A-Temp zone panel; used with T874G1758; used in Y594G1492. F1501 223 Obsolete. Carrier two-speed compressor heat pump; used with T874S1001. F1519 231 Obsolete. Nordyne; used with T874G1832, G1840; used in Y594G1542, G1559. Y594G1252a Replacement has auto changeover in cooling mode only. F1535 229 Obsolete. Lennox heat pump; gray color; used with T874G1857; used in Y594G1583. Y594G1161a Wiring differences (old=new): E=X2, C=B, L=F. F1543 204 Obsolete. TRADELINE Q674F1022 Wiring differences (old=new): X2=X, X1=B. F1550 243 Obsolete. Amana part no. 10573901; includes two LEDs; used with T874G1899; used in Y594G1591. Y594G1633 F1568 155 Obsolete. Gray color; includes two LEDs; used with only T874G1931. Y594G1476 F1584 169 TRADELINE; includes two LEDs; used with T874G1972; used in Y594G1633. Direct replacement for Coleman/Evcon Y594G1377 (T874G1576/ Q674D1402); Coleman part no. 3600-373. Y594G1633a F1592 238 Heat Controller; Fan: AUTO-ON; System: AUX HEATHEAT PUMP- 2 STAGE HEAT-OFF-COOL; includes two LEDs; used with T874C1844; used in Y594C1413. Y594R1425 E-W2 jumper required; system switch: EM.HT.-HEAT-OFFCOOL. F1600 169 Obsolete. Amana part no. 10573903; includes two LEDs; used with T874G1980; used in Y594G1641. Y594G1633 Wiring differences (old=new); W3=W2. F1634 139 Standard OEM; System: AUX HEAT-HEAT PUMP2 STG HEAT-OFF-COOL; includes two LEDs; used with T874D2155. Y594G1716 F1667 155 WaterFurnace logo; part no. TA21H03; System: OFFAUTO-HEAT-EM HT; includes two LEDs; used with T874G2046. Y594G1716 Description Remarks a None Wiring differences (old=new): jumper W1-Y1. Wiring differences (old=new): X2=X; X1=B. See Trol-A-Temp. T8611M2025 Includes night setback. (programmable) Y1-W1 jumper required. Both the thermostat and subbase must be replaced. 79 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. F1675 248 Obsolete. WaterFurnace logo; part no. TA21H03; includes four LEDs. G1005 184 Obsolete. Used in Y594F1063. Q674G1070 G1013 186 Obsolete. Climate Control; used with T874D1298. See OEM for replacement. G1021 91 Obsolete. Includes O and B terminals; used with T874A-F,Q or T874D1082; used in Y594D1032. Q674G1070 G1047 92 Obsolete. Used with T874C1018, C1125. G1054 188 Obsolete. Singer part no. 0200-5963; used with T874D1298. See OEM for replacement. G1062 232 Obsolete. Singer; used with T874D1298. See OEM for replacement. G1070 91 TRADELINE Q674G1070 G1088 92 Obsolete. LSI-Mammoth part no. 71120201; used with T874C. See OEM for replacement. G1096 90 Obsolete. Climate Control part no. 02005958; used with T874D1439, D1447. See OEM for replacement. G1104 94 Obsolete. McQuay part no. 0200-5963; two LEDs; used with T874D1116. See OEM for replacement. G1120 202, 226 Obsolete. McQuay part no. 60684701; two SERVICE LEDs; no fan switching; used with T874D1694, G1926. See OEM for replacement. Q674G Remarks See OEM for replacement. System: OFF-AUTO; Fan: None T8611 G1138 91 Obsolete. Trane part no. BAS-0433; used with T874A-F. Q674G1070 G1153 184 Obsolete. Carrier part no. HH93AZ212; used in Y594D1396. Q674G1070 G1161 184 Gray color. Q674G1070 Replacement is beige color. G1179 202 Obsolete. McQuay logo; part no. 073319601; includes two LEDs. Q674G1161 Replacement has no LEDs. J1001 180 Obsolete. Singer heat pump part no. 02005964; EM HEAT LED; changeover heat mode. See OEM for replacement. J1019 159 Obsolete. Westinghouse heat pump; EM HT LED; System: EM.HT.-ON-OFF; used with T874G1048. Y594G1252a J1027 160 Obsolete. York part no. 025-22291; EM HEAT LED; auto fan in emergency heat mode; changeover in cool mode; used with T874G1170, G1196, G1428, G1345, G1444; used in Y594G1013, G1138, G1229. Y594G1567a J1035 161 Carrier heat pump; part no. HH93AZ173; System: SUPL.HT.-ON-OFF; SUPL HEAT LED; used with T874G1055 (HH07AT171). Y594G1674a J1043 162 TRADELINE heat pump model; designed for use on Trane heat pumps; AUX HT and EM HT LEDs; auto fan in emergency heat; changeover in cooling mode; used with T874G1204 and C815A1008; used in Y594G1161. J1050 183 Obsolete. Westinghouse heat pump; EM HEAT and AUX HEAT LEDs; used with T874G1071. Y594G1674a J1068 144 Obsolete. Carrier heat pump; part no. HH93AZ183; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165). Y594J1019 J1076 180 Obsolete. McQuay part no. 02005964; two LEDs; used with T874A,D. Q674F1022 Q674J a Q674 Trade Replacement Description System: EM.HT.-AUTO-OFF; Fan: AUTO-ON Both the thermostat and subbase must be replaced. 60-2485—8 80 Q674J1043 or Y594G1161a Wiring differences (old=new): W=W2. Designed for use on Trane heat pumps. Replacement has no LEDs. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. J1084 171 Obsolete. BDP heat pump; part no. 34427DP126, P272-1879; EM HEAT LED; used with T874J1010. Y594J1019 Wiring differences (old=new): W1=W2, F=L. J1118 196 Obsolete. Carrier heat pump; part no. HH93AZ188; SUPL HEAT LED; System: SUPL.HT.-ON-OFF; used with T874G1055 (HH07AT171). Y594G1674 Wiring differences (old=new): C=X;Y1=W1; jumper required; no auto fan in emergency heat. J1126 160 Obsolete. Luxaire no. 026-00068-000; EM HEAT LED; used with T874G1568; used in Y594G1351. Y594G1567a J1142 174 Obsolete. American Standard part no. WY28X0250; AUX HEAT and EM HEAT LEDs; used with T874G1675; used in Y594G1443. Y594G1161a J1159 206 Obsolete. Carrier heat pump; part no. HH93AZ196; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165). Y594J1019 J1167 175 Obsolete. Carrier heat pump; MANUAL, AUTO, HEAT PUMP and DEFROST LEDs; System: SUPL HEATON-OFF; used with T874G1717; used in Y507J1201. Y594G1252a Wiring differences (old=new): C=X, D=L; replacement has AUX HEAT and EM HEAT LEDs. J1175 216 Obsolete. Snyder General part nos. 1505756, 1506756; CHECK, AUX HEAT and SYSTEM LEDs; used with T874G1774, G1782; used in Y594G1500, G1518. Y594G1252a Wiring differences (old=new): E=W2, W1=W3, X=E, C=X. J1191 161 Obsolete. Carrier heat pump; gray color; used with T874G1790. Y594G1252a Wiring differences (old=new): C=X; replacement has °F scaleplate. J1209 160 TRADELINE; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424) and York part no. 2TH11704124; used with T874G1865; used in Y594G1567. Y594G1567a J1217 171 Obsolete. Nordyne part no. 9132250; used with T874J1036, J1044. J1225 160 Obsolete. TRADELINE; gray color; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424) and York part no. 2TH11704124; used with T874G1873; used in Y594G1575. Y594G1567a J1241 144 Obsolete. Carrier Canada part no. HH93AZ183-W; gray color; System: SUPL HT-ON-OFF; includes one LED. See OEM for replacement. J1258 161 Obsolete. Carrier Canada part no. HH93AZ173-W; gray color; System: SUPL HT-ON-OFF; includes one LED. Y594G1674a J1266 160 York Canada; gray color; includes EM HT LED; used in Y594G1625. Y594G1567a J1274 161 TRADELINE; System: SUPL HT-ON-OFF; includes one LED; used with T874G2004; used in Y594G1674. Y594G1674 J1282 244 Obsolete. TRADELINE; System: SUPL HT-ON-OFF; includes SUPL HT LED; used with T874J1069; used in Y594J1019. (Recontrol) T8511G1021 Q674K a Q674 Trade Replacement Description Y594J1019 Remarks Wiring differences (old=new): F=L. Replacement is beige. Replacement is beige color. System: OFF-HEAT-AUTO-COOL; Fan: None K1000 93 Obsolete. Carrier part no. HH93AZ172; RC-RH jumper. Q674E1049 K1018 95 Obsolete. Oneida Heater part no. 3040284-02; System: OFF-WOOD-WOOD/OIL-OIL; used with T874F1106. Q674K1026 Fan switch is not operational. Both the thermostat and subbase must be replaced. 81 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. K1026 95 System: OFF-WOOD-WOOD/ OIL-OIL; used with T874F1155. Q674K1026 Remarks K1034 93 Obsolete. Snyder General part no. 4ELN-7920. Q674E1049 Fan switch is not operational. K1042 93 Obsolete. Carrier part no. HH93AZ172-W; gray color; includes removable jumper between RC and RH terminals. Q674E1049 Fan switch is not operational. Q674L a Q674 Trade Replacement Description System: EM.HT.-HEAT-OFF-COOL; Fan: ON-AUTO L1017 101 Obsolete. York heat pump; EM HEAT LED; cooling mode changeover; compressor lockout; auto fan in EM.HT; used with T874R1046. Y594R1243a Wiring differences (old=new): W=W2, X=L, B=X. L1025 102 Obsolete. Lennox heat pump; part no. 24F6101; EM. HEAT LED; V-VR jumper; used with T874R1020, J1038. Y594R1243a Wiring differences (old=new): M=Y, F=G, V-VR=VR, Y=W2, R=O. L1033 115 Obsolete. Rheem heat pump; EM HEAT LED; used with T874R1152. Y594R1243a L1041 103 Obsolete. Carrier heat pump; part no. HH93AZ175; SUPL HEAT LED; used with T874G1055 (HH07AT171), G1071 (HH93AZ175), G1113. Y594G1419 Wiring differences (old=new): C=X, jumper Y1=W1. L1066 122 Obsolete. Fedders heat pump; used with T874R1269; used in Y594R1037. Y594R1615a Wiring differences (old=new): K=E, C=X, W1=B, Z=L. L1074 124 Obsolete. Carrier heat pump; part no. HH93AZ186; SUPL HT LED; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165). Y594J1001 L1082 104 Obsolete. Crispaire heat pump; W2-H jumper; EM HEAT LED; used with T874R1061, R1111. Y594R1243a Replacement has auto fan in emergency heat mode. L1090 105 Obsolete. Fedders heat pump; EM HEAT LED; changeover in heat mode; used with T874C1398, C1406, C1414. Y594R1425a Wiring differences (old=new): K=E, C=X. L1108 106 Obsolete. Westinghouse; EM HEAT LED. Y594R1243a L1116 107 Obsolete. Carrier part no. HH93AZ171; SUPL HEAT LED; used with T874D1264 (HH07AT173). See OEM for replacement. L1132 108 Heil Quaker part no. HQ711598; used with T874R1137, R1673, R1731, R1749, R1814; used in Y594R1110, R1466, R1524, R1532, R1607. Y594R1292a L1140 109 Obsolete. Includes EM HEAT and AUX HEAT LEDs; used with T874R1053; used in Y594G1136. Y594R1763a L1157 115 Obsolete. Rheem part no. 41-20796-14; EM HEAT and AUX HEAT LEDs; used with T874R. Q674L1207a 121 Obsolete. Used with T874C. Y594C1322a 123 Obsolete. Used with T874R. Y594R1243a L1165 110 Obsolete. Lennox no. 24F5901; factory installed V-VR jumper; EM HEAT and SERVICE LEDs; stage 2 heat is isolated; used with T874C1448, R1178 and C815A1013. Y594R1763a L1173 112 Obsolete. Westinghouse; AUX HEAT and EM HEAT LEDs. Y594R1243a L1181 113 Used with T874R1129; used in Y594R. Y594R1243a Both the thermostat and subbase must be replaced. 60-2485—8 82 Designed for use on Trane heat pumps. Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2. Wiring differences (old=new): X1=X. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. a Model Number Fig. No. Q674 Trade Replacement L1199 114 Obsolete. Lennox no. 24F6001; used with T874D1207 T8611M2025 Wiring differences (old=new): and C815A1013. (programmable) V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer. L1207 115 Used with T874R1152, R1590, R1640, R1921; used in Y594R1243, R1706. Q674L1207 or Y594R1243a L1215 116 Obsolete. Crispaire heat pump; used with T874R1111; used in Y594R1128. Y594R1243a L1223 117 Obsolete. Westinghouse special. See OEM for replacement. Description Remarks Replacement has auto fan in emergency heat mode. Wiring differences (old=new): A=L; set anticipator to 1.2. L1231 182 Obsolete. Used with T874R1186 and W89. None L1249 115 Obsolete. Used with T874R1194 and W89. Y594R1243a L1256 118 Obsolete. Westinghouse special; used with T874W1007. T8611M2025 Includes night setback. (programmable) L1264 119 Obsolete. Intertherm heat pump; EM HEAT and SERV LEDs; used with T874R1202, R1608, R1699; used in Y594R1185, R1409, R1482. Y594R1672a or Wiring differences (old=new): Y594R1763a W2=W, X=B, Z=no connection, K=X, W1=H. L1272 120 Obsolete. York part no. 025-22290; used with T874R1046, R1145; used in Y594R1011, R1102; used with T874R1228, R1251 R1327 and C815A1039; used in Y594R1144, R1151, R1193. Y594R1672a L1280 233 Obsolete. Lennox no. 52C7601; used with T874W1023 and W89. Y594W1014a L1298 182 Obsolete. Singer heat pump; used with T874R1160 and W89. See OEM for replacement. L1314 115 Obsolete. Westinghouse heat pump; used with T874R1244 and W89. L1322 127 Obsolete. EM HEAT and AUX HEAT LEDs; used with T874C1455. Y594R1243a L1330 120 Obsolete. York heat pump; used with T874R. Y594R1664a L1348 115 Obsolete. Williamson heat pump; used with T874R1236. Q674L1207 L1355 111, 190 Obsolete. Lennox part no. 31F3201; V-VR jumper; used with T874C1448, R1178 and C815A1015. Y594R1763a Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2. L1363 129 Obsolete. York heat pump; EM HEAT LED; used with T874G1402. Y594R1425a Wiring differences (old=new): W=W2, X=E, B=X; jumper YW1. L1371 124 Obsolete. BDP heat pump; part no. 34427DP125, P272-1878; EM HEAT LED; used with T874J1010. Y594J1001 Wiring differences (old=new): W1=W2, F=L. L1389 114 Obsolete. Lennox part no. 41F6501; V-VR jumper; used with T874D1207. L1397 103 Obsolete. Carrier part no. HH93AZ185A; SUPL HEAT LED. Q674L1207 or Y594R1243a Wiring differences (old=new): L=X, X=B. T8611M2025 Wiring differences (old=new): (programmable) V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer. Y594G1393a Wiring differences (old=new): C=X. Both the thermostat and subbase must be replaced. 83 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. a Model Number Fig. No. Q674 Trade Replacement L1405 106 Obsolete. BDP heat pump; part no. HH641501; used with T874R1335; used in Y594R1201. Y594R1243 L1413 133 Obsolete. Fedders heat pump; used with T874R1343; used in Y594R1219. Y594R1425a L1421 125 Obsolete. Coleman heat pump; used with T874R1368; used in Y594R1235. Y594R1797a L1439 131 Obsolete. Carrier part no. HH93AZ187; SUPL HEAT LED; System: SUPL HT-HEAT- COOL; used with T874R1384 (HH07AQ170). Q674L1207 or Y594G1393a Wiring differences (old=new): C=X. L1447 128 Obsolete. Williamson heat pump; three LEDs; used with T874R1392; used in Y594R1250. Y594R1425a Wiring differences (old=new): A=L. L1454 131 Obsolete. Carrier part no. HH93AZ197; SUPL HEAT LED; used with T874R1384 (HH07AQ170). Y594R1393a Wiring differences (old=new): C=X. L1462 113 Obsolete. LSI heat pump; part no. 104710002; used with T874R1400. Y594R1243a Wiring differences (old=new): X1=X. L1496 136 Obsolete. Trane heat pump; used with T874R1426; used in Y594R1284. Y594R1763a L1504 134 Rheem part no. 41-20796-24; used with T874R1442, R1434, R1459; used in Y594R1631, R1649, R1854. Y594R1300a L1512 108 Includes two LEDs; used with T874R1467; used in Y594R1292. Y594R1292a L1520 123 Includes EM HEAT and AUX HEAT LEDs; used with T874R1475; used in Y594R1300. Y594R1300a L1538 130 Obsolete. Snyder General heat pump; used with T874R1483, R1517, R1566 and C815A1005; used in Y594R1318, R1342, R1375. Y594R1763a Wiring differences (old=new): C=B, W1=W, E=X2, X=F. 132 Obsolete. Used with T874R1574, R1582; used in Y594R1383, R1391. Y594R1243a Wiring differences (old=new): C=X, X=L, W=W2. L1546 140 Obsolete. Rheem part no. 41-20797-21; three LEDs; used with T874W1031 and C815A1005; used in Y594W1022. L1553 137 Obsolete. Includes three LEDs; used with T874R1491; used in Y594R1326. Y594R1615a L1561 121 Obsolete. Used with T874C1638; used in Y594C1322. Y594C1322a Use Y594C1322 when T874C is used. 123 Obsolete. Used with T874R. Y594R1243a Use Y594R1243 when T874R is used. L1579 135 Obsolete. Carrier heat pump; part no. HH93AZ198; SUPL HEAT LED; used with T874R1384 (HH07AQ170). Y594R1243a Wiring differences (old=new): C=X. L1587 168 Used with T874R1616; used in Y594R1425. Y594R1425a L1595 200, 201 Obsolete. Miller heat pump; used with T874R1624 or T874R1202; used in Y594R1433. L1603 134 Obsolete. Used with T874R1632. Y594R1243a L1611 136 Obsolete. American Standard heat pump; part no. WY28X235; used with T874R1657; used in Y594R1441. Y594R1763a L1637 207 Obsolete. Carrier heat pump; part no. HH93AZ195; used with T874J1002 (HH07AT175) or T874J1010 (HH07AT165). Y594J1001a Description Both the thermostat and subbase must be replaced. 60-2485—8 84 Remarks a Wiring differences (old=new): K=E, C=X, Z=L; remove W1-Y jumper. T8611M2025 Includes night setback. (programmable) Y594R1243a or Y594R1763a T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. a Model Number Fig. No. Q674 Trade Replacement L1678 209 Trol-A-Temp by Honeywell; gray color; used with T874R1707; used in Y594R1490. None See Trol-A-Temp. L1686 209 Trol-A-Temp by Honeywell; used with T874R1715; used in Y594R1508. None See Trol-A-Temp. L1702 132 Obsolete. Snyder General heat pump; part no. 654958B07; used with T874R1723 and C815A1005; used in Y594R1516. Y594R1672a L1710 230 Used with T874R1822; used in Y594R1615. Y594R1615a L1728 228 Obsolete. Lennox; gray color; used with T874R1855; used in Y594R1714. Y594R1763a L1736 120 Designed to replace Y594R1011 (York part no. 2TH11702224); used with T874R1871; used in Y594R1664. Y594R1664a Designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224) and York part no. 2TH11704024; used with T874R1889 and C815A1054; used in Y594R1672. Y594R1672a Description Remarks Wiring differences (old=new): C=B, W1=W, X=X2. Wiring differences (old=new): Y1=Y, L=F, W1=W, E=X2, C=B. L1751 230 Gray color; used with T874R1897, used in Y594R1680. Y594R1680a L1769 124 Obsolete. Nordyne part no. 9132260; used with T874J. See OEM for replacement. L1777 120 Obsolete. Gray color; designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224) and York part no. 2TH11704024; used with T874R1905 and C815A1059; used in Y594R1698. Y594R1672a Replacement is beige. Designed to replace Y594R1011 (York part no. 2TH11702224); used with T874R1913; used in Y594R1706. Y594R1664a Replacement is beige. Wiring differences (old=new): C=X; Y1-W1 jumper required. L1785 103 Obsolete. Carrier part no. HH93AZ175-W; Canada; gray color; System: Supl Ht-Heat-Off-Cool; includes one LED. Y594G1476a L1793 124 Obsolete. Carrier Canada part no. HH93AZ186-W; gray color; Fan: Auto-On; System: Supl Ht-Heat-OffCool; includes one LED. Y594J1019a L1801 197 American Standard (Trane) part no. THT1225; includes two LEDs; used with T874R1939; used in Y594R1748. Y594R1763a L1819 168 Obsolete. Inter-City Products part no. HQ1149407HW; includes three LEDs; used with T874R1947; used in Y594R1755. Y594R1425a L1827 197 TRADELINE; includes two LEDs; used with T874R1954; used in Y594R1763; direct replacement for Trane/American Standard Y594R1748 (T874R1939/Q674L1801) Trane part no. ASYSTAT 631A, Y594R1136 (T874R1053/Q674L1140). Y594R1763a L1835 140 Obsolete. Inter-City Products; includes three LEDs; used in Y594W1030. L1843 115 Obsolete. Consolidated Industries part no. 9036100; gray color; includes two LEDs; used with T874R1962; used in Y594R1771. Y594R1680a L1850 120 York Canada; gray color; includes one LED; used with T874R1970; used in Y594R1789. Y594R1672a T8611M2025a Includes night setback. (programmable) Includes CHECK LED. Both the thermostat and subbase must be replaced. 85 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9. Q674 Subbase Cross Reference. Model Number Fig. No. L1868 125 TRADELINE; includes two LEDs; used with T874R1988; used in Y594R1797; direct replacement for Evcon/Coleman Y594R1235 (T874R1368/ Q674L1421) Coleman part no. 3600-368. Y594R1797 L1876 245 Obsolete. Amana part no. 10573902; includes two LEDs; used with T874R2002; used in Y594R1805. Y594R1797 Wiring differences (old=new): C/X=X. L1884 245 Obsolete. Amana part no. 10573904; includes two LEDs; used with T874R2010; used in Y594R1813. Y594R1797 Wiring differences (old=new): C/X=X, W3=W2. L1892 103 Obsolete. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes one LED; used with T874G2004; used in Y594G1666; direct replacement for Carrier Y507J1011 (T874G1055/Q674L1041) Carrier part no. HH07AT171/HH93AZ175. Y594G1674 Replacement has auto changeover. L1900 241 Obsolete. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes SUPL HT LED; used with T874J1069; used in Y594J1001; direct replacement for Carrier T874J1028/Q674J1068 (Carrier part no. HH07AT165/HH93AZ183), Carrier T874J1002/ Q674J1068 (Carrier part no. HH07AT175/ HH93AZ183). Y594J1019 Replacement has auto changeover. L1918 125 Obsolete. York logo; part no. 2TH11703424A; includes two LEDs; used with T874R2028 in Y594R1821. Y594R1797a L1934 123 Obsolete. Addison logo; part no. 843-277; includes three LEDs; used with T874W1106 in Y594W1055. T8611M2025 Q674N System: OFF-HEAT-COOL-EVAP; Fan: AUTO-ON 60 Obsolete. Goettl heat pump; changeover in heat mode; evaporative cooler circuit; used with T874C1182. See OEM for replacement. N1023 61 Obsolete. Sigler heat pump; evaporative cooler circuit; used with T874C1349. See OEM for replacement. P1005 System: SUPL HT-HEAT-COOL; Fan: AUTO-ON 126 Q674Q Obsolete. Carrier heat pump; part no. HH93AZ169; used with T874G1071 (HH07AT171). 59 Obsolete. McQuay special; used with T874A1267. Q1012 64 Used with T874A1291. Q674R 69 None Obsolete. Carrier part no. HH93AZ190; international symbols on fan and switches; used with T874V1008 (HH07AT177). 70 Obsolete. Fiberglas; Canada; SERVICE LED; used with T874C1653; used in Y594C1348. See OEM for replacement. System: OFF-ON; Fan: LO-MED-HI 240 Obsolete. Snyder General part no. 044271801. Both the thermostat and subbase must be replaced. 60-2485—8 See OEM for replacement. System: HEAT-COOL; Fan: None Q674W W1006 See OEM for replacement. System: OFF-COOL; Fan: LO-HI-CONT Q674S S1000 Y594G1419a System: HEAT-OFF-COOL; Fan: LOW-MED-HI-ON Q1004 R1003 Remarks a N1015 Q674P a Q674 Trade Replacement Description 86 See OEM for replacement. Wiring differences (old=new): C=X; jumper Y1-W1; replacement has OFF-EM HTHEAT-AUTO-COOL system switching. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number Fig. No. Trade Model Replacementa Description Remarks Y594A A1001 46 Obsolete. Amana part no. D68535-11; contains T874A1077, Q674B1075. T874A1036/ Q674B1075 A1019 82 Obsolete. Amana part no. P68535-12; contains T874A1077, Q674E1056. T874A1036/ Q674E1049 A1035 44 Obsolete. Trane part no. 268-0187-1; contains T874A1085, Q674B1018. T874A1036/ Q674B1018 A1043 46 Obsolete. Trane part no. 268-0201-5; contains T874A1085, Q674B1075. T874A1036/ Q674B1075 55, 66 Obsolete. Trane part no. 268-0201-3; contains T874A1085, Q674D1008. T874A1036/ Q674D1040 A1050 A1068 82 Obsolete. Sears part no. 42-9144; contains T874A1119, Q674E1007. A1126 64 Contains T874A1291, Q674Q1012. A1159 91 Obsolete. Contains T874A1440, Q674G1005. T874A1150/ Q674G1070 A1167 184 California Economizer; Premier White® color; contains T874A1580 and Q674G1161. T874A1036/ Q674G1070 A1175 55 Obsolete. York logo; part no. 2TH04703224; contains T874A1622, Q674D1180. T874A1010/ Q674D1040 A1191 46 Obsolete. Amana logo: part no. P6853524R; contains T874A1002, Q674B1075. T874A1036/ Q674B1075 B1026 44 Trane part no. BAYSTAT012; contains T874B1035, Q674B1018. T874B1019/ Q674B1018 B1034 46 Obsolete. Trane part no. 163-552-1; contains T874B1035, Q674B1075. T874B1019/ Q674B1075 B1042 88 Obsolete. Goodman part no. CHTS36-60; contains T874B1100, Q674E1338. T874B1019/ Q674E1049 No LEDs on replacement. C1009 82 Obsolete. Amana part no. D68535-9; contains T874C1059, Q674E1056. T874C1018/ Q674E1049 Jumper RC-RH. C1017 142 Obsolete. Amana part no. D68535-10; contains T874C1059, Q674F1022. T874C1018/ Q674F1022 C1058 46 Obsolete. Contains T874C1000, Q674B1075. T874C1018/ Q674B1075 C1082 82 Obsolete. Trane part no. 166-162-1; contains T874C1083, Q674E1007. T874C1018/ Q674E1049 C1256 45 Obsolete. Amana part no. D68535-16; contains T874C1059, Q674B1059. T874C1018/ Q674B1034 C1280 45 Obsolete. Williamson; contains T874C1570, Q674B1000. T874C1018/ Q674B1034 C1314 56 Obsolete. LSI; contains T874C1471, Q674B1257. T874C1018/ Q674B1018 C1322 121 Obsolete. Contains T874C1638, Q674L1561. Y594C1322 C1330 142 Obsolete. Amana part no. D68535-21; contains T874C1059, Q674F1022. T874C1018/ Q674F1022 T874A1036/ Q674E1049 None Replacement is beige color. Y594B Y594C a Jumper RC-RH. Jumper RC-RH; no RESET LED on replacement. Both the thermostat and subbase must be replaced. 87 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number Fig. No. Trade Model Replacementa Description Remarks C1348 70 Obsolete. Fiberglas; contains T874C1653, Q674S1000. T874C1000/ Q674B1075 C1355 45 Obsolete. Nordyne “Miller” part no. 9122250; contains T874C1695, Q674B1000. T874C1018/ Q674B1034 C1363 45 Obsolete. Nordyne “Intertherm” part no. 911100001; contains T874C1703, Q674B1000. T874C1018/ Q674B1075 C1371 184 Obsolete. California Economizer; contains T874C1802 and Q674G1005. T874C1018/ Q674G1070 C1389 237 Obsolete. TRADELINE; Premier White® color; contains T874C1810 and Q674B1547. Y594C1389 C1413 238 Heat Controller “Energy Night” logo; contains T874C1844 and Q674F1592. Y594R1425 E-W2 jumper required; system: EM.HT.-Heat-Off-Cool. C1421 249 Obsolete. TRADELINE; contains T874C1877 and Q674B1554. Y594D1347 Replacement has auto changeover; jumper RH-RC. C1439 T874C1869 and Q674C1579. Wiring differences (old=new): Y=Y1; jumper RC-RH and Y1W1; replacement has no SERVICE LED; replacement has fan switching and HEATOFF-COOL system switching. Wiring differences (old=new): Y=Y1; jumper RC-RH; Y1-W; replacement has no SERVICE LED. None Y594D D1016 44 Obsolete. Trane part no. 268-0201-2; contains T874D1082, Q674B1018. T874D1165/ Q674B1018 D1024 72 Trane part no. BAYSTAT010; contains T874D1082, Q674C1009. T874D1165/ Q674C1058 D1032 91 Obsolete. Trane part no. BAYSTAT011; contains T874D1082, Q674G1021. T874D1165/ Q674G1070 D1040 46 Amana part no. P68535-19R; contains T874D1082, Q674B1075. T874D1165/ Q674B1075 D1057 a 55, 66 Obsolete. Trane part no. BAYSTAT007; contains T874D1082, Q674D1008. T874D1165/ Q674D1040 D1149 46 Obsolete. Amana part no. P68535-20C; contains T874D1322, Q674B1075. T874D1165/ Q674B1075 D1156 48 Obsolete. Trane part no. BAYSTAT013; contains T874D1082, Q674B1133. T874D1165/ Q674B1018 D1180 82 York part no. 025-23321-000; contains T874D1504, Q674E1007. T874D1165/ Q674E1049 D1222 166 Obsolete. WeatherKing; contains T874D1009, Q674F1337. T874D1165/ Q674F1022 D1248 82 Obsolete. Reznor part no. 93437; contains T874D1629, Q674E1007. T874D1165/ Q674E1049 D1297 82 Obsolete. ArcoAire part no. 1506753; contains T874D1769, Q674E1346. T874D1165/ Q674E1049 D1305 82 Obsolete. Comfortmaker part no. 1505753; contains T874D1785, Q674E1346. T874D1165/ Q674E1049 D1321 45 Obsolete. Goodman part no. CHT 90-120; contains T874D1843, Q674B1000. T874D1165/ Q674B1034 D1339 82 Obsolete. Nordyne part no. 5471180; contains T874D1009, Q674E1007. T874D1165/ Q674E1049 Both the thermostat and subbase must be replaced. 60-2485—8 88 Replacement has no FILTER LED. Wiring differences (old=new): R=RH; jumper RC-RH; replacement has no EM.HT. or AUX. HT. LEDs. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number Fig. No. Trade Model Replacementa Description Remarks D1347 82 TRADELINE® contains T874D1942, Q674E1403. Y594D1347 D1354 82 SUPER TRADELINE® contains T874D2031 (no cover), Q674E1049, and TG504A with two keys. Y594D1354 D1370 45 Obsolete. Carrier part no. 50QE90022101; contains T874D2049 and Q674B1539. T874D1165/ Q674B1034 Replacement has °F scaleplate. D1388 72 Obsolete. Carrier part no. 50QE90023101; contains T874D2049 and Q674C1520. T874D1165/ Q674C1058 Replacement has °F scaleplate. D1396 184 Obsolete. Carrier part no. 50QE90025101; contains T874D2049 and Q674G1153. T874D1165/ Q674G1070 Replacement has °F scaleplate. 55, 66 Obsolete. Carrier part no. 50QE90024101; contains T874D2049 and Q674D1164. T874D1165/ Q674D1040 Replacement has °F scaleplate. D1404 D1412 82 Obsolete. Carrier “Weathermaker” part no. HH07AT209; taupe color; contains T874D2064 and Q674E1445. T874D1165/ Q674E1049 Replacement is beige color. D1420 82 Obsolete. Carrier “Zone Perfect” part no. HH07AT208; taupe color; contains T874D2072 and Q674E1445. T874D1165/ Q674E1049 Replacement is beige color. D1438 55, 66 Obsolete. Contains T874D2098 and Q674D1008. T874D1165/ Q674D1040 Replacement has 2 setpoint levers. D1446 55, 66 Obsolete. Contains T874D2106 and Q674D1008. T874D1165/ Q674D1040 Replacement has °F scaleplate and 2 setpoint levers. D1453 208 Obsolete. Amana logo; part no. P1217501F; contains T874D2163 and Q674D1172. T874D1165/ Q674D1040 D1461 45 Obsolete. Amana logo; part no. P1217701F; contains T874D2171 and Q674B1562. T874D1942/ Q674B1034 72 Obsolete. Trane part no. BAYSTAT015; contains T874E1040, Q674C1009. T874B1019/ Q674C1058 F1022 44 Obsolete. Contains T874F1031 and 40003440-001 wallplate with installed diode. T874F1015 F1048 72 Obsolete. Reznor part no. 93436; contains T874F1130, Q674C1009. T874F1015/ Q674C1058 F1063 91 Obsolete. Reznor part no. 93435; contains T874F1130, Q674G1005. T874F1015/ Q674G1070 G1013 160 Obsolete. York part no. 2TH11702424; contains T874G1170, Q674J1027. Y594G1567 G1138 160 Obsolete. York part no. 025-22286; contains T874G1196, Q674J1027. Y594G1567 G1153 154 Obsolete. Crispaire part no. HP10-51; contains T874G1089, Q674F1204. Y594G1252 G1161 162 Contains T874G1204, Q674J1043. Y594G1161 G1195 155 Obsolete. Heil Quaker part no. HQ521387HW; contains T874G1246, Q674F1212. Y594G1252 G1229 160 Obsolete. York part no. 6TH11702424; contains T874G1428, Q674J1027. Y594G1567 G1245 155 Obsolete. BDP part no. HH641502; contains T874G1451, Q674F1212. Y594G1252 G1252 155 TRADELINE; contains T874G1246, Q674F1212. Y594G1252 Y594E E1015 Y594F Y594G a Wiring differences (old=new): A=L. Both the thermostat and subbase must be replaced. 89 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number a Fig. No. Trade Model Replacementa Description Remarks G1294 79 Obsolete. LSI; contains T874G1378, Q674C1124. See OEM for replacement. H2 is night setback. G1328 194 Obsolete. Addison part no. 8403-197; contains T874G1543, Q674F1345. Y594G1252 Wiring differences (old=new): Y1=O, X=L, C=X. G1344 194 Obsolete. Heat Controller part no. 7601-110B; contains T874G1469, Q674F1345. Y594G1252 Wiring differences (old=new): Y1=O, X=L, C=X; W1=Y. G1351 160 Obsolete. Luxaire part no. 026-00068-000; contains T874G1568, Q674J1126. Y594G1567 G1369 155 Obsolete. Contains T874G1246, Q674F1212. Y594G1252 G1377 169 Obsolete. Coleman part no. 3600-373; contains T874G1576, Q674F1402. Y594G1633 G1385 155 Obsolete. ArcoAire; contains T874G1592, Q674F1212. Y594G1252 G1393 170 Obsolete. Contains T874R1393, Q674L1454. Y594G1393 G1419 227 TRADELINE; contains T874G1642, Q674F1444. Y594G1419 G1427 177 Obsolete. Mammoth part no. 73034101; contains T874G1659, Q674C1330. See OEM for replacement. G1443 174 Obsolete. American Standard (Trane) part no. ASYSTAT650; contains T874G1675, Q674J1142. Y594G1161 G1476 227 TRADELINE; same as Y594G1419 except Premier White® color; contains T874G1741, Q674F1477. Y594G1476 G1492 211 Trol-A-Temp; contains T874G1758, Q674F1485. G1500 216 Obsolete. Comfortmaker part no. 1505756; contains T874G1774, Q674J1175. See OEM for replacement. G1518 216 Obsolete. ArcoAire part no. 1506756; contains T874G1782, Q674J1175. See OEM for replacement. G1526 167 TRADELINE; contains T874G1626, Q674F1436. None G1534 227 TRADELINE; °C; white; Australia; contains T874G1824, Q674F1477. None G1542 231 Obsolete. Intertherm part no. 9129290; contains T874G1832, Q674F1519. Y594G1252 Cooling changeover only. G1559 231 Obsolete. Miller part no. 9129310; contains T874G1840, Q674F1519. Y594G1252 Cooling changeover only. G1567 160 TRADELINE; contains T874G1865, Q674J1209. Y594G1567 G1575 160 Obsolete. TRADELINE; same as Y594G1567 except Premier White® color; contains T874G1873, Q674J1225; direct replacement for York 2TH11702424 (Y594G1013 contains T874G1170/ Q674J1027) and 6TH11702424 (Y594G1229 contains T874G1428/Q674J1027). Y594G1567 Replacement is beige. G1583 229 Obsolete. Lennox Canada part no. 97E78; contains T874G1857, Q674F1535. Y594G1161 Wiring differences (old=new): E=X2, C=B, L=F. G1591 243 Obsolete. Amana part no. 10636701; contains T874G1899 and Q674F1550. Y594G1633 G1609 155 Obsolete. Econar; contains T874G1915 and Q674F1212. Y594G1252 Both the thermostat and subbase must be replaced. 60-2485—8 90 None H2 is night setback. See Trol-A-Temp for replacement. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Model Number G1617 Fig. No. 73 Trade Model Replacementa Description Obsolete. Carrier part no. 50QE90020101; contains T874G1949 and Q674C1504. Y594H1012 a Remarks Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; R-L jumper required; no night setback. T8600D2028 Wiring differences (old=new): (programmable) Y1=O, Y2=Y, L=R; W-Y jumper required; night setback. G1625 160 York Canada part no. 2TH11702524; contains T874G1964 and Q674J1266. Y594G1567a G1633 169 TRADELINE; contains T874G1972 and Q674F1584; direct replacement for Y594G1377 (T874G1576/Q674F1402) Evcon/Coleman part no. 3600-373. Y594G1633a G1641 169 Obsolete. Amana part no. 10636703; contains T874G1980 and Q674F1600. Y594G1633 G1658 155 Obsolete. Tempstar “Inter-City Products” part no. 1149910; contains T874G1998 and Q674F1212. Y594G1252 G1666 103 Obsolete. TRADELINE; manual changeover; contains T874G2004 and Q674L1892; direct replacement for Y507J1011 (T874G1055/ Q674L1041) Carrier part no. 99TZ90041106 (HH07AT171/HH93AZ1750). Y594G1674 G1674 161 TRADELINE; automatic changeover; contains T874G2004 and Q674J1274; direct replacement Y507J1003 (T874G1055/Q674J1035) Carrier part no. 99TZ90040106 (HH07AT171/HH93AZ173). Y594G1674 G1716 155 WaterFurnace logo; part no. TA21H03; contains T874G2046 and Q674F1667. Y594G1716 H1004 79 Obsolete. LSI part no. 73033901; contains T874H1039 and Q674C1124. T8600D2028 H1012 164 Contains T874H1062 and Q674C1249; replaces T874H1005/Q674C1041. Y594H1012 H1020 177 Obsolete. Mammoth part no. 71117101; contains T874H1096 and Q674C1330. Y594H1012 Wiring differences (old=new): R1=R, R2=L; use jumper provided. H1038 74 Obsolete. Carrier part no. 50QE90019101; contains T874H1161 and Q674C1496. Y594H1012a Wiring differences (old=new): X1=O, Y2=Y; L-R jumper required. H1046 172 Obsolete. Carrier part no. 50QE90026101; contains T874H1153 and Q674B1406. T874A1130/ Q674B1075a Wiring differences (old=new): Y=Y1; W1-Y1 jumper required; replacement has no LEDs. H1053 173 Obsolete. Carrier part no. 50QE90027101; contains T874H1153 and Q674C1322. Y594H1012a Wiring differences (old=new): Z=X. 241 Obsolete. TRADELINE; manual changeover; contains T874J1069 and Q674L1900; direct replacement for T874J1002 or T874A1028 used with Q674L1074 or Q674L1637 (HH07AT175 or HH07AT165 used with HH93AZ186 or HH93AZ195). (Recontrol) T8511G1021 Replacement has °F scaleplate. Wiring differences (old=new): W3=W2. Replacement has auto changeover. Y594H H2 is night setback. Y594J J1001 a Both the thermostat and subbase must be replaced. 91 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Trade Model Replacementa Model Number Fig. No. J1019 244 Obsolete. TRADELINE; automatic changeover; contains T874J1069 and Q674J1282; direct replacement for T874J1002 or T874J1028 used with Q674J1068 or Q674J1159 (HH07AT175 or HH07AT165 used with HH93AZ183 or HH93AZ196). (Recontrol) T8511G1021 N1007 178 Obsolete. Williamson part no. 75-189; contains T874N1008 and Q674F1196. T874N1016/ Q674F1196 N1015 179 Obsolete. Contains T874N1040 and Q674F1261. Y594G1419a N1023 178 Obsolete. Intertherm part no. 9111882; contains T874N1057 and Q674F1220. T874N1016/ Q674F1220 N1031 178 Obsolete. Nordyne “Miller” part no. 9122240; contains T874N1065 and Q674F1220. T874N1016/ Q674F1220 97 Obsolete. Carrier part no. 50QE90021101; contains T874P1055 and Q674C1512. T8600D2028 R1011 120 Obsolete. York part no. 2TH11702224; contains T874R1046 and Q674L1272. Y594R1664 R1029 47 Obsolete. Bryant; contains T874R1004 and Q674B1042. Y594R1243 Wiring differences (old=new): W1=W2. R1037 122 Obsolete. Fedders part no. 88-58-00540-001; contains T874R1269 and Q674L1066. Y594R1615 Wiring differences (old=new): K=E, C=X, W1=B, Z=L. R1102 120 Obsolete. York part no. 025-22285-000; contains T874R1145 and Q674L1272. Y594R1664 R1110 108 Obsolete. Heil Quaker part no. HQ712004HW; contains T874R1137 and Q674L1132. Y594R1292 R1128 116 Obsolete. Crispaire part no. HP9-51; contains T874R1111 and Q674L1215. Y594R1243 R1136 109 Obsolete. Contains T874R1053 and Q674L1140. Y594R1763 R1151 120 Obsolete. York part no. 2TH11702324; contains T874R1251, Q674L1272 and C815A1039. Y594R1672 R1185 201 Obsolete. Intertherm part no. 9111871; contains T874R1202 and Q674L1264. Y594R1672 R1193 120 Obsolete. York part no. 6TH11702224; contains T874R1327 and Q674L1272. Y594R1664 R1201 106 Obsolete. BDP part no. HH641501; contains T874R1335 and Q674L1405. Y594R1243 R1219 133 Obsolete. Fedders part no. 88-58-00560-001; contains T874R1343 and Q674L1413. Y594R1425 R1235 125 Obsolete. Coleman part no. 3600-368; contains T874R1368 and Q674L1421. Y594R1797 R1243 115 TRADELINE; contains T874R1152 and Q674L1207. Y594R1243 R1250 128 Obsolete. Williamson part no. 75-191; contains T874R1392 and Q674L1447. Y594R1425 R1284 136 Obsolete. Trane part no. BAYSTAT339; contains T874R1426 and Q674L1496. Y594R1763 Description Remarks Y594N Wiring differences (old=new): L=X2, Y=Y1. Y594P P1005 Wiring differences (old=new): Y=Y1, W=O; Y1-W1 jumper required. Y594R a Both the thermostat and subbase must be replaced. 60-2485—8 92 Wiring differences (old=new): A=L. Wiring differences (old=new): W2=W, X=B, Z=no connection, K=X, W1=H. Wiring differences (old=new): K=E, C=X, Z=L; remove factory installed jumper. Wiring differences (old=new): A=L. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. a Trade Model Replacementa Model Number Fig. No. R1292 108 Contains T874R1467 and Q674L1512; replaces Y594R1110 (T874R1137/Q674L1132). Y594R1292 R1300 123 Contains T874R1475 and Q674L1520. Y594R1300 R1318 130 Obsolete. Comfortmaker part no. 1505721; contains T874R1483, Q674L1538 and C815A1005. Y594R1763 R1326 137 Obsolete. SUPER TRADELINE; contains T874R1491 and Q674L1553. Y594R1615 R1334 47 Obsolete. Slant Fin; contains T874R1509 and Q674B1042. Y594R1243 Wiring differences (old=new): W1=W2. R1342 130 Obsolete. ArcoAire part no. 1506721; contains T874R1517, Q674L1538 and C815A1005. Y594R1763 Wiring differences (old=new): W1=W, E=X2, X=F, C=B. R1359 113 Obsolete. ArcoAire part no. A02074; contains T874R1525 and Q674L1181. Y594R1243 Wiring differences (old=new): X1=X. R1375 130 Obsolete. Contains T874R1566, Q674L1538 and C815A1005. Y594R1763 Wiring differences (old=new): W1=W, E=X2, X=F, C=B. R1383 132 Obsolete. Comfortmaker part no. 1505739; contains T874R1574 and Q674L1538. Y594R1243 Wiring differences (old=new): W=W2, C=X, X=L. R1391 132 Obsolete. ArcoAire part no. 1506739; contains T874R1582 and Q674L1538. Y594R1243 Wiring differences (old=new): W=W2, C=X, X=L. R1409 119 Obsolete. Intertherm part no. 6244630; contains T874R1608 and Q674L1264. Y594R1763 Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. R1417 113 Obsolete. Comfortmaker part no. 1505-735; contains T874R1301 and Q674L1181. Y594R1243 Wiring differences (old=new): X1=X. R1425 168 SUPER TRADELINE; contains T874R1616 and Q674L1587. Y594R1425 R1433 200 Obsolete. Miller part no. 9115900; contains T874R1624 and Q674L1595. Y594R1243 R1441 136 Obsolete. American Standard (Trane) part no. ASYSTAT651; contains T874R1657 and Q674L1611. Y594R1763 R1466 108 Heil Quaker part no. 1060321; model no. HAXB004TW01; contains T874R1673 and Q674L1132. Y594R1292 R1482 119 Obsolete. Nordyne “Miller” part no. 9122230; contains T874R1699 and Q674L1264. Y594R1763 R1490 209 Trol-A-Temp; contains T874R1707 and Q674L1678. None See Trol-A-Temp for replacement. R1508 209 Trol-A-Temp; contains T874R1715 and Q674L1686. None See Trol-A-Temp for replacement. R1516 132 Obsolete. Snyder General part no. 654958B07; contains T874R1723, Q674L1702 and C815A1005. Y594R1763 R1524 108 Obsolete. Inter-City Products part no. HQ1147925HW; contains T874R1731 and Q674L1132. Y594R1292 R1532 108 Heil Quaker part no. 1060322; model no. TAXB004TW01; contains T874R1749 and Q674L1132. Y594R1292 R1607 108 Obsolete. Keeprite THPC; contains T874R1814 and Q674L1132. Y594R1292 Description Remarks Wiring differences (old=new): W1=W, E=X2, X=F, C=B. Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O. Wiring differences (old=new): W1=W, C=B, X=X2. Both the thermostat and subbase must be replaced. 93 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. a Trade Model Replacementa Model Number Fig. No. R1615 230 TRADELINE; contains T874R1822 and Q674L1710; replaces Y594R1326 (T874R1491/ Q674L1553). Y594R1615 R1623 134 Obsolete. Rheem Universal Parts part no. 4120796-46; contains T874R1558 and Q674L1504. Y594R1300 R1631 134 Rheem part no. 41-20796-29; contains T874R1442 and Q674L1504. Y594R1300 R1649 134 Ruud part no. 41-20796-33; contains T874R1434 and Q674L1504. Y594R1300 R1656 134 Obsolete. WeatherKing part no. 41-20796-64; contains T874R1830 and Q674L1504. Y594R1300 R1664 120 TRADELINE; contains T874R1871 and Q674L1736; direct replacement for York 2TH11702224 (Y594R1011 contains T874R1046/ Q674L1272). Y594R1664 R1672 120 TRADELINE; contains T874R1889, Q674L1736 and C815A1054; direct replacement for York 2TH11702324 (Y594R1151 contains T874R1251/ Q674L1272/C815A1039) and 6TH11702224 (Y594R1193 contains T874R1327/Q674L1272). Y594R1672 R1680 230 TRADELINE; same as Y594R1615 except Premier White® color; contains T874R1897 and Q674L1751; direct replacement for Y594R1326 (T874R1491/Q674L1553). Y594R1680 R1698 120 Obsolete. TRADELINE; Premier White® color; contains T874R1905, Q674L1777 and C815A1054. Y594R1672 Replacement is beige. R1706 120 Obsolete. TRADELINE; same as Y594R1664 except Premier White® color; contains T874R1913 and Q674L1777; direct replacement for Y594R1011 (T874R1046/Q674L1272) York part no. 2TH11702224. Y594R1664 Replacement is beige. R1714 228 Obsolete. Lennox part no. 97E79; Canada; Premier White® color; contains T874R1855 and Q674L1728. Y594R1763 Wiring differences (old=new): Y1=Y, L=F, W1=W, E=W2, C=B. R1722 115 Obsolete. Econar; contains T874R1921 and Q674L1207. Y594R1243a R1748 197 American Standard (Trane) part no. ASYSTAT651A; contains T874R1939 and Q674L1801. Y594R1763a R1755 168 Obsolete. Inter-City Products part no. HQ1149376HW; contains T874R1947 and Q674L1819. Y594R1425a R1763 197 TRADELINE: contains T874R1954 and Q674L1827; direct replacement for Y594R1136 (T874R1053/Q674L1140), Y594R1748 (T874R1939/Q674L1801) Trane part no. ASYSTAT651A, Y594R1441 (T874R1657/ Q674L1611) Trane part no. ASYSTAT651. Y594R1763 R1771 115 Obsolete. Consolidated Industries part no. 9036100; contains T874R1962 and Q674L1843. Y594R1680a Includes CHECK LED. R1789 120 York Canada part no. 2TH11701524; contains T874R1970 and Q674L1850. Y594R1672a Replacement has °F scaleplate. Description Both the thermostat and subbase must be replaced. 60-2485—8 94 Remarks T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10. Y594 Cross Reference. Trade Model Replacementa Model Number Fig. No. R1797 125 TRADELINE; contains T874R1988 and Q674L1868; direct replacement for Y594R1235 (T874R1368/Q674L1421) Evcon/Coleman part no. 3600-368). Y594R1797 R1805 245 Obsolete. Amana part no. 10636702; contains T874R2002 and Q674L1876. Y594R1797 Wiring differences (old=new): C/X=X. R1813 245 Obsolete. Amana part no. 10636704; contains T874R2010 and Q674L1884. Y594R1797 Wiring differences (old=new): C/X=X, W3=W2. R1821 125 Obsolete. York logo; part no. 2TH11703424A; contains T874R2028 and Q674L1918. Y594R1797 R1839 134 Rudd logo; part no. 41-20796-48; contains T874R2036 and Q674L1504. See OEM for replacement. R1854 123 Obsolete. Rheem logo; part no. 41-20796-47; contains T874R1996 and Q674L1504. Y594R1300 W1014 54 Contains T874W1015, Q674B1216 and C815A1005. Y594W1014 W1022 140 Obsolete. Rheem part no. 41-20797-19; contains T874W1031, Q674L1546 and C815A1005. T8611M2025. W1030 68 Obsolete. Inter-City Products part no. 1072350; contains T874W1072, Q674L1835 and C815A1005 Outdoor Thermistor. W1055 247 Obsolete. Addison logo; part no. 843-277; contains T874W1106, Q674L1934 and C815A1005. T8611M2025 Y1004 210 Obsolete. Mammoth part no. 71117301; contains T874Y1005 and Q674E1353. See OEM for replacement. Y1012 248 Obsolete. WaterFurnace logo; part no. TA21H03; contains T874Y1013 and Q674F1675. Description Remarks a Y594W T8611M2025 Includes night setback. (programmable) Y594Y a Both the thermostat and subbase must be replaced. 95 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES WIRING DIAGRAMS SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 RH HEAT RELAY 1 W1 1 FAN SWITCH H1 FALL HEAT RELAY 2 AUTO W2 H1 ANTICIPATOR HEAT CHANGEOVER VALVE ON H2 2 6 H2 ANTICIPATOR FALL SYSTEM SWITCH COOL CHANGEOVER VALVE O 8 FAN RELAY HEAT G C1 RISE NOTE: Model ing No. T874A T874B T874C T874D T874E T874D B 4 OFF 9 Heating CoolBulbs H1 H1 H1,H2 H1,H2 Bulbs C1 C1,C2 C1 C1,C2 C1,C2 H1,H2 COMPRESSOR CONTACTOR 2 COOL Y2 COMPRESSOR CONTACTOR 1 10 C1 ANTICIPATOR Y1 C2 ANTICIPATOR L2 11 RISE L1 (HOT) RC C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. 1 M2903 Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 RH HEAT RELAY 1 3 W1 1 FAN SWITCH H1 FALL 1 HEAT RELAY 2 AUTO W2 H1 ANTICIPATOR HEAT CHANGEOVER VALVE ON B 4 X1 H2 6 FALL H2 ANTICIPATOR SYSTEM SWITCH O COOL CHANGEOVER VALVE 8 HEAT C1 RISE G OFF 9 FAN RELAY 2 COOL Y2 COMPRESSOR CONTACTOR 2 10 C1 ANTICIPATOR Y1 C2 ANTICIPATOR RISE 11 C2 RC 1 2 COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. JUMPER RH, RC FOR SINGLE TRANSFORMER. 3 OPTIONAL LED ON SOME MODELS. Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications. 60-2485—8 96 L2 L1 (HOT) 1 M933C T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE HEAT RELAY 1 W1 1 FAN SWITCH H1 FALL HEAT RELAY 2 AUTO W2 H1 ANTICIPATOR ON HEAT CHANGEOVER VALVE B 4 H2 L1 (HOT) L2 1 R 6 H2 ANTICIPATOR FALL SYSTEM SWITCH O COOL CHANGEOVER VALVE 8 HEAT C1 RISE OFF G 9 COOL FAN RELAY Y2 10 C1 ANTICIPATOR C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 Y1 11 COMPRESSOR CONTACTOR 1 C2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2904 Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications. . SUBBASE THERMOSTAT SYSTEM COMPONENTS O 1 H1/C1 ANTICIPATOR FAN SWITCH COOL CHANGEOVER VALVE AUTO G 2 H1 C1 ON FAN RELAY FALL 3 L1 (HOT) R 4 L2 SYSTEM SWITCH 1 HEAT 5 W1 OFF AUX. HT. RELAY COOL H2 6 FALL Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M2906 Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications. 97 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 (HOT) L2 1 HEAT RELAY 1 W1 1 H1 FAN SWITCH FALL FAN RELAY G AUTO H1 ANTICIPATOR ON EXTERNAL FAN SWITCH 4 RC H2 H2 ANTICIPATOR FALL HEAT RELAY 2 6 W2 8 HEAT CHANGEOVER VALVE C1 RISE 9 B SYSTEM SWITCH L2 RH HEAT 10 OFF C1 ANTICIPATOR COOL C2 ANTICIPATOR RISE 2 X1 L1 (HOT) 1 FILTER LED (RED) O COOL CHANGEOVER VALVE 11 C2 Y1 COMPRESSOR CONTACTOR 1 1 2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y2 COMPRESSOR CONTACTOR 2 CLOGGED FILTER, SERVICE SWITCH. Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications. 60-2485—8 98 M2905 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 1 W1 H2 FAN SWITCH HEAT LED (RED) FALL AUTO BLOWER RELAY G 4 ON H2 ANTICIPATOR L1 (HOT) L2 1 R 6 HEAT RELAY 2 FALL H1 W2 SYSTEM SWITCH 8 C1 ANTICIPATOR HEAT 9 T OFF COOL LED (YELLOW) COOL C1 1 Y1 10 RISE COMPRESSOR CONTACTOR LO SPEED LED (GREEN) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L HSII CONTROL PANEL C HI SPEED LED (GREEN L1 (HOT) L2 H M5945 Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS O 1 H1 ANTICIPATOR 2 FALL H1 COOL CHANGEOVER VALVE FAN SWITCH Y AUTO 4 COMPRESSOR CONTRACTOR ON FALL H2 G H2 ANTICIPATOR AUX. HT. RELAY 6 SYSTEM SWITCH 8 CO FAN RELAY W2 L2 RISE HEAT 9 C1 RISE OFF C1 ANTICIPATOR R 1 L1 (HOT) COOL 10 M8000 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications. 99 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 FALL W1 H1 1 H1 ANTICIPATOR FAN SWITCH FAN RELAY G 3 AUTO L1 (HOT) 1 L2 ON RC 4 2 HEAT RELAY 2 W2 6 FALL HEAT CHANGEOVER VALVE H2 ANTICIPATOR H2 B 8 3 SYSTEM SWITCH RH C1 HEAT RISE 9 COOL CHANGEOVER VALVE O OFF 3 COOL C1 ANTICIPATOR COMPRESSOR CONTACTOR 1 10 Y1 C2 ANTICIPATOR RISE COMPRESSOR CONTACTOR 2 11 Y2 C2 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. 3 B, O TERMINALS ON SOME MODELS. L1 L2 (HOT) M5944 Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications. SUBBASE THERMOSTAT H1 ANTICIPATOR H1 1 SYSTEM COMPONENTS W1 FAN SWITCH HEAT RELAY 1 AUTO FAN RELAY G FALL ON L1 (HOT) RC 3 4 1 5 W3 6 W2 H2 FALL L2 F H2 ANTICIPATOR SYSTEM SWITCH 2 HEAT RELAY 2 RH HEAT B OFF 8 COOL C1 RISE 9 O C1 ANTICIPATOR Y1 COMPRESSOR CONTACTOR 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER. W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION. 3 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications. 60-2485—8 100 M5999 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT 1 H1 ANTICIPATOR HEAT RELAY 1 FAN SWITCH W1 AUTO FALL HEAT RELAY 2 H1 ON 4 W2 H2 6 FALL H2 ANTICIPATOR 8 L1 (HOT) R SYSTEM SWITCH L2 HEAT RISE C1 1 OFF 9 G COOL FAN RELAY 10 Y2 C1 ANTICIPATOR COMPRESSOR CONTACTOR 2 C2 ANTICIPATOR 11 Y1 C2 RISE 1 COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3202A Fig. 53. Schematic and hookup of T874D with Q674B. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS 1 1 H1 ANTICIPATOR FALL C815A THERMISTOR H1 H2 ANTICIPATOR 2 FAN SWITCH FALL L1 (HOT) R L2 T 3 AUTO H3 4 H3 ANTICIPATOR W1 HEAT RELAY 1 ON W2 HEAT RELAY 2 5 FALL H2 6 RESET HEATER SYSTEM SWITCH HEAT RELAY 3 B HEAT CHANGEOVER VALVE HEAT RISE 8 C1 W3 OFF G FAN RELAY COOL C1 ANTICIPATOR O 10 COOL CHANGEOVER VALVE C2 ANTICIPATOR RISE 11 Y2 COMPRESSOR CONTACTOR 2 C2 1 Y1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 M3674 Fig. 54. Schematic and hookup of T874W with Q674B. Used in standard applications. 101 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES H1 L1 (HOT) L2 RH FALL 3 B 1 H1 ANTICIPATOR HEAT RELAY 1 NO FAN SWITCH 3 H2 ANTICIPATOR 1 W1 4 5 6 FALL SYSTEM COMPONENTS SUBBASE THERMOSTAT HEAT RELAY 2 W2 H2 2 8 NO SYSTEM SWITCH C1 RISE COMPRESSOR CONTACTOR 2 Y2 9 COMPRESSOR CONTACTOR 1 C1 ANTICIPATOR Y1 10 C2 L2 C2 ANTICIPATOR RC L1 (HOT) RISE 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RC, RH FOR SINGLE TRANSFORMER. 3 B AND 5 TERMINALS AVAILABLE ON SOME MODELS. M3667A Fig. 55. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications. SYSTEM COMPONENTS SUBBASE RESET 1 FALL FAN SWITCH H1 X RESET LED (RED) FAN RELAY AUTO G H1 ANTICIPATOR ON 4 R AUX. HT. RELAY H2 ANTICIPATOR W2 6 H2 SYSTEM SWITCH FALL 8 B HEAT OFF 9 RISE B RELAY O COOL C1 ANTICIPATOR C1 L1 (HOT) L2 1 O RELAY Y2 10 COMPRESSOR CONTACTOR 1 11 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 56. Schematic and hookup of T874C with Q674B. Used in standard applications. 60-2485—8 102 M5975 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS Y FALL FAN SWITCH COMPRESSOR CONTACTOR AUTO 1 FAN RELAY G L1 (HOT) ON R 2 H2 CLOSED-DAY OPEN-NITE H1 ANTICIPATOR 3 1 B L 4 SYSTEM SWITCH 5 OVERRIDE HEAT 6 CO L2 B RELAY S JUMPER OFF RISE H1 2 COOL 8 P COOL CHANGEOVER VALVE W 9 RISE C1 C1 ANTICIPATOR T 10 1 POWERSUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. M8004 Fig. 57. Schematic and hookup of T874P with Q674B. Used in heat pump applications. THERMOSTAT H1 ANTICIPATOR H1 SUBBASE 2 Y 3 FALL H2 ANTICIPATOR ECONOMIZER PACKAGE NO FAN SWITCH 4 FALL SYSTEM COMPONENTS 6 RH Y O O W W2 H2 8 RISE NO SYSTEM SWITCH B 9 C1 ANTICIPATOR CO 10 RC O CONTROL PANEL C1 M3722 RISE Fig. 58. Schematic and hookup of T874G with Q674D. Used in standard applications. 103 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR SUBBASE SYSTEM COMPONENTS 1 W1 SYSTEM SWITCH HEAT HEAT RELAY 1 OFF 4 B 1 COOL FALL FAN SWITCH 8 G1 RISE C1 L1 (HOT) L2 R H1 LO 9 MED C1 ANTICIPATOR L1 G2 HIGH 10 L2 K1 RELAY K1 K1 K2 RELAY K2 O ON HI K2 K2 MED LO Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 3 SPEED FAN SCHEMATIC M3729 Fig. 59. Schematic and hookup of T874A with Q674Q. Used in fan coil applications. SUBBASE THERMOSTAT H1 ANTICIPATOR 1 SYSTEM COMPONENTS W1 FAN SWITCH AUTO FALL L1 (HOT) L2 1 COOL RELAY CONTACT FAN RELAY G ON H1 4 R 6 FALL H2 ANTICIPATOR H2 SYSTEM SWITCH ELEC. HT. RELAY W2 EVAP CHANGEOVER VALVE 8 COOL OFF RISE 9 B COMPRESSOR CONTACTOR HEAT C1 Y1 C1 ANTICIPATOR EVAPORATOR RELAY 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y2 Fig. 60. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications. 60-2485—8 104 M2863 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE COMPRESSOR CONTACTOR FALL Y1 H1 1 FAN RELAY H1 ANTICIPATOR FAN SWITCH G 4 AUTO 1 ON FALL H2 ANTICIPATOR L1 (HOT) L2 R 6 H2 ELEC. HT. RELAY W2 RISE 8 EVAPORATOR RELAY SYSTEM SWITCH C1 Y2 EVAP. 9 COOL CHANGEOVER RELAY OFF C1 ANTICIPATOR 1 O HEAT 10 M2862 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 61. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS FAN SWITCH FAN RELAY AUTO G FALL ON H2 1 W2 H2 ANTICIPATOR AUX. HT. RELAY R 4 YELLOW C FALL H1 SYSTEM SWITCH WOOD/COAL RELAY GREEN 8 W1 HEAT COMPRESSOR CONTACTOR 9 OFF X2 COOL H1 ANTICIPATOR X1 1 L2 EXTERNAL COOLING THERMOSTAT (SUCH AS T87 F) 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y R L1 (HOT) 1 M3723A Fig. 62. Schematic and hookup of T874F with Q674B. Used in wood/coal applications. 105 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H2 SUBBASE SYSTEM COMPONENTS AUX. HT. RELAY NO FAN SWITCH FALL 1 W2 1 H2 ANTICIPATOR L1 (HOT) R NO SYSTEM SWITCH 4 FALL H1 YELLOW L2 C HEAT/COOL SWITCH GREEN 8 W1 WOOD/COAL RELAY 9 H1 ANTICIPATOR 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 M3725 Fig. 63. Schematic and hookup of T874F with Q674D. Used in wood/coal applications. THERMOSTAT SYSTEM COMPONENT SUBBASE 1 HEAT RELAY 1 H1 ANTICIPATOR H1 W1 B SYSTEM SWITCH HEAT 2 B RELAY OFF FALL 1 COOL 2 3 L1 (HOT) L2 R 4 C1 ANTICIPATOR K1 RELAY FAN SWITCH 5 L2 G1 MED K2 RELAY HIGH C1 K1 K1 G2 ON RISE L1 LO O RELAY K2 O K2 K2 COMPRESSOR CONTACTOR Y1 LO HI MED 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SINGLE SETPOINT LEVER AND BIMETAL. 3-SPEED FAN SCHEMATIC M8005 Fig. 64. Schematic and hookup of T874A with Q674Q. Used in fan coil applications. 60-2485—8 106 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 W1 NO. 1 HEAT RELAY AUTO FAN SWITCH ON W2 H1 ANTICIPATOR B 4 HEAT DAMPER 6 FALL H1 L1 (HOT) L2 RH 8 L1 (HOT) L2 1 RC 9 RISE C1 COOL DAMPER SYSTEM SWITCH HEAT O OFF G 10 FAN RELAY C1 ANTICIPATOR COOL 11 Y2 NO. 1 COMP. RELAY Y1 FILTER LED (RED) X1 SERVICE LED (YELLOW) X2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 M5976 Fig. 65. Schematic and hookup of T874A with Q674B. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS HEAT RELAY 1 H1 ANTICIPATOR 1 W1 NO FAN SWITCH HEAT RELAY 2 4 FALL H1 W2 5 H2 L1 (HOT) L2 1 RH 6 FALL NO SYSTEM SWITCH H2 ANTICIPATOR 8 9 RC 10 Y2 11 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) L2 1 M7011 Fig. 66. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications. 107 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS 1 X FAN RELAY FAN SWITCH 2 H1 C1 G AUTO H1/C1 ANTICIPATOR L1 (HOT) ON FALL 3 R L2 1 4 HEAT CHANGEOVER VALVE 5 SYSTEM SWITCH B FALL W2 H2 HEAT AUX. HT. RELAY 6 OFF COOL COMPRESSOR CONTACTOR Y 1 M5998 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 67. Schematic and hookup of T874R with Q674B. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS 1 Y H1 ANTICIPATOR 3 H2 COMPRESSOR CONTACTOR 2 G FALL 3 FAN SWITCH FAN RELAY C 4 CLOSED-DAY OPEN-NITE AUTO 5 ON RISE CO H1 SYSTEM SWITCH RISE L1 (HOT) R OVERRIDE LED (RED) 6 8 C1 L2 SERVICE LED (RED) 1 B B RELAY L OVERRIDE X 9 HEAT S OFF C1 ANTICIPATOR 10 COOL JUMPER 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. 3 H2 MAKE OFFEST 8˚ F BELOW H1 MAKE. COMPRESSOR FAULT P 2 COOL CHANGEOVER VALVE W T M101A Fig. 68. Schematic and hookup of T874P with Q674B. Used in heat pump applications. 60-2485—8 108 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH LO AUTO HI Z RELAY Z CONT. G SYSTEM SWITCH FAN RELAY OFF COOL RISE R 8 C1 L1 (HOT) L2 1 9 COOL RELAY 10 Y C1 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M107A Fig. 69. Schematic and hookup of T874V with Q674R. Used in fan coil applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS 1 SERVICE LED (RED) NO FAN SWITCH H1 FALL S COMPRESSOR FAULT 4 6 W2 SYSTEM SWITCH H2 FALL 8 9 AUX. HT. RELAY 1 HEAT L2 COOL R L1 (HOT) Y H1 FALL 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M1402A Fig. 70. Schematic and hookup of T874C with Q674S. Used in heat pump applications. 109 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT 1 H1 ANTICIPATOR FAN SWITCH AUTO HEAT RELAY 1 3 ON FALL L1 (HOT) L2 RH CHECK 1 W1 H1 HEAT RELAY 2 4 W2 H2 6 FALL H2 ANTICIPATOR SYSTEM SWITCH X1 8 HEAT RISE G AUTO C1 9 FAN RELAY 2 COOL 10 Y2 C1 ANTICIPATOR COMPRESSOR CONTACTOR 2 Y1 C2 ANTICIPATOR 11 C2 RISE RC 1 2 COMPRESSOR CONTACTOR 1 L1 (HOT) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. JUMPER RH, RC FOR SINGLE TRANSFORMER. 3 L2 1 OPTIONAL LED ON SOME MODELS. M932B Fig. 71. Schematic and hookup of T874A-D with Q674A. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 RH H1 ANTICIPATOR 1 FAN SWITCH H1 2 4 1 HEAT RELAY 1 AUTO FALL W1 W2 ON HEAT RELAY 2 B 6 HEAT DAMPER 3 H2 ANTICIPATOR O H2 FALL COOL DAMPER 8 RISE SYSTEM SWITCH G OFF FAN RELAY C1 9 AUTO Y2 C1 ANTICIPATOR 10 COMPRESSOR CONTACTOR 2 Y1 C2 ANTICIPATOR 11 C2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 2 RC 1 L2 L1 (HOT) 2 JUMPER TERMINALS RC-RH FOR SINGLE SYSTEM TRANSFORMER ONLY. M5122A 3 B,O TERMINALS ON SOME MODELS. Fig. 72. Schematic and hookup of T874D,E,F with Q674C. Used in standard applications. 60-2485—8 110 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS H ANTICIPATOR Y1 2 H1 FALL REVERSING VALVE RELAY 3 Y2 COMPRESSOR CONTACTOR FAN SWITCH 4 AUTO SETBACK G ON FALL FAN RELAY 6 8 CO L2 SYSTEM SWITCH 9 OPEN-NIGHT CLOSED-DAY OFF RISE 1 L1 (HOT) R 10 AUTO SETBACK RELAY C ANTICIPATOR C1 L RISE 1 M7008 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 73. Schematic and hookup of T874G with Q674C. Used in heat pump applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE 2 H1 ANTICIPATOR FALL Y1 COOL CHANGEOVER VALVE 3 H1 FAN SWITCH 4 FAN RELAY AUTO G ON R 8 Y2 SYSTEM SWITCH OFF COMPRESSOR CONTACTOR B RISE C1 ANTICIPATOR 9 AUTO CO 10 O 2 RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SERVICE LED ON SELECT MODELS. L2 L1 (HOT) 1 X SERVICE LED (YELLOW) COMPRESSOR FAULT C M3680A Fig. 74. Schematic and hookup of T874H with Q674C. Used in heat pump applications. 111 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE 1 H1 ANTICIPATOR W1 SYSTEM SWITCH OFF FILTER LED (YELLOW) HEAT RELAY 3 X AUTO 4 8 A SERVICE LED (RED) FAN SWITCH H1 FALL FAN RELAY AUTO 1 G ON L1 (HOT) L2 R 2 RISE 9 O C1 ANTICIPATOR C1 MOMENTARY CIRCUIT O 10 Y COMPRESSOR CONTACTOR 11 T EXTERNAL TEMP. READOUT THERMISTOR 12 T 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 3 FILTER LED ON SELECT MODELS. M5731 Fig. 75. Schematic and hookup of T874A with Q674C. Used in standard applications. SUBBASE THERMOSTAT H1 ANTICIPATOR 1 SYSTEM COMPONENTS W1 FAN SWITCH HEAT RELAY 1 AUTO FALL H1 4 FALL HEAT RELAY 2 W2 HEAT CHANGEOVER VALVE ON B L2 1 L1 (HOT) RH 6 H2 ANTICIPATOR H2 L1 (HOT) RC 8 C1 O SYSTEM SWITCH RISE 9 OFF 10 AUTO COOL CHANGEOVER VALVE L2 1 G FAN RELAY Y2 C1 ANTICIPATOR RISE 11 C2 3 C2 ANTICIPATOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FOR T874C, DELETE C2. FILTER LED (YEL) SERVICE LED (RED) Y1 COMPRESSOR CONTACTOR 2 COMPRESSOR CONTACTOR 1 X A 3 FILTER LED ON SELECT MODELS. Fig. 76. Schematic and hookup of T874A-D with Q674C. Used in standard applications. 60-2485—8 112 M7025 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 1 FALL FAN SWITCH SYSTEM COMPONENTS RESET LED (RED) X1 FAN RELAY AUTO CO G 3 ON FALL H2 L1 (HOT) L2 1 RH 4 2 FALL 6 HEAT CHANGEOVER VALVE H1 H1 ANTICIPATOR W1 HEAT RELAY 2 W3 8 HEAT RELAY 1 RISE SYSTEM SWITCH C1 9 W2 "B" RELAY OFF B C1 ANTICIPATOR 10 1 2 AUTO L1 (HOT) 1 L2 RC POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. "O" RELAY O JUMPER RH AND RC FOR SINGLE TRANSFORMER SYSTEM. COMPRESSOR CONTACTOR Y1 M4729 Fig. 77. Schematic and hookup of T874K with Q674C. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS Y 1 FALL H2 FAN SWITCH COMPRESSOR CONTACTOR AUTO 2 H1 ANTICIPATOR G ON FAN RELAY C 3 4 SETBACK CONTACT 5 6 CO SYSTEM SWITCH 8 1 HEAT CHANGEOVER VALVE AUTO RISE L2 B OVERRIDE H1 L1 (HOT) R L OFF C1 9 S JUMPER 2 10 P REVERSING VALVE C1 ANTICIPATOR RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. W M7026 Fig. 78. Schematic and hookup of T874P with Q674C. Used in heat pump applications. 113 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS RESET FAN SWITCH 1 H1 ANTICIPATOR X RESET LED (RED) G AUTO FALL H1 FAN RELAY ON 4 H2 2 FALL SETBACK CONTACT L2 1 R2 3 8 COOL CHANGEOVER VALVE 9 CO SYSTEM SWITCH C1 ANTICIPATOR RISE RISE O OFF 10 C1 L1 (HOT) R1 6 COMPRESSOR CONTACTOR AUTO Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SETBACK CONTACT ON Q674C1124. 3 H2 ON T874G. M7027 Fig. 79. Schematic and hookup of T874G,H with Q674C. Used in standard applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE W1 FALL HEAT RELAY 1 1 H1 Y1 H1 ANTICIPATOR 4 FAN SWITCH AUTO G ON FAN RELAY RC H2 ANTICIPATOR H2 CONTACTOR COMPRESSOR 1 2 6 FALL SYSTEM SWITCH 8 HEAT RELAY 2 W2 OFF L1 (HOT) L2 1 RH HEAT RISE AUTO C1 9 C SERVICE LED (RED) COOL Z C1 ANTICIPATOR 10 COMPRESSOR FAULT C2 ANTICIPATOR 11 C2 RISE COMPRESSOR CONTACTOR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M5997 Fig. 80. Schematic and hookup of T874D with Q674E. Used in standard applications. 60-2485—8 114 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CHANGEOVER RELAY FALL H1 1 W1 B 4 FAN SWITCH FAN RELAY AUTO FALL G H2 ANTICIPATOR 6 ON H2 R 8 SYSTEM SWITCH RISE C1 OFF 9 COMPRESSOR CONTACTOR W2 Y1 AUTO C1 ANTICIPATOR 10 1 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 L2 (HOT) M5981 Fig. 81. Schematic and hookup of T874C with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 RH FALL H1 HEAT RELAY 1 1 H1 ANTICIPATOR W1 FAN SWITCH AUTO 2 HEAT RELAY 2 ON 4 W2 H2 ANTICIPATOR O 6 FALL 3 H2 8 RISE SYSTEM SWITCH FAN RELAY G OFF C1 B 9 C1 ANTICIPATOR COMPRESSOR CONTACTOR 2 HEAT 10 AUTO Y2 COMPRESSOR CONTACTOR 1 COOL C2 ANTICIPATOR 11 1 C2 RISE Y1 L2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RC, RH FOR SINGLE TRANSFORMER. 3 O AND B TERMINALS ON SELECTED MODELS. 1 RC L1 (HOT) M934 Fig. 82. Schematic and hookup of T874A,C,D with Q674E. Used in standard applications. 115 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) 1 L2 H1 ANTICIPATOR HEAT RELAY 1 W1 1 FALL COMPRESSOR CONTACTOR 1 H1 Y1 FAN SWITCH AUTO 4 FAN RELAY G H2 ANTICIPATOR ON RC FALL HEAT RELAY 2 6 H2 W2 8 RISE RH C1 OFF 9 CHECK LED (RED) HEAT X1 COMPRESSOR CONTACTOR 2 AUTO C1 ANTICIPATOR 10 Y2 COOL C2 ANTICIPATOR 11 L2 RISE 1 C2 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 L1 (HOT) M5982 Fig. 83. Schematic and hookup of T874G with Q674C. Used in standard applications. THERMOSTAT SUBBASE 1 SYSTEM COMPONENTS R H1 ANTICIPATOR COOL CHANGEOVER VALVE 2 OUTDOOR FAN RELAY FAN SWITCH FALL H1 DEFROST SWITCH AUTO DEFROST RELAY 4 ON M HIGH PRESSURE SWITCH COMPRESSOR CONTACTOR H2 ANTICIPATOR 6 F DEFROST RELAY FALL H2 FAN RELAY 8 SYSTEM SWITCH C1 ANTICIPATOR 9 CO RISE V OFF DEFROST RELAY HEAT AUX. HT. RELAY Y AUTO 10 COOL L2 RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 (HOT) Fig. 84. Schematic and hookup of T874G with Q674E. Used in heat pump applications. 60-2485—8 116 1 M4666 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 H1 ANTICIPATOR H1 1 W1 COMPRESSOR CONTACTOR 1 FALL Y1 FAN SWITCH 4 FAN RELAY AUTO G 6 ON FALL L1 (HOT) R H2 ANTICIPATOR L2 H2 8 1 SYSTEM SWITCH RISE C1 OFF 9 HEAT HEAT RELAY 2 AUTO C1 ANTICIPATOR W2 COOL 10 COMPRESSOR CONTACTOR 2 C2 ANTICIPATOR RISE 11 1 C2 Y2 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5983 Fig. 85. Schematic and hookup of T874A-D with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 H1 ANTICIPATOR R 1 2 FALL FAN SWITCH AUTO COOL CHANGEOVER VALVE D. F. O. DEFROST SWITCH DEFROST RELAY H1 3 H2 ON M 5 FALL HIGH PRESSURE SWITCH 6 H2 ANTICIPATOR COMPRESSOR CONTACTOR F 8 C1 ANTICIPATOR RISE 9 SYSTEM SWITCH FAN RELAY V OFF DEFROST RELAY CONTACT HEAT Y AUTO DEFROST RELAY CONTACT CO 10 AUX. HT. RELAY 1 COOL C1 L2 RISE VR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M4667 L1 (HOT) Fig. 86. Schematic and hookup of T874G with Q674E. Used in heat pump applications. 117 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS W1 1 HEAT RELAY 1 FALL H1 Y1 FAN SWITCH H1 ANTICIPATOR COMPRESSOR CONTACTOR 1 AUTO G ON 4 FAN RELAY L1 (HOT) L2 RC H2 ANTICIPATOR 1 FALL W2 6 H2 HEAT RELAY 2 SYSTEM SWITCH B 2 RISE OFF 8 RH HEAT C1 L2 1 L1 (HOT) X AUTO SYSTEM FAULT CONTACT 9 COOL C1 ANTICIPATOR RISE C 10 C2 ANTICIPATOR 11 C2 COMPRESSOR CONTACTOR 2 LOCKOUT LED (RED) Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M4668 Fig. 87. Schematic and hookup of T874D with Q674E. Used in standard applications. THERMOSTAT SUBBASE 1 H1 ANTICIPATOR FALL H1 SYSTEM COMPONENTS W1 FAN SWITCH HEAT RELAY 1 G AUTO 4 1 FAN RELAY ON L1 (HOT) L2 RC FALL H2 ANTICIPATOR W2 6 H2 HEAT RELAY 2 SYSTEM SWITCH RISE 8 C1 OFF RH HEAT L2 1 L1 (HOT) AUTO 9 COOL C1 ANTICIPATOR RISE X HIGH LED (RED) 10 C2 ANTICIPATOR C2 1 11 Y2 COMPRESSOR CONTACTOR 2 LOW LED (GREEN) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 Y1 Fig. 88. Schematic and hookup of T874B,D with Q674E. Used in standard applications. 60-2485—8 118 M4669 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS B H1 ANTICIPATOR HEAT RELAY 1 1 HEAT CHANGEOVER VALVE W1 FAN SWITCH FALL H1 AUTO COMPRESSOR CONTACTOR 1 ON 4 Y1 6 G FAN RELAY H2 FALL 8 C1 HEAT RELAY 2 SYSTEM SWITCH 9 AUTO 10 COOL L2 X SERVICE LED (RED) 11 Y2 C2 ANTICIPATOR COOL CHANGEOVER VALVE O 1 1 COMPRESSOR CONTACTOR 2 A C1 ANTICIPATOR RISE 1 L1 (HOT) RH FILTER LED (YEL) HEAT RISE L2 W2 OFF C2 L1 (HOT) RC H2 ANTICIPATOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7023 Fig. 89. Schematic and hookup of T874D with Q674E. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS FILTER LED (YEL) X2 H1 ANTICIPATOR SERVICE LED (RED) 1 A2 HEAT RELAY 1 H1 W1 FALL 4 FILTER LED (YEL) NO FAN SWITCH X1 SERVICE LED (RED) 5 A1 6 W2 T RELAY H2 ANTICIPATOR HEAT RELAY 2 T FALL H2 7 L1 (HOT) RC 8 HEAT CHANGEOVER VALVE SYSTEM SWITCH OFF C1 L2 1 B RISE L1 (HOT) AUTO 9 RH COOL CHANGEOVER VALVE 10 C1 ANTICIPATOR L2 1 COMPRESSOR CONTACTOR 2 O 11 Y2 C2 RISE C2 ANTICIPATOR 12 COMPRESSOR CONTACTOR 1 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7022 Fig. 90. Schematic and hookup of T874D with Q674G. Used in standard applications. 119 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES H1 ANTICIPATOR FALL SYSTEM COMPONENTS SUBBASE THERMOSTAT 1 L1 (HOT) L2 RH NO FAN SWITCH HEAT RELAY 1 W1 H1 1 HEAT RELAY 2 4 W2 H2 6 FALL H2 ANTICIPATOR SYSTEM SWITCH B 8 HEAT DAMPER OFF RISE O AUTO C1 9 COOL DAMPER 2 Y2 10 COMPRESSOR CONTACTOR 2 C1 ANTICIPATOR Y1 C2 ANTICIPATOR 11 C2 RISE RC 1 2 COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L2 L1 (HOT) 1 M3201B JUMPER RH, RC FOR SINGLE TRANSFORMER. Fig. 91. Schematic and hookup of T874A-F,Q with Q674G. Used in standard applications. THERMOSTAT H1 ANTICIPATOR SUBBASE SYSTEM COMPONENTS 1 W1 NO FAN SWITCH 3 CHANGEOVER RELAY FALL H1 B 4 W2 H2 ANTICIPATOR FAN RELAY 6 G FALL H2 8 SYSTEM SWITCH OFF 9 AUTO Y1 COMPRESSOR CONTACTOR C1 R 1 C1 ANTICIPATOR RISE 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 92. Schematic and hookup of T874C with Q674G. Used in heat pump applications. 60-2485—8 120 1 L2 L1 (HOT) M6008A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 SUBBASE SYSTEM COMPONENTS FALL HEAT FAN RELAY 1 W1 NO FAN SWITCH H1 ANTICIPATOR HEAT RELAY 4 6 H2 ANTICIPATOR FALL H2 W2 SYSTEM SWITCH 8 RISE C1 L2 1 OFF HEAT COMPRESSOR CONTACTOR 1 AUTO Y1 9 C1 ANTICIPATOR 10 L1 (HOT) RH COOL L1 (HOT) RC L2 C2 ANTICIPATOR 1 RISE 11 C2 1 Y2 COMPRESSOR CONTACTOR 2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M4664 Fig. 93. Schematic and hookup of T874D with Q674K. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS B H1 ANTICIPATOR 1 NO FAN SWITCH HEAT CHANGEOVER VALVE W1 FALL H1 HEAT RELAY 2 4 HEAT RELAY 1 W2 6 L2 1 RH L1 (HOT) H2 ANTICIPATOR H2 FALL L1 (HOT) RC FILTER LED (YELLOW) 8 C1 L2 1 X SYSTEM SWITCH RISE 9 OFF AUTO SERVICE LED (RED) A COMPRESSOR CONTACTOR 1 Y1 COMPRESSOR CONTACTOR 2 10 C1 ANTICIPATOR Y2 11 C2 COOL CHANGEOVER VALVE O C2 ANTICIPATOR RISE "T" RELAY T 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7013 Fig. 94. Schematic and hookup of T874D with Q674G. Used in standard applications. 121 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTATS SUBBASE 1 SYSTEM COMPONENTS L1 (HOT) R NO FAN SWITCH FALL H1 ANTICIPATOR L2 1 2 H1 3 OIL RELAY SYSTEM SWITCH 4 W2 OFF OIL LED (RED) FALL WOOD 5 X WOOD/OIL H2 WOOD LED (GREEN) OIL H2 ANTICIPATOR WOOD RELAY W1 6 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5984 Fig. 95. Schematic and hookup of T874F with Q674K. Used in wood/oil applications. THERMOSTAT 1 W1 FAN SWITCH H1 SYSTEM COMPONENTS SUBBASE NO. 1 HEAT RELAY FALL W2 AUTO HEAT DAMPER NO. 2 HEAT RELAY ON B 4 6 FALL H2 ANTICIPATOR H2 L2 SYSTEM SWITCH RH L1 (HOT) 8 C1 1 OFF RC RISE AUTO 9 O FAN RELAY 10 COOL DAMPER G C1 ANTICIPATOR 11 Y2 NO. 1 COMPRESSOR CONTACTOR Y1 ON LED (YELLOW) X SERVICE LED (RED) A 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. C Fig. 96. Schematic and hookup of T874C with Q674C. Used in standard applications. 60-2485—8 122 L2 L1 (HOT) M104A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS 1 H2 COMPRESSOR CONTACTOR 2 H1 ANTICIPATOR FALL Y 3 G FAN SWITCH 3 4 CLOSED-DAY OPEN-NITE AUTO ON 5 RISE FAN RELAY C L2 L1 (HOT) R OVERRIDE LED (RED) 6 CO SERVICE LED (RED) 1 B H1 8 SYSTEM SWITCH L C1 B RELAY OVERRIDE RISE X AUTO 9 S OFF COMPRESSURE FAILURE JUMPER 2 P 10 W C1 ANTICIPATOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED. 3 H2 MAKE OFFEST 8˚ F BELOW H1 MAKE. COOL CHANGEOVER VALVE M100A Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS SERVICE LED (RED) H1 ANTICIPATOR 1 HEAT RELAY 1 FALL CHANGEOVER RELAY ON 4 B SYSTEM SWITCH 8 C1 L2 L1 1 (HOT) RH 6 H2 ANTICIPATOR H2 HEAT RELAY 2 W2 AUTO H1 SYSTEM MONITOR W1 FAN SWITCH FALL A L1 (HOT) RC OFF O CHANGEOVER RELAY L2 1 HEAT RISE 9 G AUTO FAN RELAY 10 COOL Y2 C1 ANTICIPATOR RISE 11 C2 Y1 COMPRESSOR CONTACTOR 2 COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 T874A IS SINGLE-STAGE (NO W2 OR Y2). M5106A Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications. 123 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR SUBBASE 1 W1 3 OFF H1 HEAT RELAY 1 SYSTEM SWITCH 2 FALL SYSTEM COMPONENTS HEAT RELAY 2 4 W2 AUTO W3 5 6 Y2 H2 ANTICIPATOR 4 FALL H2 7 SERVICE LED (RED) FAN SWITCH A AUTO 8 C1 9 RISE G L2 ON C1 ANTICIPATOR 3 FAN RELAY R 2 1 10 L1 (HOT) MOMENTARY CIRCUIT O COMPRESSOR RELAY Y1 5 THERMISTER 1 11 T 12 T EXTERNAL TEMP. READOUT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 4 H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 5 THERMISTOR INTERNAL TO THERMOSTAT. 3 H1 AND C1 ARE DPST SWITCHES. Fig. 99. Schematic and hookup of T874C with Q674C. Used in standard applications. 60-2485—8 124 M531 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE H1 ANTICIPATOR 1 W1 3 OFF FALL HEAT RELAY 2 4 W2 AUTO HEAT RELAY 3 W3 5 FALL H3 Y2 6 4 H2 ANTICIPATOR FALL H2 HEAT RELAY 1 SYSTEM SWITCH 2 H1 SYSTEM COMPONENTS FAN SWITCH C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 SERVICE LED (RED) A AUTO 7 G 3 L2 ON 8 FAN RELAY R C1 2 1 9 MOMENTARY CIRCUIT RISE O C2 L1 (HOT) COMPRESSOR RELAY 10 RISE Y1 C2 ANTICIPATOR 5 THERMISTER 11 T 12 T EXTERNAL TEMP. READOUT 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 4 H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 5 THERMISTOR INTERNAL TO THERMOSTAT. 3 H1 AND C1 ARE DPST SWITCHES. M532 Fig. 100. Schematic and hookup of T874W with Q674C. Used in standard applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE COOL CHANGEOVER VALVE 2 H1/C1 ANTICIPATOR H1 C1 O AUTO G ON FAN RELAY FALL L1 (HOT) L2 R FAN SWITCH 3 1 4 W 5 H2 FALL 6 H2 ANTICIPATOR SYSTEM SWITCH X AUX. HT. RELAY EM. HT. LED (RED) EM. HT. HEAT B OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR COOL Y M3718A Fig. 101. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 125 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COMPRESSOR CONTACTOR 1 H1/C1 ANTICIPATOR 2 H1 F AUTO FAN RELAY ON C1 HIGH PRESSURE INTERNAL THERMOSTAT SWITCH M FAN SWITCH FALL OVERLOAD SWITCH V 3 4 FALL SUPPL. ELEC. HT. RELAY EM. HT. RELAY CONTACT TIME DELAY FAN RELAY Y 5 H2 OUTDOOR THERMOSTAT 6 2 H2 ANTICIPATOR EM. HT. RELAY 7 E SYSTEM SWITCH EM. HT. LED (RED) EM. HT. 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. HEAT X OFF VR 2 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. COOL COOL CHANGEOVER VALVE R L1 L2 (HOT) 1 L1 L2 1 (HOT) Fig. 102. Schematic and hookup of T874J,R with Q674L. Used in heat pump applications. 60-2485—8 126 M4726 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE 1 L1 (HOT) O 1 H1 ANTICIPATOR L2 FAN SWITCH AUTO G ON 2 FAN RELAY R OUTDOOR THERMOSTAT FALL H1 4 W2 HEAT RELAY 1 FALL H2 6 HEAT RELAY HEAT RELAY 2 CONTACT 1 H2 ANTICIPATOR SYSTEM SWITCH E 8 HEAT RELAY CONTACT 2 2 HEAT RELAY 3 SUPL. HT. 9 L HEAT RISE CO SUPL. HT. LED (RED) OFF C1 ANTICIPATOR 10 C COMPRESSOR CONTACTOR 1 COOL Y C1 RISE 1 COMPRESSOR FAULT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 N.O. SWITCH – INSTALLER ADDED, TO LIGHT SUPL. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL. M4665 Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS E 2 H1 H1/C1 ANTICIPATOR C1 EM. HT. RELAY EM. HT. LED (RED) FAN SWITCH X 3 FALL B AUTO "B" RELAY ON R 4 AUX. HT. RELAY W2 5 6 FALL H2 H L1 (HOT) SYSTEM SWITCH L2 EM. HT. 1 2 COMPRESSOR CONTACTOR 2 H2 ANTICIPATOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. HEAT OPTIONAL FIELD WIRE JUMPER TO CYCLE AUXILIARY HEAT RELAY H1 INSTEAD OF H2 (FASTER RESPONSE). COOL 1 Y Y R COM OFF G G R8233B ELEC. HT. RELAY W O O EH M4728 Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 127 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FAN SWITCH H1 ANTICIPATOR FAN RELAY AUTO G ON 2 HEAT RELAY 2 W2 H1 FALL K L 4 SYSTEM SWITCH 6 FALL EM. HT. LED (RED) EM. HT. H2 ANTICIPATOR EM. HT. RELAY SYSTEM MONITOR SWITCH IHRI C HEAT H2 R 8 OFF RHI COMPRESSOR CONTRACTOR COOL C1 ANTICIPATOR Y RISE 10 W1 C1 1 HEAT RELAY 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 M8384 L1 L2 (HOT) Fig. 105. Schematic and hookup of T874C with Q674L. Used in heat pump applications. SYSTEM COMPONENTS SUBBASE THERMOSTAT COOL CHANGEOVER VALVE FALL 2 H1 C1 O FAN SWITCH H1/C1 ANTICIPATOR FAN RELAY AUTO G 3 ON L1 (HOT) L2 1 R 4 5 6 SYSTEM SWITCH HEAT H2 FALL H2 ANTICIPATOR AUX. HT. RELAY EM. HT. OFF W2 EM. HT. LED (RED) X COMPRESSOR CONTACTOR COOL 1 Y POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. EM. HT. RELAY E Fig. 106. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 128 M4724 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE 2 O FAN SWITCH FAN RELAY AUTO H1 ANTICIPATOR H1 G FALL 3 ON OUTDOOR THERMSTAT SUPPL. HT. RELAY 4 H2 ANTICIPATOR Y1 5 EM. HT. RELAY CONTACT H2 COMPRESSOR CONTACTOR 2 FALL E 8 SYSTEM SWITCH EM. HT. RELAY COMP. FAILURE L C1 ANTICIPATOR C1 RISE 10 C2 ANTICIPATOR EM. HT. LED (RED) EM. HT. C HEAT L1 (HOT) OFF R 11 COOL C2 L2 RISE 1 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 M4727 Fig. 107. Schematic and hookup of T874D with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 R H1/C1 ANTICIPATOR H1 2 C1 FAN SWITCH FAN RELAY AUTO FALL 3 G ON 4 AUX. HT. RELAY FALL 5 W 6 AUX. HT. LED (YELLOW) H2 H2 ANTICIPATOR SYSTEM SWITCH B EM. HT. LED (RED) EM. HT. 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. HEAT X OFF O COOL CHANGEOVER VALVE COOL COMPRESSOR CONTACTOR Y M4725 Fig. 108. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 129 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS AUX. HT. RELAY 1 W AUX. HT. LED (GREEN) 2 B H1 C1 FALL H1/ C1 ANTICIPATOR 3 FAN SWITCH AUTO EM. HT. LED (RED) F G 4 ON COMPRESSOR FAILURE FAN RELAY L1 (HOT) L2 1 R 5 RESET HEATER FALL X2 H2 6 T OUTDOOR THERMOSTAT SYSTEM SWITCH COOL CHANGEOVER VALVE EM. HT. HEAT 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. OUTDOOR THERMISTOR O OFF COMPRESSOR CONTACTOR COOL Y M5071 Fig. 109. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 130 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS RESET 1 L1 (HOT) L2 1 V 2 2 H1 ANTICIPATOR VR INTERNAL THERMOSTAT COMPRESSOR CONTACTOR M 3 FAN SWITCH FAN RELAY H1 OVERLOAD SWITCH HI PRESSURE SWITCH AUTO FALL 4 F ON SERVICE SERVICE LED (RED) L OUTDOOR THERMOSTAT SUPL. ELEC. HT. RELAY 5 S H2 6 Y H2 ANTICIPATOR 7 ELEC. HT. RELAY SYSTEM SWITCH E EM. HT. LED (YELLOW) EM. HT. 8 X HEAT C1 C1 ANTICIPATOR TIME DELAY FAN RELAY EM. HT. RELAY CONTACT 3 FALL C815A OUTDOOR THERMISTOR OFF A RISE COOL COOL CHANGEOVER VALVE 10 R 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 3 REMOVE FACTORY-INSTALLED S-Y JUMPER TO DISABLE SERVICE LIGHT. M2854 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. Fig. 110. Schematic and hookup of T87C,R with Q674L. Used in heat pump applications. 131 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS V 1 RESET HEATER 1 L1 (HOT) 2 L2 VR 2 H1/ C1 ANTICIPATOR COMPRESSOR CONTACTOR 3 M FAN SWITCH 4 INTERNAL THERMOSTAT OVERLOAD SWITCH AUTO HIGH PRESSURE SWITCH F ON H1 FAN RELAY C1 SERVICE L SERVICE LED (RED) FALL OUTDOOR THERMOSTAT 5 6 Y EM. HT. RELAY SYSTEM SWITCH H2 7 SUPPL. ELEC. HT. RELAY E EM. HT. X OFF A COOL C815A OUTDOOR THERMISTOR COOL CHANGEOVER VALVE H2 ANTICIPATOR 1 EM. HT. RELAY EM. HT. LED (YELLOW) HEAT FALL EM. HT. RELAY R POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. Fig. 111. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 132 M2851 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE COOL CHANGEOVER VALVE FALL O 2 H1 FAN SWITCH C1 H1/C1 ANTICIPATOR AUTO FAN RELAY G L1 (HOT) ON R 3 4 H2 ANTICIPATOR 5 SYSTEM SWITCH 1 L1 EM. HT. 6 HEAT OFF H2 FALL COOL EM. HT. LED (RED) X AUX. HT. LED (GREEN) AUX. HT. RELAY W2 1 L2 COMPRESSOR FAILURE POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR Y EM. HT. RELAY E M8383 Fig. 112. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 133 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 R HEAT CONTRACTOR 3 EM. HT. RELAY H1/C1 ANTICIPATOR EM. HT. RELAY 1 W3 HEAT CONTRACTOR 2 OUTDOOR THERMOSTAT 2 DEFROST RELAY 3 H1 W2 HEAT CONTRACTOR 1 HIGH LIMIT SWITCH B DEFROST RELAY REVERSING VALVE C1 FALL FAN SWITCH AUTO 4 ON H2 FALL CHECK LED (GREEN) L 5 OPTIONAL COMP. FAILURE DEVICE X2 H2 ANTICIPATOR 6 SYSTEM SWITCH X1 EM. HT. LED (RED) EM. HT. RELAY E EM. HT. FAN RELAY 7 HEAT G OFF COOL COMPRESSOR CONTACTOR HIGH PRESSURE SWITCH Y 1 LOW AMBIENT CUTOFF POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE O M4720 Fig. 113. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 134 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS 1 RESET HEATER M2 OUTDOOR THERMOSTAT H1 ANTICIPATOR 2 HIGH SPEED COMPRESSOR CONTACTOR M 3 FAN SWITCH FAN RELAY AUTO LOW SPEED COMPRESSOR CONTACTOR F H1 ON FALL L1 (HOT) L2 1 V 4 5 R 2 H2 L FALL COOL CHANGEOVER VALVE SERVICE 6 H2 ANTICIPATOR X EM. HT. LED (YELLOW) 7 EM. HT. RELAY E OUTDOOR THERMOSTAT 8 SYSTEM SWITCH RISE C1 C1 ANTICIPATOR EM. HT. SUPPL. ELEC. HT. RELAY VR SERVICE LED (RED) HEAT 10 OFF EM. HT. RELAY COOL RISE C2 SUPPL. ELEC. HT. RELAY Y C2 ANTICIPATOR C815A OUTDOOR THERMISTOR A 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. M2853 Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications. 135 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS (HOT) L1 L2 1 H1/C1 ANTICIPATOR R 2 FALL ODT 1 H1 RTD 1 C1 EHR 1 RTD 2 W3 3 4 FAN SWITCH ODT 2 AUTO EHR 2 ON H2 ANTICIPATOR W2 5 H2 RTD 3 RTD 1 AUX. HT. LED (GREEN) 6 2 FALL X EM. HT. LED (RED) SYSTEM SWITCH SYSTEM MONITOR RD L FAN RELAY G EM. HT. O HEAT OFF COOL CHANGEOVER VALVE E COOL EM. HT. RELAY CHP LACO Y B 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 AUXILIARY HEAT LED AVAILABLE ON SOME MODELS. COMPRESSOR CONTACTOR M5072A Fig. 115. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 136 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1/C1 ANTICIPATOR H1 C1 3 FALL E FAN SWITCH EM. HT. RELAY AUTO X EM. HT. LED (RED) ON B 4 R AUX. HT. RELAY 5 W2 H2 ANTICIPATOR 6 2 SYSTEM SWITCH COMPRESSOR CONTACTOR H L1 (HOT) L2 EM. HT. H2 FALL A HEAT COMP. FAULT LED (YELLOW) OFF COOL 1 2 1 Y Y G G R COM POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. OPTIONAL FIELD WIRE JUMPER TO CYCLE AUXILIARY HEAT RELAY WITH H1 INSTEAD OF H2 (FASTER RESPONSE). R8233B ELEC. HT. RELAY W O O EH M2857 Fig. 116. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 137 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT L1 (HOT) L2 1 R DEFROST RELAY ENTHALPY CONTROL RELAY 2 B FALL H1 HEAT RELAY CONTACT 1 H1 ANTICIPATOR MOTOR 3 G 3 FAN SWITCH ECONOMIZER RELAY DEFROST SWITCH OUTDOOR FAN RELAY 1 AUTO 4 ON H2 ANTICIPATOR ENTHALPY CONTROL 5 FALL DEFROST SWITCH RELAY TM1 2 TM2 LOW AMBIENT THERMOSTAT 1 ENTHALPY CONTROL RELAY 2 H2 OUTDOOR FAN RELAY 3 OUTDOOR FAN RELAY 2 6 1ST STAGE LOW PRESSURE LIMIT 8 Y1 C1 ENTHALPY CONTROL RELAY 1 RISE 1ST STAGE SHORT CYCLE CONTROL MOTOR 1 2ND STAGE SHORT CYCLE CONTROL MOTOR 2 TIME DELAY HEATER TIME DELAY Y2 C1 ANTICIPATOR 2ND STAGE LOW PRESSURE LIMIT 10 DEFROST RELAY SYSTEM SWITCH C2 ANTICIPATOR W EM. HT. 11 LED (GREEN) HEAT OUTDOOR THERMOSTAT HEAT RELAY 1 X C2 RISE OFF SERVICE COOL SERVICE LED (RED) L DEFROST RELAY COOL CHANGEOVER VALVE O 1 2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES). Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications. 60-2485—8 138 M7755 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT 1 L1 (HOT) L2 1 R H1 DEFROST RELAY ECONOMIZER RELAY FALL 2 B H2 HEAT RELAY CONTACT 1 FALL G H1 ANTICIPATOR H2 ANTICIPATOR 3 4 H3 ANTICIPATOR ECONOMIZER RELAY DEFROST SWITCH FAN SWITCH MOTOR 3 AUTO OUTDOOR FAN RELAY 1 ON DEFROST RELAY ENTHALPY CONTROL DEFROST SWITCH RELAY 2 5 TM1 TM2 OUTDOOR THERMOSTAT 1 FALL H3 ECONOMIZER RELAY 2 6 1ST STAGE LOW PRESSURE LIMIT 8 C1 Y1 RISE ECONOMISER RELAY 1 9 SYSTEM SWITCH C1 ANTICIPATOR C2 ANTICIPATOR 10 OUTDOOR FAN RELAY 3 OUTDOOR FAN RELAY 2 1ST STAGE SHORT CYCLE CONTROL MOTOR 1 2ND STAGE SHORT CYCLE CONTROL MOTOR 2 TIME DELAY HEATER TIME DELAY RELAY EM. HT. Y2 HEAT DEFROST RELAY OFF 2ND STAGE LOW PRESSURE LIMIT COOL DEFROST RELAY CONTACT C2 RISE AUXILIARY HEAT RELAY W DEFROST RELAY CONTACT AUX. HEAT LED (GREEN) 11 COOL CHANGEOVER VALVE O RESET HEATER 12 X 1 2 EMERGENCY HEAT RELAY EM. HEAT LED (RED) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. E C815 OUTDOOR THERMISTOR OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES). A M7756 Fig. 118. Schematic and hookup of T874W with Q674L. Used in heat pump applications. 139 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 L1 (HOT) L2 C815A OUTDOOR THERMISTOR RESET HEATER 1 T H2 ANTICIPATOR W2 2 FAN SWITCH AUX. HT. RELAY AUTO G ON 3 FAN RELAY R X 4 H1 C1 FALL SERVICE LED (YELLOW) SYSTEM SWITCH 5 SERVICE Z EM. HT. C1 ANTICIPATOR EM. HT. LED (RED) HEAT 6 OFF K COOL FALL 1 H2 11 Y 12 W1 EM. HT. RELAY COMPRESSOR CONTACTOR H1 ANTICIPATOR HEAT CHANGEOVER RELAY POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5955 Fig. 119. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SYSTEM COMPONENTS SUBBASE THERMOSTAT L1 (HOT) 2 FALL H1 C1 H1/C1 ANTICIPATOR FAN SWITCH 1 FAN RELAY AUTO 3 L2 G ON R 4 AUX. HT. RELAY W 5 FALL H H2 6 H2 ANTICIPATOR B SYSTEM SWITCH "H" RELAY EM. HT. LED (RED) X EM. HT. RELAY EM. HT. T HEAT C815A1039 THERMISTOR OFF O COOL CHANGEOVER VALVE (COOL) 11 Y RESET HEATER COMPRESSOR CONTACTOR 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 120. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 140 M3173B T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT 2 H1 ANTICIPATOR SYSTEM COMPONENTS L1 (HOT) L2 1 R FAN SWITCH COMPRESSOR FAILURE 3 ODT1 AUTO RTD2 EHR1 H1 ON FALL 4 ODT2 EM. HT. LED (RED) 5 H2 ANTICIPATOR L RTD1 EHR2 RTD3 X 6 AUX. HT. LED (GRN) H2 FALL RTD1 W2 RD SYSTEM SWITCH 8 C1 ANTICIPATOR COOL CHANGEOVER VALVE EM. HT. HEAT 10 FAN RELAY G EM. HT. RELAY O OFF E COOL LACO C1 COMPRESSOR CONTACTOR CHP Y RISE HEAT CHANGEOVER VALVE B 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7012 Fig. 121. Schematic and hookup of T874C with Q674L. Used in heat pump applications. 141 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT FAN SWITCH SYSTEM COMPONENTS FAN RELAY G AUTO 2 FALL L2 ON R H1 C1 H1/C1 ANTICIPATOR 3 1 L1 (HOT) W2 AUX. HT. RELAY K EM. HT. RELAY 4 L CO SYSTEM SWITCH 5 FALL EM. HT. HEAT H2 H2 ANTICIPATOR 6 EM. HT. LED (YELLOW) OFF C SERVICE LED (RED) COMPRESSOR CONTACTOR COOL Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. W1 CHANGEOVER VALVE Z SERVICE Fig. 122. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 142 M8379 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) ODT 1 1 2 H1 C1 EHR 1 H1/C1 ANTICIAPTOR RTD 2 RTD 1 FALL 3 4 ODT 2 FAN SWITCH EHR 2 AUTO RTD 3 ON R 5 L H2 FALL EM. HT. LED (RED) H2 ANTICIPATOR COMPRESSOR MONITOR X 6 AUX. HT. LED (GREEN) RTD 1 W2 8 SYSTEM SWITCH RD EM. HT. 10 FAN RELAY G 2 COOL CHANGEOVER VALVE HEAT OFF 1 2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. O EM. HT. RELAY COOL E CHP LACO CONNECT CHANGEOVER RELAY TO B FOR HEAT CHANGEOVER, TO O FOR COOL CHANGEOVER. Y B COMPRESSOR CONTACTOR 2 HEAT CHANGEOVER VALVE M1030A Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 143 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 L2 (HOT) 1 FALL R FAN SWITCH H1 2 AUTO 3 ON H1 ANTICIPATOR COMPRESSOR CONTACTOR Y G EM. HT. OR SUPL. HT. LED (RED) 5 OUTDOOR THERMOSTAT L H2 6 RISE 8 SYSTEM SWITCH 9 EM. HT. OR SUPL. HT. C1 ANTICIPATOR CO 2 HEAT RELAY CONTACT 2 HEAT RELAY 2 HEAT RELAY 3 E HEAT X OFF COOL "P" RELAY "X" RELAY P RISE CO HEAT RELAY CONTACT 1 C 10 C1 HEAT RELAY 1 W2 4 H2 ANTICIPATOR FALL FAN RELAY 2 11 O 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 ON MODELS INCLUDING EXTERNAL JUMPER, W2=W1 AND L=F. COOL CHANGEOVER VALVE Fig. 124. Schematic and hookup of T874J with Q674L. Used in heat pump applications. 60-2485—8 144 M8003 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 (HOT) R L2 L 2 H1/C1 ANTICIPATOR 3 EM. HT. LED (RED) 3 FAN SWITCH C1 FALL 4 2 ON X H2 ANTICIPATOR H2 FALL AUX. HT. RELAY W3 AUTO H1 1 AUX. HT. LED (GRN) 6 AUX. HT. RELAY W2 SYSTEM SWITCH EM. HT. FAN RELAY G HEAT COOL CHANGEOVER VALVE OFF O COOL E EM. HT. RELAY Y COMPRESSOR CONTACTOR B 1 "B" RELAY POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. 3 W3 TERMINAL AVAILABLE ON SOME MODELS ONLY. M3683A Fig. 125. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 145 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE 1 L1 (HOT) L2 1 O H1 ANTICIPATOR FAN SWITCH FAN RELAY AUTO G 2 ON R FALL H1 OUTDOOR THERMOSTAT 4 W2 FALL HEAT RELAY 1 6 H2 H2 ANTICIPATOR HEAT RELAY CONTACT 1 8 CO HEAT RELAY CONTACT 2 2 9 RISE HEAT RELAY 3 SUPL. HT. L 10 HEAT SUPL. HT. LED (RED) COOL RISE C1 E SYSTEM SWITCH C1 ANTICIPATOR HEAT RELAY 2 C Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL. COMPRESSOR CONTACTOR 1 M4722 Fig. 126. Schematic and hookup of T874G with Q674P. Used in heat pump applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 (HOT) R ODT1 2 L2 RTD1 1 H1 ANTICIPATOR FALL EHR1 FAN SWITCH H1 W3 3 AUTO ON W2 H2 ANTICIPATOR 5 H2 8 RTD3 AUX.HT. LED (GREEN) X EM. HT. COMPRESSOR LED (RED) FAILURE HEAT OFF L COOL G RISE C1 EHR2 SYSTEM SWITCH EM. HT. 6 RTD2 RTD1 4 FALL ODT2 RD FAN RELAY O COOL CHANGEOVER VALVE E 10 C1 ANTICIPATOR LACO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. EM. HT. RELAY COMPRESSOR CONTACTOR B Fig. 127. Schematic and hookup of T874C with Q674L. Used in heat pump applications. 60-2485—8 CHP Y 146 M5652A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS R H1/C1 ANTICIPATOR 2 FALL C1 L2 A 1 SERVICE LED (RED) FAN SWITCH H1 L1 (HOT) ODT1 RD EHR1 RTD1 W3 3 AUTO ON RTD1 4 ODT2 RTD2 EHR2 RTD3 W2 FALL H2 ANTICIPATOR 5 AUX. HT. LED (GREEN) SYSTEM SWITCH H2 X EM. HT. 6 EM. HT. LED SYSTEM (YELLOW) MONITOR HEAT OFF RD L COOL FAN RELAY G 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. O COOL CHANGEOVER VALVE EM. HT. RELAY E LACO COMPRESSOR CONTACTOR CHP Y B M5653A Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN RELAY 2 FAN AUTO SWITCH ON H1 ANTICIPATOR H1 FALL G L1 (HOT) 1 L2 R 3 4 W H2 ANTICIPATOR EM. HT. RELAY FALL 6 H2 SYSTEM SWITCH AUX. HT. RELAY X EM. HT. EM. HT. LED (RED) HEAT B OFF RISE COOL 8 CO COOL CHANGEOVER VALVE O 9 C1 ANTICIPATOR RISE Y 10 C1 1 COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M102A Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications. 147 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 O COOL CHANGEOVER VALVE FAN SWITCH H1 G C1 AUTO FAN RELAY FALL ON L1 (HOT) L2 1 R H1/C1 ANTICIPATOR 3 W1 4 5 AUX. HT. LED (YELLOW) SYSTEM SWITCH FALL 6 EM. HT. RELAY E COMPRESSOR FAILURE EM. HT. H2 2 CHECK LED (RED) HEAT X H2 ANTICIPATOR OFF C COOL 11 C815A OUTDOOR THERMISTOR SYSTEM LED (GREEN) RESET T 12 1 2 COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y FACTORY-INSTALLED JUMPER. Fig. 130. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 148 M1628A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 H1/C1 ANTICIPATOR 2 AUTO FAN SWITCH ON R 3 H1 W2 C1 HCR 1 RESET HEATER FALL L 4 SYSTEM SWITCH ODT SUPL. HT. LED (RED) SUPL. HT. FAN RELAY G 6 HEAT COOL CHANGEOVER VALVE 2 H2 ANTICIPATOR H2 C FALL O COOL E HCR 2 HCR 3 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FOR Q674L1454, COMPRESSOR CONTACTOR IS "OFF". HCR 1 HCR 2 M4723 Fig. 131. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 149 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS O 2 FAN SWITCH FALL H1 C1 COOL CHANGEOVER VALVE FAN RELAY AUTO H1/C1 ANTICIPATOR G ON L1 (HOT) R 1 3 L2 3R 4 W1 5 SYSTEM SWITCH AUX. HT. LED (YELLOW) EM. HT. 6 H2 H2 ANTICIPATOR FALL SEQ 1 2 SEQ 2 HEAT E OFF COOL EM. HT. LED (RED) EM. HT. RELAY 4R 4R X C SYSTEM LED (GREEN) 11 5R C815A OUTDOOR THERMISTOR 4R HPS T 12 RESET Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS. 4R COMPRESSOR CONTACTOR M1858 Fig. 132. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT 1 H1/C1 ANTICIPATOR FAN SWITCH FAN RELAY G L1 (HOT) AUTO 2 H1 SYSTEM COMPONENTS R L2 1 ON C1 K FALL W2 EM. HT. RELAY AUX. HT. RELAY 3 L 4 EM. HT. LED (YEL) SYSTEM SWITCH C 5 COMPRESSOR FAILURE EM. HT. 6 H2 ANTICIPATOR H2 FALL Z HEAT RESET LED (RED) OFF CO W1 RELAY W1 COOL COMPRESSOR CONTACTOR Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 133. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 150 M2018 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RTD 1 ODT 1 1 H1 EHR 1 RTD 2 C1 FALL ODT 2 2 EHR 2 H1/C1 ANTICIPATOR RDT 3 FAN SWITCH 3 FAN RELAY AUTO G ON 4 L1 (HOT) 1 L2 R H2 ANTICIPATOR W2 5 AUX. HT. LED (GREEN) RTD 1 EM. HT. RELAY E 6 FALL COMP. FAILURE H2 L SYSTEM SWITCH 8 RD EM. HT. LED (RED) CHANGEOVER VALVE (HEAT) EM. HT. B HEAT X OFF COOL LACO 10 COMPRESSOR CONTACTOR CHP Y CHANGEOVER VALVE (COOL) O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M106A Fig. 134. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 151 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS FAN SWITCH L1 (HOT) R AUTO H1/C1 ANTICIPATOR 2 L2 1 ON W2 HCR 1 3 H1 C1 L SUPL. HT. LED (RED) RESET HEATER FALL HCR 2 HCR 1 ODT C 4 SYSTEM SWITCH G FAN RELAY SUPL. HT. O 6 COOL CHANGEOVER VALVE HEAT H2 ANTICIPATOR OFF E COOL H2 HCR 3 HCR 2 FALL Y COMPRESSOR CONTACTOR 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2017 Fig. 135. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS G 1 FAN RELAY C1 ANTICIPATOR W H1 ANTICIPATOR FAN SWITCH AUX. HT. LED (GRN) U AUX. HEAT RELAY 1 2 AUTO 3 H1 ON EM. HT. LED (RED) B F C1 COMP. FAILURE 2 4 FALL L2 RESET H2 FALL 5 R 6 T SYSTEM SWITCH EM. HT. X2 O.D. STAT HEAT OFF FIELD REMOVABLE JUMPER C815A OUTDOOR THERMISTOR COOL CHANGEOVER VALVE O COOL 1 L1 (HOT) COMPRESSOR CONTACTOR Y 2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 136. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 152 M2012 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RTD 1 ODT 1 1 H1 EHR 1 RTD 2 C1 FALL ODT 2 2 EHR 2 H1/C1 ANTICIPATOR 3 RDT 3 W3 FAN SWITCH FAN RELAY AUTO G ON L1 (HOT) 1 L2 R 4 H2 ANTICIPATOR W2 5 AUX. HT. LED (GREEN) RTD 1 EM. HT. RELAY E 6 FALL H2 COMP. FAILURE EM. HT. LED (RED) SYSTEM SWITCH RD L CHECK LED (RED) EM. HT. CHANGEOVER VALVE (HEAT) B HEAT X OFF COMPRESSOR CONTACTOR COOL LACO CHP Y CHANGEOVER VALVE (COOL) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. O M105A Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 153 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 J R1 NO2 S1 RELAY 2 S1 NC H1 S FALL FAN SWITCH H1 ANTICIPATOR SOLIENOID RELAY AUTO ON FAN RELAY G L1 (HOT) L2 1 R 3 2 4 C 5 H2 H2 ANTICIPATOR FALL AUX. HT. RELAY H2 SYSTEM SWITCH HEAT RISE 8 C1 COMPRESSOR CONTACTOR R1 NC1 7 H1 OFF R2 NO1 COOL 9 REVERSING VALVE C1 ANTICIPATOR 10 O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD REMOVABLE JUMPER R1 RELAY M103A Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FAN RELAY AUTO H1 ANTICIPATOR G 2 ON FAN SWITCH R L1 (HOT) L2 1 FALL H1 B 4 H2 ANTICIPATOR 6 SYSTEM SWITCH W1 COMPRESSOR RELAY AUX. HT. H2 HEAT PUMP FALL 8 C1 RISE 2 STG. HEAT OFF C1 ANTICIPATOR HEAT PUMP LED (GREEN) COOL AUX. HT. RELAY W2 AUX. HT LED (RED) C COOL CHANGEOVER VALVE 10 O C2 ANTICIPATOR Y1 COMPRESSOR CONTACTOR 1 11 C2 RISE 1 Y2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 2 Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications. 60-2485—8 154 M4730 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 1 FALL H1 ANTICIPATOR T H1 2 C815A OD THERMISTOR W3 H2 H2 ANTICIPATOR FALL AUX. HT. RELAY 3 AUX. HT. LED (GREEN) FAN SWITCH AUTO H3 ANTICIPATOR 4 U G ON FAN RELAY H3 FALL EM. HT. LED (RED) 5 R E 6 RESET EM. HT. RELAY COMPRESSOR MONITOR L CHECK LED (RED) RISE X 8 C1 SYSTEM SWITCH B EM.HT. 2 9 HEAT C1 ANTICIPATOR HEAT CHANGEOVER RELAY COOL CHANGEOVER RELAY OFF 10 O COOL COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR RISE C2 11 Y1 12 Y2 COMPRESSOR CONTACTOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING. M156A Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications. 155 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT R FALL FAN SWITCH 1 H1 ANTICIPATOR H1 W1 FAN RELAY AUTO G ON 4 FALL HEAT RELAY 2 6 W2 H2 H2 ANTICIPATOR EM. HT. LED (RED) SYSTEM SWITCH OFF X2 EM. HT. RELAY RISE EM. HT. C1 E 8 HEAT COMPRESSOR CONTACTOR 2 9 AUTO C1 ANTICIPATOR Y2 COOL COMPRESSOR CONTACTOR 1 10 C2 ANTICIPATOR C2 RISE L1 (HOT) L2 1 HEAT RELAY 1 Y1 11 M8376 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 141. Schematic and hookup of T874C with Q674F. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) R FAN SWITCH FALL H1 1 H1 ANTICIPATOR L2 1 AUTO W1 ON HEAT RELAY 1 4 H2 ANTICIPATOR W2 6 HEAT RELAY 2 B FALL H2 X2 CHECK LED (RED) SYSTEM SWITCH OFF RISE X1 E EM. HT. RELAY EM. HT. C1 8 G HEAT FAN RELAY AUTO 9 Y2 COOL C1 ANTICIPATOR COMPRESSOR CONTACTOR 2 10 C2 ANTICIPATOR Y1 11 O C2 RISE COMPRESSOR CONTACTOR 1 M5985 1 POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 142. Schematic and hookup of T874C,D with Q674F. Used in standard applications. 60-2485—8 156 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE 1 FALL Y1 H1 ANTICIPATOR H1 COMPRESSOR CONTACTOR FAN SWITCH 2 FAN RELAY AUTO G 4 ON FALL R L1 (HOT) 6 L2 SYSTEM SWITCH H2 H2 ANTICIPATOR 1 OFF W1 AUTO 8 RISE AUX. HT. RELAY C CO C1 ANTICIPATOR AUX. HT. LED (RED) 9 O 1 10 C1 COOL CHANGEOVER VALVE POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M8378 RISE Fig. 143. Schematic and hookup of T874G with Q674B. Used in heat pump applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 L2 (HOT) 1 R FAN SWITCH FALL COMPRESSOR CONTACTOR Y H1 AUTO 2 G ON FAN RELAY 3 W2 HEAT RELAY 1 H1 ANTICIPATOR OUTDOOR THERMOSTAT 4 H2 ANTICIPATOR SUPP. HT. LED (RED) L 5 HEAT RELAY CONTACT 1 H2 FALL HEAT RELAY 2 C 6 E 8 RISE HEAT RELAY CONTACT 2 9 SYSTEM SWITCH X C1 ANTICIPATOR CO "P" RELAY SUPL. HT. 10 HEAT RELAY 3 "X" RELAY P ON RISE C1 CO COOL CHANGEOVER VALVE OFF 11 12 O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5956 Fig. 144. Schematic and hookup of T874J with Q674J. Used in heat pump applications. 157 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS (HOT) L1 L2 1 V FAN SWITCH H1 ANTICIPATOR DEFROST RELAY SUP. ELEC. HT. RELAY 1 Y AUTO 2 FALL H1 OUTDOOR THERMOSTAT ON EM. HT. RELAY 4 FAN RELAY SYSTEM SWITCH H2 ANTICIPATOR FALL TIME DELAY FAN RELAY F EM. HT. RELAY 6 OFF H2 E EM. HT. LED (RED) EM. HT. 8 HEAT FALL COOL CHANGEOVER VALVE AUTO 9 R CO COOL C1 ANTICIPATOR COMPRESSOR CONTACTOR 10 1 RISE C1 INTERNAL THERMOSTAT M POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. HIGH PRESSURE SWITCH OVERLOAD M8375 Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS W1 1 EHR EHR REVERSING RELAY H1 LPCO FALL Y1 H1 ANTICIPATOR RVR 3 DFR 2 4 H2 ANTICIPATOR H2 COMPRESSOR CONTACTOR 1 RVR FAN SWITCH FAN RELAY AUTO G ON 6 L1 (HOT) L2 1 R FALL ODT 3 HEAT RELAY 2 8 W2 C1 SYSTEM SWITCH RISE ODT 2 OFF HEAT RELAY 3 SUPL. HT. 9 C1 ANTICIPATOR E HEAT 10 X AUTO SUPL. HEAT LED (RED) COOL C2 ANTICIPATOR RISE C2 HEAT RELAY 1 EHT 11 SUPL. HT. RELAY C DFR 2 COMPRESSOR CONTACTOR 2 Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications. 60-2485—8 158 M7010 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS A 2 H1 H1 ANTICIPATOR MODE SIGNAL 1 3 FALL 3 FAN SWITCH 2 4 AUTO G FAN RELAY ON 5 L1 (HOT) L2 1 R H2 ANTICIPATOR 2 S SERVICE LED (RED) 6 W3 FALL H2 HEAT RELAY 2 HEAT RELAY 1 SYSTEM SWITCH W2 AUX. HT. LED (GRN) OFF X 8 COOL CO EM. HT. LED (YEL) AUTO COOL CHANGEOVER VALVE O 9 RISE L COMPRESSOR CONTACTOR HEAT EM. HT. Y EM. HT. RELAY C1 ANTICIPATOR RISE E 10 C1 T 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER. 3 MODE SIGNAL JUMPER FACTORY INSTALLED. M7024 Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS H1 ANTICIPATOR O 1 COOL CHANGEOVER VALVE DEFROST RELAY 2 BLOWER SPEED RELAY FAN SWITCH BLOWER RELAY AUTO G FALL H1 ON L1 (HOT) R L2 4 1 6 SYSTEM SWITCH FALL H2 ANTICIPATOR OFF H2 8 CO RISE 9 EM. HT. DEFROST AUX. HT. RELAY RELAY EM. HT. LED (RED) W2 EM. HT. RELAY HEAT E AUTO C LOCKOUT THERMOSTAT COOL C1 ANTICIPATOR C1 RISE COOL CONTRACTOR Y 10 M8382 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 159 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2R EMR4 FALL W1 1 H1 1R Y1 H1 ANTICIPATOR 4R2 2R2 5R 4 FALL G EMR4 H2 H2 ANTICIPATOR 6 3R W2 EMR2 THERMAL SWITCHES FOR HEATING ELEMENTS HTR 1 8 RISE FAN SWITCH C1 HTR 3 AUTO HTR 2 EMR3 ON 9 C1 ANTICIPATOR RISE 3 C2 10 2 EM. HT. LED C2 ANTICIPATOR X1 11 SYSTEM SWITCH 3R1 Z OFF 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. 3 FOR Q674F1048, DELETE C2 STAGE. OUTDOOR THERMOSTAT RC EM. HT. EMR1 EMR1 HEAT RH AUTO COOL EM. HT. RELAY E L1 (HOT) L2 1 L1 L2 (HOT) 1 M8380 Fig. 149. Schematic and hookup of T874C with Q674F. Used in heat pump applications. 60-2485—8 160 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE H1 ANTICIPATOR 1 R COMPRESSOR CONTACTOR FALL INTERNAL THERMOSTAT M 2 H1 OVERLOAD SWITCH FAN SWITCH AUTO 3 F HI PRESSURE SWITCH FAN RELAY ON OUTDOOR THERMOSTAT FALL 5 SUPL. ELEC. HT. RELAY Y H2 EM. HT. RELAY CONTACT H2 ANTICIPATOR TIME DELAY FAN RELAY 6 SYSTEM SWITCH RISE 8 TIME DELAY FAN RELAY E OFF EM. HEAT LED (RED) EM. HT. C1 X HEAT RISE CO 9 SYSTEM MONITOR COOL 1 L1 HOT L2 AUTO C1 ANTICIPATOR VR 2 10 L2 V 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM. 1 L1 HOT M2852A Fig. 150. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 161 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS EM. HT. RELAY CONTACT 1 L2 L1 (HOT) H1 ANTICIPATOR 1 R 1 W2 2 FAN SWITCH AUTO FALL H1 T6031 REFRIGERATON/ TEMPERATURE CONTROLLER EM. HT. LED (RED) ON EM. HT. E 4 2 6 SYSTEM SWITCH H2 ANTICIPATOR EM. HT. RELAY X H OFF FALL H2 Y EM. HT. HEAT R8233B Y COMPRESSOR CONTACTOR R COM AUTO G 8 G EM. HT. COOL CO W RISE 9 O SEQUENTIAL RELAY O FAN C1 ANTICIPATOR C DF RS 10 C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HT. (FASTER RESPONSE). RISE 1 L1 (HOT) L2 REVERSING SOLENOID Fig. 151. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485—8 162 FAN M4710 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 L1 L2 (HOT) HEAT RELAY W1 COMPRESSOR CONTRACTOR 1 1 FALL H1 Y1 FAN SWITCH H1 ANTICIPATOR FAN RELAY AUTO G ON 4 RC 3 FALL H2 ANTICIPATOR H2 HEAT RELAY 2 W2 6 SYSTEM SWITCH RISE RH EM. HT. RELAY OFF 8 E EM. HT. C1 HEAT 9 B AUTO 10 RISE C1 ANTICIPATOR 2 X2 COOL EM. HEAT LED (RED) 11 C2 X1 C2 ANTICIPATOR COMPRESSOR CONTRACTOR 2 O Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FACTORY SUPPLIED FIELD INSTALLED JUMPER TO E-X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION. 3 1 L1 L2 (HOT) OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M8377 Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS COOL CHANGEOVER VALVE 1 O H1 ANTICIPATOR FAN RELAY AUTO G 2 H1 ON L1 (HOT) L2 1 FAN SWITCH FALL 4 R 6 W2 SYSTEM SWITCH FALL OUTDOOR THERMOSTAT AUX. HT. RELAY H2 ANTICIPATOR OFF H2 8 C1 RISE AUX. HT. RELAY CONTACT EM. HT. RELAY HEAT 9 CO E EM. HT. RISE AUTO COOL EM. HT. LED (RED) X C1 ANTICIPATOR Y 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M8381 Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 163 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 R 1 H1 ANTICIPATOR 2 FAN SWITCH AUTO L2 L1 (HOT) W2 T6031 REFRIGERATION TEMPERATURE CONTROLLER E FALL ON H1 EM. HT. LED (RED) 4 EM. HT. RELAY CONTACT 1 EM. HT. X 2 H2 ANTICIPATOR 6 SYSTEM SWITCH OFF EM. HT. RELAY A COMPRESSOR CONTACTOR COMP. FAULT LED (YELLOW) H2 EM. HT. FALL H 8 HEAT Y Y G G R COM AUTO 9 SEQUENTIAL RELAY R8233B COOL W EH H1 ANTICIPATOR RISE CO O O FAN 10 C DF RS FAN C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HEAT(FASTER RESPONSE). RISE L1 L2 (HOT) REVERSING SOLENOID Fig. 154. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485—8 164 M2858 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE H1 ANTICIPATOR R 2 RTD1 L1 (HOT) OTD1 FAN SWITCH L2 1 3 EHR1 AUTO RTD2 2 FALL H1 W3 ON 4 ODT2 W2 H2 ANTICIPATOR EHR2 RTD3 5 H2 FALL 6 AUX. HT. LED (GRN) SYSTEM SWITCH RTD1 X OFF SYSTEM MONITOR 8 COOL 9 RISE C1 ANTICIPATOR CHANGEOVER EM. HT. LED (RED) AUTO FAN RELAY L G HEAT RD COOL CHANGEOVER VALVE EM. HT. 10 O RISE EM. HT. RELAY C1 E LACO COMPRESSOR CONTACTOR CHP Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 W3 TERMINAL ON SELECT MODELS. M1589 Fig. 155. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 165 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) 1 COOL CHANGEOVER VALVE H1 ANTICIPATOR FALL O 1 FAN SWITCH ON H1 FAN RELAY 2 G ON R 4 FALL AUX. HT. RELAY CONTACT OUTDOOR THERMOSTAT EM. HT. RELAY E H2 H2 ANTICIPATOR 6 RISE 8 SYSTEM SWITCH OFF L1 CO 9 HEAT X AUTO C1 ANTICIPATOR EM. HT. LED (GREEN) COOL 10 RISE COMPRESSOR FAILURE EM. HT. LED (RED) EM. HT. AUX. HT. RELAY W2 COMPRESSOR CONTACTOR C1 1 Y POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5720 Fig. 156. Schematic and hookup of T874G with Q674F. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS COOL CHANGEOVER VALVE 1 Y1 L1 (HOT) FAN SWITCH FALL 2 H1 L2 FAN RELAY AUTO G H1 ANTICIPATOR ON 3 R 4 CHECK LED (GREEN) DEFROST RELAY TIME DELAY RELAY 2 X H2 ANTICIPATOR FALL 6 W2 H2 SYSTEM SWITCH 8 RISE 9 C1 ANTICIPATOR 10 E OFF EM. HT. LED (RED) EM. HT. C1 CO TIME DELAY RELAY 1 LOCKOUT RELAY HEAT AUTO HI PRESSURE SWITCH COOL COMPRESSOR CONTACTOR W1 C1 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 157. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485—8 166 M2860 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 1 O H1 ANTICIPATOR COOL CHANGEOVER VALVE 2 H1 E FAN SWITCH EM. HT. RELAY AUTO G FALL ON 2 4 FAN RELAY B R HEAT CHANGEOVER VALVE H2 W2 6 H2 ANTICIPATOR FALL SYSTEM SWITCH OFF AUX. HT. RELAY L1 8 EM. HT. AUTO C1 ANTICIPATOR 9 C1 1 RISE COMPRESSOR FAILURE EM. HT. LED (RED) HEAT CO RISE X COOL AUX. HT. LED (GREEN) Y 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 2 B TERMINAL ON SELECT MODELS. M5721 Fig. 158. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 167 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE O 1 H1 ANTICIPATOR L1 L2 (HOT) 1 FAN RELAY G FAN SWITCH HEAT RELAY CONTACT AUTO 2 OFF R H1 FALL AUX. HT. RELAY 4 6 FALL H2 W OUTDOOR THERMOSTAT SYSTEM SWITCH E HEAT RELAY CONTACT H2 ANTICIPATOR EM. HT. RELAY 8 EM.HT. RISE 9 CO EM. HT. LED (RED) AUTO X OFF COMPRESSOR CONTACTOR LIMIT C1 ANTICIPATOR Y 10 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. C1 M5722 Fig. 159. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE O FALL 2 H1 SYSTEM COMPONENTS COOL CHANGEOVER VALVE FAN SWITCH H1 ANTICIPATOR AUTO 3 G FAN RELAY ON R 4 L2 H2 ANTICIPATOR FALL L1 (HOT) 5 1 W AUX. HT. RELAY H2 6 RISE SYSTEM SWITCH CO X EM. HT. RELAY 8 EM. HT. EM. HT. LED (RED) AUTO B 9 COMPRESSOR CONTACTOR OFF C1 ANTICIPATOR RISE Y 10 C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 160. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 60-2485—8 168 M5723 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE 1 L1 (HOT) L2 O 1 H1 ANTICIPATOR FAN SWITCH AUTO G ON 2 FAN RELAY R H1 OUTDOOR THERMOSTAT FALL W2 4 EM. HT. RELAY 1 H2 6 EM. HT. RELAY EM. HT. RELAY 2 CONTACT 1 H2 ANTICIPATOR FALL SYSTEM SWITCH E 2 8 EM. HT. RELAY CONTACT 2 EM.HT. RELAY 3 CO L C1 ANTICIPATOR SUPL. HT. RISE 9 SUPL. HT. LED (RED) ON C COMPRESSOR CONTACTOR 1 OFF C1 RISE Y 10 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 N.O. SWITCH — INSTALLER ADDED, TO LIGHT EM. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL. M5724 Fig. 161. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 169 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THEROMSTAT SUBBASE SYSTEM COMPONENTS C815A OUTDOOR THERMISTOR T 1 FAN RELAY FALL FAN SWITCH G H1 2 AUTO COOL CHANGEOVER VALVE ON H1 ANTICIPATOR O 3 R 1 4 FALL L1 (HOT) L2 H2 OUTDOOR THERMOSTAT 5 X2 AUX. HT. LED (GREEN) RESET HEATER 6 SYSTEM SWITCH RISE 8 EM. HT. B AUTO CO EM. HT. LED (RED) OFF C1 Y 10 C1 ANTICIPATOR 1 EM. HT. RELAY F 9 RISE AUX. HT. RELAY W COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 162. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 60-2485—8 170 M5725 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L2 L1 (HOT) HEAT DAMPER 1 B H1 ANTICIPATOR HEAT RELAY 1 W1 1 FAN SWITCH FAN RELAY H1 AUTO FALL 4 G ON H2 ANTICIPATOR HEAT RELAY 2 6 1 AUTO 8 H2 FALL SYSTEM SWITCH 9 W2 R OFF RESET S1 1 CO RESET CIRCUIT COOL CHANAGEOVER VALVE O FALL 10 S2 C1 ANTICIPATOR RESET CIRCUIT C1 Y RISE SERVICE LED (RED) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 H2 HAS 10¡F FIXED SETBACK FROM H1 ON T874G1485, 0-12¡F ADJUSTABLE ON T874G1535. 3 RESET IN MOMENTARY POSITION, SPRING RETURN TO OFF UPON SWITCH RELEASE. COMPRESSOR RELAY X ON LED (YELLOW) A M1820C C Fig. 163. Schematic and hookup of T874G with Q674C. Used in standard applications. 171 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 H1 ANTICIPATOR 2 O COOL CHANGEOVER VALVE FALL 3 Y FAN SWITCH H1 COMPRESSOR CONTACTOR AUTO G 4 ON R 6 FAN RELAY RISE 2 SYSTEM SWITCH 8 CO L MALFUNCTION LED (RED) OFF 9 C1 ANTICIPATOR RISE AUTO X 10 C1 HEAT CHANGEOVER VALVE B 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 R-L JUMPER SUPPLIED BY HONEYWELL. MALFUNCTION SWITCH M5726 Fig. 164. Schematic and hookup of T874H with Q674C. Used in standard applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 (HOT) L2 1 1 FALL H1 3 J 2 R1 N.O.2 S1 RELAY SOLENOID RELAY S1 N.C. H1 ANTICIPATOR 3 4 S FAN SWITCH 2 AUTO G ON H2 ANTICIPATOR R 5 C H2 H2 FALL FAN RELAY AUX. HT. RELAY 7 R1 N.C.1 8 SYSTEM SWITCH COMPRESSOR CONTACTOR H1 OFF R2 N.O. 1 AUTO REV. VALVE 9 3 C1 RISE 1 C1 ANTICIPATOR 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. R1 RELAY O 2 FIELD REMOVABLE JUMPER. 3 H1 AND C1 ARE DPST SWITCHES. Fig. 165. Schematic and hookup of T874L with Q674C. Used in heat pump applications. 60-2485—8 172 M5727 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) 1 L2 FALL FAN SWITCH H1 1 H1 ANTICIPATOR AUTO W1 ON HEAT RELAY 1 AUX. HT. LED (GREEN) 4 EM. HT. LED (RED) X W2 FALL 6 HEAT RELAY 2 H2 RH SYSTEM SWITCH H2 ANTICIPATOR L 8 OFF SYSTEM MONITOR EM. HT. RISE HEAT C1 9 EM. HT. RELAY E AUTO G FAN RELAY COOL 10 RC COMRESSOR CONTACTOR 1 C1 ANTICIPATOR Y1 C2 ANTICIPATOR COMRESSOR CONTACTOR 2 11 Y2 RISE C2 L2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5728 1 L1 (HOT) Fig. 166. Schematic and hookup of T874D with Q674F. Used in standard applications. 173 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L2 (HOT) L1 1 R ODT 1 H1 ANTICIPATOR 2 FALL RTD 1 H1 3 4 RTD 2 FAN SWITCH ODT 2 AUTO EHR 2 ON H2 ANTICIPATOR 5 H2 EHR 1 RTD 3 W2 RTD 1 AUX. HT. LED (GREEN) FALL X SYSTEM SWITCH EM. HT. LED (RED) COMPRESSOR FAILURE RD OFF L 7 FALL CHANGEOVER 8 EM. HT. HEAT G AUTO B FAN RELAY HEAT CHANGEOVER VALVE COOL 9 EM. HT. RELAY E C1 ANTICIPATOR 10 EHT1 CHP LACO Y COMPRESSOR CONTACTOR C1 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 167. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485—8 174 M1592A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS W3 W3 RELAY O COOL CHANGEOVER VALVE L H1 ANTICIPATOR 1 FAN SWITCH COMPRESSOR MONITOR FAN RELAY G AUTO ON C ANTICIPATOR L1 (HOT) L2 R 2 1 W2 H1 C 4 5 H2 ANTICIPATOR H2 EM. HT. LED (RED) 3 FALL SYSTEM SWITCH E EM. HT. RELAY EM. HT. HEAT 6 AUX. HT. LED (GRN) AUX. HT. RELAY OFF FALL COOL X 3 X2 HEAT CHANGEOVER VALVE B 11 W1 RELAY 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. W1 2 REMOVE JUMPER WHEN W1 RELAY IS USED. 2 3 FACTORY-INSTALLED JUMPER. COMPRESSOR RELAY Y M5067 Fig. 168. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 175 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 1 FALL H1 ANTICIPATOR SYSTEM COMPONENTS O FAN SWITCH COOL CHANGEOVER VALVE AUTO 2 G ON FAN RELAY H1 B 3 B RELAY W3 4 AUX HT. RELAY SYSTEM SWITCH H2 ANTICIPATOR L2 E OFF HEAT EM. HT. RELAY EM. HT. LED (RED) AUTO X 2 COOL 8 C1 1 L EM. HT. H2 FALL RISE AUX. HT. LED (GREEN) AUX. HT. RELAY 9 W2 C1 ANTICIPATOR Y 10 CO 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 12 2 TERMINAL LABELED C/X ON SOME MODELS. 3 W3 TERMINAL ON SOME MODELS ONLY. RISE COMPRESSOR CONTACTOR M5986A Fig. 169. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485—8 L1 (HOT) R 6 176 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS W3 W1 RELAY W3 RELAY W1 2 H1 FALL H1 ANTICIPATOR B RELAY FAN SWITCH B 3 FAN RELAY AUTO G 4 L1 (HOT) ON R 5 AUX. HT. RELAY 6 H2 ANTICIPATOR SYSTEM SWITCH AUX. HT. LED (GREEN) OFF EM. HT. H2 X 3 HEAT 8 FALL 9 CO C1 ANTICIPATOR L2 1 W2 EM. HT. LED (RED) AUTO COOL L E RISE 10 RISE O C1 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1. 3 EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION. COMPRESSOR FAULT COOL CHANGEOVER VALVE EM. HT. RELAY COMPRESSOR CONTACTOR Y M5987A Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 177 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 (HOT) L2 R 2 1 FALL H1 Y FAN SWITCH 3 H1 ANTICIPATOR O.D.T. COMPRESSOR CONTACTOR AUTO G 4 ON FAN RELAY H2 ANTICIPATOR EM. HT. LED (RED) FALL H2 HCR1 W1 5 HCR1 6 F 8 C 9 E HCR2 2 CO SYSTEM SWITCH RISE C1 ANTICIPATOR HCR2 X EM. HT. 10 "X" RELAY AUTO "P" RELAY OFF P 11 C1 RISE CO HCR3 O 12 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 EXTERNAL JUMPER SUPPLIED BY HONEYWELL. COOL CHANGEOVER VALVE M5729 Fig. 171. Schematic and hookup of T874J with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE 2 H1 ANTICIPATOR SYSTEM COMPONENTS FAN SWITCH FAN RELAY AUTO G 3 ON R 4 O FALL FAULT LED (RED) H1 RISE SYSTEM SWITCH CO COOL CHANGEOVER VALVE C 8 C1 ANTICIPATOR 2 CHECK FILTER 3 LED (YELLOW) 9 HEAT 10 L1 (HOT) L2 1 OFF COOL 11 12 Y C1 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR Fig. 172. Schematic and hookup of T874H with Q674B. Used in heat pump applications. 60-2485—8 178 M1401 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH 2 FAN RELAY H1 ANTICIPATOR AUTO G 3 ON R 4 O FALL FAULT LED (RED) H1 C 8 RISE COOL CHANGEOVER VALVE 2 C1 ANTICIPATOR SYSTEM SWITCH CO CHECK FILTER 3 LED (YELLOW) 9 OFF 10 L1 (HOT) L2 1 AUTO 11 12 Y C1 1 RISE COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M1400 Fig. 173. Schematic and hookup of T874H with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 HA 2 FAN SWITCH 3 FAN RELAY AUTO G H1 ON EM.. HT. RELAY FALL H2 4 X2 5 T ODA C815A OUTDOOR THERMISTOR FALL 1 L1 (HOT) L2 R 6 "F" RELAY C1 8 F SYSTEM SWITCH AUX. HT. RELAY EM. HT. RISE 9 W AUTO EM. HT. LED (RED) OFF 2 CA U 10 AUX. HT. LED (GREEN) C2 B COOL CHANGEOVER VALVE RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVABLE JUMPER. O COMPRESSOR CONTACTOR Y M1403 Fig. 174. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 179 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS H1 ANTICIPATOR 1 O FAN SWITCH 2 FAN RELAY ON COOL CHANGEOVER VALVE G AUTO FALL L1 (HOT) R L2 1 4 H2 ANTICIPATOR H.C.R. 1 O.D.T. W2 6 H.C.R. 1 H.C.R.2 H.C.R. 2 H.C.R.3 FALL 8 SYSTEM SWITCH E C1 ANTICIPATOR SUPL. HT. 9 L ON CO RISE MANUAL (RED) AUTO (YEL) OFF C 10 Y HEAT PUMP (GRN) C1 RISE DEFROST (RED) COMPRESSOR CONTACTOR D 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2112A Fig. 175. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE 2 FALL SYSTEM COMPONENTS Y1 COOL CHANGEOVER VALVE H1 ANTICIPATOR H1 3 Y2 COMPRESSOR CONTACTOR 4 AUTO FALL G ON SETBACK 2 FAN RELAY OPEN-NIGHT CLOSED-DAY FAN SWITCH 6 SYSTEM SWITCH RISE 8 L2 1 L1 (HOT) R SETBACK RELAY OFF L CO 9 AUTO X1 LED 10 C 3 RISE LED C1 ANTICIPATOR X2 C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 SETBACK STAGE OFFSET 12°F (7°C) FROM H1 STAGE. 3 LEDS ON SOME MODELS. M5730 Fig. 176. Schematic and hookup of T874G with Q674C. Used in standard applications. 60-2485—8 180 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS LOCKOUT (RESET) RELAY H1 ANTICIPATOR FAN SWITCH 1 X RESET LED (RED) AUTO G H1 ON FALL FAN RELAY 4 3 L1 (HOT) L2 R1 6 SYSTEM SWITCH H2 1 R2 OFF FALL AUTO 7 2 B CO 8 RISE 2 HEAT CHANGEOVER VALVE O COOL CHANGEOVER VALVE 9 Y C1 ANTICIPATOR 10 C1 RISE 1 COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 USE EITHER 'B' OR 'O' ONLY FOR SYSTEM CHANGEOVER. 0.8A AT 30 VAC MAXIMUM LOAD CURRENT. 3 SECOND STAGE HEAT MAKES 12oF (7oC) AFTER FIRST STAGE HEAT TO PROVIDE SETBACK M114C Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL CHANGEOVER RELAY H1 W1 1 FAN SWITCH H1 ANTICIPATOR AUX.HT. RELAY 3 W2 AUTO ON R 4 L1 (HOT) 1 L2 L 6 FALL H2 H2 ANTICIPATOR SERVICE LED (RED) SYSTEM SWITCH OFF 8 X COOL EM, HT. LED (YELLOW) C0 AUTO RISE 9 C1 ANTICIPATOR FAN RELAY G HEAT EM.HT. COMPRESSOR RELAY 10 C EM.HT. RELAY K 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M18623 Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications. 181 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS W1 1 DEFROST RELAY H1 ANTICIPATOR OUTDOOR THERMOSTAT REVERSING VALVE HEAT RELAY 2 EM.HT. RELAY CONTACT 2 EM.HT. RELAY CONTACT HEAT RELAY 3 H1 W3 FALL 4 FAN SWITCH FAN RELAY H2 ANTICIPATOR AUTO G ON 5 1 L1 (HOT) L2 R H2 FALL 6 W2 SYSTEM SWITCH OFF EM. HT. LED (RED) EM. HT. RELAY X EM. HT. CHECK LED (GREEN) 8 HEAT OPTIONAL COMPRESSOR FAILURE DEVICE L RISE 9 C1 ANTICIPATOR C1 AUTO HIGH PRESSURE SWITCH COOL CO COMPRESSOR CONTACTOR Y 10 1 HEAT RELAY 1 E POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 179. Schematic and hookup of T874N with Q674F. Used in heat pump applications. 60-2485—8 182 M3686 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) FAN DELAY RELAY 1 CHANGEOVER VALVE ELEC. HT. RELAY STG. 1 L2 R-11 R-11 FALL 1 W1 H1 R-10 H1 ANTICIPATOR R-8 R-6 OVERLOAD Y1 FAN SWITCH FAN RELAY AUTO G ON R-6 R-1 R-2 4 FALL R H1 H2 ANTICIPATOR COMPRESSOR CONTACTOR R-10 6 W2 8 EM. HT. LED (RED) ELEC. HT. RELAY STG. 2 E C1 X2 SYSTEM SWITCH RISE RISE 10 R-5 2 9 C1 ANTICIPATOR EM. HT. AUTO EM. HT. RELAY R-6 FILTER LED (YELLOW) RANDOM START R-8 (OPT.) OFF 11 (HEAT PUMP OPERATION) R-10 R-5 C2 ANTICIPATOR C2 T2 Y2 (BIOLERLESS OPERATION ) R-11 R-3 X1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FILTER LED ON SOME MODELS. M5957 Fig. 180. Schematic and hookup of T874A,D with Q674J. Used in heat pump applications. 183 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENT L1 2 TIME CLOCK CO 3 H2 L2 (HOT) FALL 1 Y FALL COMPRESSOR RELAY FAN SWITCH 4 AUTO G ON FALL FAN RELAY 6 H1 ANTICIPATOR H1 R W 8 RISE REVERSING VALVE W2 SYSTEM SWITCH C1 9 C1 ANTICIPATOR COMPRESSOR FAULT LED (RED) OFF 10 COMPRESSOR FAULT A AUTO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M18587 Fig. 181. Schematic and hookup of T874K with Q674C. Used in heat pump applications. THERMOSTAT H1/C ANTICIPATOR SUBBASE 1 T 2 H1 FALL SYSTEM COMPONENTS FAN SWITCH H2 ANTICIPATOR 3 W2 AUTO OUTDOOR RESET AUX. HT. FAN G 4 ON R 5 RESET 6 H2 FALL E SYSTEM SWITCH EM. HT. W89 HEAT PUMP CONTROL PANEL B EM. HT. EM. HT. LED (YELLOW) HEAT EM. HT. LIGHT X SERVICE LED (RED) OFF COOL L SERVICE LIGHT COOL/HEAT O Y COMPRESSOR M3951 Fig. 182. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 184 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE O 1 H1 ANTICIPATOR FALL SYSTEM COMPONENTS 2 H1 COOL CHANGEOVER VALVE FAN SWITCH AUTO G ON 2BH FAN RELAY 4 R H2 ANTICIPATOR O. D. S. FALL 1BH SH 6 H2 E SYSTEM SWITCH RISE L1 8 EM. HT. LED (RED) CO C1 ANTICIPATOR 9 X EM. HT. AUX. HT. LED (GREEN) ON 10 COMPRESSOR FAILURE 1BH W OFF RISE Y C1 COMPRESSOR CONTACTOR 1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. L1 L2 (HOT) M3950 Fig. 183. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 1 FALL H1 NO FAN SWITCH W1 W2 4 H2 ANTICIPATOR FALL H2 1 HEAT RELAY 2 L2 RH L1 (HOT) RC L1 (HOT) 6 SYSTEM SWITCH RISE C1 9 C1 ANTICIPATOR C2 ANTICIPATOR OFF 1 COMPRESSOR CONTACTOR 1 AUTO 10 Y1 Y2 11 RISE C2 L2 1 8 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 2 M3953 Fig. 184. Schematic and hookup of T874A,F with Q674G. Used in standard applications. 185 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) H1 ANTICIPATOR HEAT RELAY 1 1 W1 FALL AUTO FAN SWITCH H1 G ON FAN RELAY RC W2 4 HEAT RELAY 2 H2 ANTICIPATOR FALL SYSTEM SWITCH 6 H2 RH IGNITION RELAY OFF RISE C1 8 HEAT 9 AUTO C1 ANTICIPATOR 10 B COMPRESSOR CONTACTOR 1 COOL C2 ANTICIPATOR RISE Y1 Y2 11 COMPRESSOR CONTACTOR 2 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 L1 L2 (HOT) M3954 Fig. 185. Schematic and hookup of T874D with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 H1 ANTICIPATOR 1 FALL H2 5 NO FAN SWITCH 7 C2 L1 (HOT) 8 W2 SYSTEM SWITCH OFF FAN RELAY B AUTO FAN RELAY 9 O 10 RC 11 Y2 C1 ANTICIPATOR RISE L2 RH HEAT RELAY 2 6 RISE C1 1 HEAT RELAY 1 4 H2 ANTICIPATOR W1 C2 ANTICIPATOR L2 L1 (HOT) 1 COMPRESSOR CONTACTOR 2 12 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 M3955 Fig. 186. Schematic and hookup of T874D with Q674G. Used in standard applications. 60-2485—8 186 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS R4 FALL HEAT RELAY 2 H1 R3 2 FAN SWITCH H1 ANTICIPATOR HEAT RELAY 1 R2 HIGH 3 HI SPEED FAN RELAY LOW R1 4 H2 ANTICIPATOR C HIGH TEMP. SWITCH HIGH PRESSURE SWITCH LO SPEED FAN RELAY LR COOL CONTACTOR LOCKOUT RELAY 5 R5 FALL H2 SYSTEM SWITCH RISE C1 8 X 1 L2 HEAT R L1 (HOT) OFF C1 ANTICIPATOR COOL 1 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS M3956 AND OVERLOAD PROTECTION AS REQUIRED. Fig. 187. Schematic and hookup of T874C with Q674B. Used in standard applications. THERMOSTAT FALL SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 1 W1 H1 1 4 5 FALL H2 ANTICIPATOR L2 NO FAN SWITCH 6 H2 RH L1 (HOT) HEAT RELAY 2 W2 T 7 RISE C1 8 SYSTEM SWITCH 9 AUTO B O C1 ANTICIPATOR 10 RISE C2 FAN RELAY C2 ANTICIPATOR L2 RC 11 L1 (HOT) 1 Y2 COMPRESSOR CONTACTOR 2 12 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 M3958 Fig. 188. Schematic and hookup of T874D with Q674G. Used in standard applications. 187 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 1 B W1 4 5 FALL M839 MOTOR NO FAN SWITCH ANTICIPATOR H2 L1 6 W2 Y RH R L2 NO SYSTEM SWITCH RC 8 Y2 9 Y1 10 11 M3960 Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS V 2 1 VR RESET OG H1 ANTICIPATOR FALL H1 2 IN STAT 1 M FAN SWITCH L1 (HOT) COMPRESSOR CONTACTOR L2 AUTO 3 HI PR F SERVICE RELAY ON 4 L1 (HOT) FAN RELAY L 5 H2 ANTICIPATOR SERVICE LED (RED) H2 6 FALL L2 3 O. D. S. EM. HT. EM. HT. RELAY 1 ELEC. HT. RELAY Y 7 RISE C1 E SYSTEM SWITCH C1 ANTICIPATOR ELEC. HT. RELAY EM. HT. LED (YELLOW) 8 EM. HT. X HEAT 10 A OFF C815A OUTDOOR THERMISTOR COOL R 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. 3 WIRE JUMPER FOR SERVICE LIGHT. COOL CHANGEOVER VALVE M3978 Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications. 60-2485—8 188 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 2 FALL H1 C1 H1/C1 ANTICIPATOR 3 SYSTEM COMPONENTS FAN SWITCH Z AUTO LO O "Z" RELAY COOL CHANGEOVER VALVE HI G CONT. L2 FAN RELAY R 4 H2 ANTICIPATOR FALL AUX. HT. RELAY 6 H2 L1 (HOT) 1 W2 C SYSTEM SWITCH W1 HEAT RELAY HEAT OFF COOL COOL RELAY Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3965 Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications. THERMOSTAT FALL SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 W1 1 H1 SYSTEM SWITCH OFF 4 FALL H2 ANTICIPATOR AUTO HEAT RELAY 2 6 H2 W2 FILTER LED (YELLOW) RISE C1 8 X SERVICE LED (RED) FAN SWITCH AUTO A G ON 9 R 2 O C1 ANTICIPATOR 10 O L2 FAN RELAY L1 (HOT) MOMENTARY CIRCUIT 1 COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR Y1 Y2 11 RISE C2 COMPRESSOR CONTACTOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. M3959 Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications. 189 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT H1 ANTICIPATOR FAN SWITCH 1 L1 (HOT) L2 RH AUTO FALL W1 H1 ON 1 HEAT RELAY 1 4 W2 6 B HEAT RELAY 2 H2 FALL H2 ANTICIPATOR CHANGEOVER RELAY (HEAT) O SYSTEM SWITCH 8 RISE G HEAT C1 CHANGEOVER RELAY (COOL) 2 OFF FAN RELAY 9 AUTO Y2 COOL COMPRESSOR CONTACTOR 2 10 C1 ANTICIPATOR Y1 C2 ANTICIPATOR 11 RC C2 RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 JUMPER RH, RC FOR SINGLE TRANSFORMER. 1 COMPRESSOR CONTACTOR 1 L2 L1 (HOT) M3203B Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 H1 ANTICIPATOR Y1 AUTO 3 G ON R FAN SWITCH CHECK LED (GREEN) 4 FALL DR TDR 2 X H2 ANTICIPATOR H2 COOL FAN RELAY CHANGEOVER VALVE HBTH W2 6 TDR 1 SYSTEM SWITCH E OFF RISE C 8 EM. HT. EM. HT. LED (RED) CO C1 ANTICIPATOR 9 10 COMPRESSOR CONTACTOR HEAT W1 AUTO HPA COOL 1 RISE C1 L1 L2 (HOT) 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 60-2485—8 190 M3977 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 1 COOL CHANGEOVER VALVE H1 ANTICIPATOR O 1 H1 FAN SWITCH FAN RELAY FALL 2 G AUTO "B" RELAY ON B 4 R H2 H2 ANTICIPATOR FALL 6 SYSTEM SWITCH EM. HT. RELAY E OFF 8 L EM. HT. CO RISE HEAT 9 C1 ANTICIPATOR AUTO COOL EM. HT. LED (RED) X AUX. HT. LED (GREEN) 10 W2 AUX. HT. RELAY Y COMPRESSOR CONTACTOR C1 RISE 1 COMPRESSOR FAULT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2974 Fig. 195. Schematic and hookup of T874G with Q674F. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS COOL CHANGEOVER VALVE H1 ANTICIPATOR O 1 H1 FAN SWITCH FALL 2 L1 (HOT) L2 1 FAN RELAY G AUTO ON R H.C.R.1 4 W2 H2 H2 ANTICIPATOR FALL O.D.T. 6 E 8 SYSTEM SWITCH H.C.R.1 H.C.R.2 H.C.R.2 H.C.R.3 CO RISE SUPL. HT. 9 C1 ANTICIPATOR ON OFF L SUPL. HT. LED (RED) C 10 Y RISE C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M2975 Fig. 196. Schematic and hookup of T874G with Q674J. Used in heat pump applications. 191 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS G 1 FAN RELAY W 2 AUTO H1 AUX. HT. LED (GREEN) U 2 AUX. HEATER RELAY ON C1 B 3 FALL FAN SWITCH EM. HT. LED (RED) COMPRESSOR MONITOR F 1 4 L1 (HOT) L2 R H2 5 FALL SYSTEM SWITCH T EM. HT. 6 HEAT OUTDOOR THERMISTOR X2 OFF 11 OUTDOOR THERMOSTAT COOL O 1 COMPRESSOR RELAY POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE Y M2970 2 FIELD REMOVABLE JUMPER. Fig. 197. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 STAGE 1 HEAT RELAY W1 1 H1 FAN SWITCH FALL COMPRESSOR CONTACTOR AUTO H1 ANTICIPATOR 3 Y1 ON FAN RELAY 4 G H2 FALL H2 ANTICIPATOR 6 R 7 RISE C1 OFF 8 STAGE 2 HEAT RELAY SYSTEM SWITCH W2 HEAT AUTO 9 COOL 10 C2 ANTICIPATOR M2976 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 198. Schematic and hookup of T874L with Q674E. Used in standard applications. 60-2485—8 192 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT L1 (HOT) L2 1 W3 RELAY H1 ANTICIPATOR 2 W3 FAN SWITCH FAN RELAY H1 AUTO FALL G 3 ON R 4 H2 W2 H2 ANTICIPATOR FALL 5 AUX. HT. RELAY SYSTEM SWITCH AUX. HT. LED (GREEN) EM. HT. RELAY E EM. HT. LED (RED) OFF COMPRESSOR FAULT 8 CO EM. HT. RISE CHECK LED (RED) 9 HEAT 10 COOL AUTO B C1 ANTICIPATOR C1 L X HEAT CHANGEOVER VALVE 11 O RISE COOL CHANGEOVER RELAY 12 Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M2977 Fig. 199. Schematic and hookup of T874G with Q674F. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 T 1 H1 C1 H2 ANTICIPATOR OUTDOOR THERMOSTAT FAN SWITCH RISE 2 AUTO 3 ON OUTDOOR THERMOSTAT 4 FALL FAN RELAY G 5 H2 C1 ANTICIPATOR 6 SYSTEM SWITCH SERVICE LED (YELLOW) EM. HT. COOL SEQ 1 K COMPRESSOR CONTACTOR EM. HT. LED (RED) Y 12 W1 1 SERVICE Z OFF H1 ANTICIPATOR R X HEAT 11 SEQ 2 W2 HEAT CHANGEOVER VALVE POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2978 Fig. 200. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 193 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT C1 1 H2 ANTICIPATOR RISE T OUTDOOR THERMOSTAT FAN SWITCH 2 AUTO 3 ON OUTDOOR THERMOSTAT FAN RELAY G 5 H2 SERVICE LED (YELLOW) C1 ANTICIPATOR SYSTEM SWITCH 6 EM. HEAT 11 R X HEAT SERVICE Z OFF K COMPRESSOR CONTACTOR EM. HT. LED (RED) COOL H1 ANTICIPATOR SEQ 1 Y 12 HEAT CHANGEOVER VALVE W1 1 SEQ 2 W2 4 RISE L1 (HOT) L2 1 C815A OUTDOOR THERMISTOR RESET H1 SYSTEM COMPONENTS POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2979 Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS A2 H1 SERVICE LED (RED) FALL HEAT RELAY 1 W1 1 H1 ANTICIPATOR L1 (HOT) L2 1 SERVICE LED (RED) 4 5 NO FAN SWITCH A1 HEAT RELAY 2 H2 H2 ANTICIPATOR FALL 6 W2 "T" RELAY 7 T C1 RISE 8 9 RC SYSTEM SWITCH FAN RELAY B B OFF 10 C1 ANTICIPATOR RISE RH AUTO FAN RELAY O 11 O 12 Y2 C2 C2 ANTICIPATOR 1 L1 (HOT) L2 COMPRESSOR CONTACTOR 2 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR 1 Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications. 60-2485—8 194 M2980 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS COMPRESSOR CONTACTOR Y CO L1 (HOT) L2 1 FAN SWITCH FALL FAN RELAY 2 3 AUTO G ON R HEAT CHANGEOVER VALVE 4 W H1 6 H1 ANTICIPATOR FALL SYSTEM SWITCH COMP. FAULT (RED) 8 OFF C1 RISE W2 9 COMPRESSOR FAULT A AUTO 10 C1 ANTICIPATOR 1 M2981 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE HEAT RELAY 1 1 H1 FALL W1 FAN SWITCH HEAT RELAY 2 AUTO H1 ANTICIPATOR L1 (HOT) L2 1 W2 ON R 4 LED (RED) H2 X B H2 ANTICIPATOR FALL 6 8 EM. HT. RELAY SYSTEM SWITCH OFF E FAN RELAY G C1 RISE EM. HT. 9 COMPRESSOR CONTACTOR 2 HEAT AUTO Y2 10 C2 ANTICIPATOR C2 COMPRESSOR CONTACTOR 1 COOL C1 ANTICIPATOR RISE 2 Y1 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 LED IS NOT LABELED. JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION. JUMPER E TO X FOR EMERGENCY HEAT INDICATION. CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM NEEDS TO BE CHECKED. M2982A Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications. 195 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 COOL CHANGEOVER VALVE H1 ANTICIPATOR 2 Y1 H1 COMPRESSOR CONTACTOR FALL 3 Y2 FAN SWITCH FAN RELAY AUTO 4 G ON R 6 L 8 CO RISE SYSTEM SWITCH LED (RED) X1 OFF 9 C AUTO C1 ANTICIPATOR C1 RISE LED (RED) 10 2 X2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 LEDS ON SOME MODELS. M2983 Fig. 205. Schematic and hookup of T874H with Q674C. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS R 2 H1 H1 ANTICIPATOR FALL FAN SWITCH COMPRESSOR CONTACTOR L1 (HOT) L2 1 Y 3 AUTO 4 ON FAN RELAY H2 ANTICIPATOR G H.C.R.1 5 H2 W2 FALL 6 8 CO RISE SYSTEM SWITCH SUPL. HT. LED (RED) L O.D.T. SUPL. HT. 9 C1 ANTICIPATOR 10 ON C OFF E H.C.R.1 H.C.R.2 H.C.R.2 H.C.R.3 11 O 12 RISE C1 CO 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE Fig. 206. Schematic and hookup of T874J with Q674J. Used in heat pump applications. 60-2485—8 196 M2984 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS R 2 H1 FAN SWITCH H1 ANTICIPATOR FALL L1 (HOT) L2 1 COMPRESSOR CONTACTOR Y 3 AUTO 4 ON FAN RELAY H2 ANTICIPATOR G H.C.R.1 5 H2 W2 FALL 6 CO RISE SUPL. HT. LED (RED) SYSTEM SWITCH 8 O.D.T. L SUPL. HT. 9 C1 ANTICIPATOR 10 HEAT C OFF E COOL H.C.R.1 H.C.R.2 H.C.R.2 H.C.R.3 11 O 12 RISE 1 CO C1 COOL CHANGEOVER VALVE POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2985 Fig. 207. Schematic and hookup of T874J with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS HEAT RELAY 1 W1 1 H1 HEAT RELAY 2 FALL NO FAN SWITCH H1 ANTICIPATOR L1 (HOT) L2 1 W2 RH 4 2 5 H2 RC H2 ANTICIPATOR FALL 6 Y2 1 8 COMPRESSOR CONTACTOR 2 C1 RISE Y1 9 NO SYSTEM SWITCH L1 (HOT) L2 COMPRESSOR CONTACTOR 1 10 C1 ANTICIPATOR C2 ANTICIPATOR RISE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 RC-RH REMOVABLE JUMPER WHEN SPECIFIED. 11 M2986 C2 Fig. 208. Schematic and hookup of T874D with Q674D. Used in standard applications. 197 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS R EM. HT. RELAY EM. HT. LED (RED) H1 L C1 FAN SWITCH H1/C1 ANTICIPATOR RISE L1 (HOT) L2 1 2 AUTO 3 ON AUX. HT. LED (GREEN) X AUX. HT. RELAY W2 FAN RELAY 4 G 6 COOL CHANGEOVER VALVE SYSTEM SWITCH H2 ANTICIPATOR H2 EM. HEAT O EM. HT. RELAY HEAT FALL E OFF COMPRESSOR CONTACTOR COOL Y ’"B" RELAY M2987 B POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 1 Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS FAN RELAY H1 1 FALL H1 ANTICIPATOR 2 3 HCO G FAN SWITCH AUTO R ON HEAT CHANGEOVER VALVE FALL 4 H2 H2 ANTICIPATOR 6 8 SYSTEM SWITCH OFF FILTER B LED (YELLOW) F HEAT AUTO C1 RISE COOL CHANGEOVER VALVE O CCO FALL L1 (HOT) L2 1 COOL L RESET LED (RED) COMPRESSOR CONTACTOR 1 9 Y1 10 C1 ANTICIPATOR C2 ANTICIPATOR RISE C2 1 COMPRESSOR CONTACTOR 2 11 Y2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications. 60-2485—8 198 M2988 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 W1 RELAY H1 ANTICIPATOR 2 W1 FAN SWITCH H1 FALL FAN RELAY AUTO G 3 ON R AUX. HT. RELAY SYSTEM SWITCH 4 W2 AUX. HT. LED (GREEN) OFF H2 H2 ANTICIPATOR FALL 6 EM. HT. X HEAT 8 EM. HT. LED (RED) AUTO RISE C1 ANTICIPATOR C1 L COMPRESSOR FAULT COOL 10 Y1 1 COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M2989 Fig. 211. Schematic and hookup of T874G with Q674F. Used in standard applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS HEAT RELAY 1 L1 (HOT) L2 HEAT RELAY 2 1 W1 1 H1 FAN SWITCH FALL AUTO H1 ANTICIPATOR ON W2 RH 4 2 H2 RC H2 ANTICIPATOR FALL 6 FAN RELAY SYSTEM SWITCH 8 OFF C1 RISE G Y2 COMPRESSOR CONTACTOR 2 HEAT 9 AUTO COOL 10 Y1 1 COMPRESSOR CONTACTOR 1 L1 (HOT) L2 C1 ANTICIPATOR C2 ANTICIPATOR RISE C2 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 RC -RH REMOVABLE JUMPER WHEN SPECIFIED. M2990 Fig. 212. Schematic and hookup of T874A with Q674E. Used in standard applications. 199 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 1 2 H1 H1 ANTICIPATOR FALL SYSTEM SWITCH RELAY 1 N.O. 2 OFF H1 3 AUTO COMPRESSOR CONTACTOR 4 H2 R FALL C 7 8 FAN SWITCH FIELD REMOVABLE JUMPER AUX. HT. RELAY H2 LO CO 9 10 C1 ANTICIPATOR S1 RELAY N.C. Y 5 H2 ANTICIPATOR RISE S1 RELAY MED L CHECK LED (RED) R1 RELAY N.C. 1 COMPRESSOR CONTACTOR HIGH ON R2 RELAY N.O 1 COOL CHANGEOVER VALVE O R1 RELAY K1 RELAY 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. G1 K2 RELAY G2 M2991 Fig. 213. Schematic and hookup of T874L with Q674C. Used in heat pump applications. 60-2485—8 200 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT H1 SYSTEM COMPONENTS L1 (HOT) L2 1 1 FALL SYSTEM SWITCH HEAT H1 ANTICIPATOR 2 AUX. HT. RELAY H1 OFF R C1 ANTICIPATOR R1 RELAY COOL O 3 4 C1 RISE 5 COOL CHANGEOVER VALVE L FAN SWITCH R2 RELAY N.O. 1 LO COMPRESSOR CONTACTOR MED C HIGH CHECK LED (RED) ON COMPRESSOR CONTACTOR 11 S1 RELAY N.C. Y 12 1 K1 RELAY POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. G1 K2 RELAY G2 M2992 Fig. 214. Schematic and hookup of T874A with Q674B. Used in standard applications. 201 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) L2 1 1 2 H1 H1 ANTICIPATOR FALL SYSTEM SWITCH RELAY 1 N.O. 2 HEAT S1 RELAY H1 3 OFF COMPRESSOR CONTACTOR 4 S1 RELAY N.C. COOL H2 Y 5 H2 ANTICIPATOR R FALL C 7 8 FIELD REMOVABLE JUMPER FAN SWITCH AUX. HT. RELAY H2 LO RISE C1 9 10 C1 ANTICIPATOR L MED CHECK LED (RED) R1 RELAY N.C. 1 COMPRESSOR CONTACTOR HIGH ON R2 RELAY N.O. 1 11 COOL CHANGEOVER VALVE O R1 RELAY 12 K1 RELAY 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. G1 K2 RELAY G2 M2993 Fig. 215. Schematic and hookup of T874L with Q674B. Used in heat pump applications. 60-2485—8 202 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE O H1 ANTICIPATOR H1 FALL G FAN SWITCH 1 FAN RELAY L2 AUTO 1 L1 (HOT) ON 2 R 3R 4 SEQ 2 W1 6 FALL AUX. HT. LED (YELLOW) H2 SEQ 1 2 E H2 ANTICIPATOR SYSTEM SWITCH X RISE EM. HT. AUTO CO 9 OFF 5R C SYSTEM LED (GREEN) 10 RISE 4R CHECK LED (RED) 8 C1 EM. HT. RELAY 4R HPS C1 ANTICIPATOR 4R Y 1 COMPRESSOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CONTACTOR 2 REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS. 4R M1629 Fig. 216. Schematic and hookup of T874G with Q674J. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS D. P. HEAT CHANGEOVER VALVE W1 1 ODT H1 EHR 2 FALL HEAT CONTACTOR #2 H1 ANTICIPATOR EHR W3 4 HEAT CONTACTOR #3 FAN SWITCH H2 ANTICIPATOR 1 G AUTO 5 L2 FAN RELAY ON R L1 (HOT) HEAT CONTACTOR #1 H2 W2 6 FALL SYSTEM SWITCH X CHECK LED (GREEN) OFF OPTIONAL COMPRESSOR FAILURE 8 AUTO L C1 RISE CO C1 ANTICIPATOR 1 9 Y COMPRESSOR CONTACTOR 10 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5900 Fig. 217. Schematic and hookup of T874N with Q674C. Used in heat pump applications. 203 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SYSTEM COMPONENTS SUBBASE L1 (HOT) R L2 L 2 H1/C1 ANTICIPATOR 3 EM. HT. LED (RED) 3 FAN SWITCH C1 FALL 4 2 ON X H2 ANTICIPATOR H2 FALL AUX. HT. RELAY W3 AUTO H1 1 AUX. HT. LED (GRN) 6 AUX. HT. RELAY W2 SYSTEM SWITCH EM. HT. FAN RELAY G HEAT COOL CHANGEOVER VALVE OFF O COOL E EM. HT. RELAY Y COMPRESSOR CONTACTOR B 1 "B" RELAY POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 TERMINAL LABELED C/X ON SOME MODELS. 3 W3 TERMINAL AVAILABLE ON SOME MODELS ONLY. M3683A Fig. 218. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 204 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE 1 W1 H1 HEAT RELAY 1 2 FALL W2 H1 ANTICIPATOR HEAT RELAY 2 W3 SYSTEM SWITCH OFF 4 AUTO 5 Y2 6 A FALL H2 ANTICIPATOR 3 SERVICE LED (RED) 7 FAN SWITCH FAN RELAY G H2 AUTO C1 RISE 8 L1 (HOT) R ON L2 1 2 9 O MONENTARY CIRCUIT COMPRESSOR CONTACTOR 1 10 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. 3 H2 OFFSET 12oF FROM H1. M5901 Fig. 219. Schematic and hookup of T874C with Q674C. Used in standard applications. 205 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS CONTROL MODULE 1 HEAT RELAY #1 SYSTEM SWITCH H1 FALL OFF 2 H1 ANTICIPATOR W1 HEAT RELAY #2 W2 AUTO HEAT RELAY #3 4 W3 COMPRESSOR CONTACTOR #2 5 Y2 FALL H3 SYSTEM MONITOR H2 ANTICIPATOR H2 6 A SERVICE LED (RED) FALL FAN RELAY G 7 L2 RISE C1 8 FAN SWITCH AUTO ON 1 MOMENTARY CIRCUIT O 9 2 10 COMPRESSOR CONTACTOR #1 Y1 RISE C2 L1 (HOT) R 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE. M5929 Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications. THERMOSTAT SYSTEM COMPONENTS SUBBASE Y1 2 H1 ANTICIPATOR H1 3 COOL CHANGEOVER VALVE FAN SWITCH 1 AUTO FALL 4 G L2 FAN RELAY ON R L1 (HOT) COMPRESSOR CONTACTOR Y2 RISE B CO 8 O 9 C1 ANTICIPATOR 10 SYSTEM SWITCH X SERVICE LED (YELLOW) OFF X1 AUTO C1 1 RISE C FILTER LED (RED) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 24 VAC X2 M5902 Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications. 60-2485—8 206 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SUBBASE THERMOSTAT SYSTEM COMPONENTS L1 (HOT) R H1 ANTICIPATOR L2 2 FALL H1 3 4 SYSTEM MONITOR FAN SWITCH 1 L FAN RELAY AUTO G ON W 8 MALFUNCTION LED (RED) SYSTEM SWITCH HEAT RELAY C C1 RISE 9 C1 ANTICIPATOR HIGH SPEED LED (YELLOW) OFF LOW SPEED LED (GREEN) HEAT 10 AUTO C2 ANTICIPATOR C2 11 COMPRESSOR CONTACTOR 1 Y1 COOL COMPRESSOR CONTACTOR 2 RISE Y2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5920 Fig. 222. Schematic and hookup of T874B with Q674E. Used in standard applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 H1 ANTICIPATOR 3 4 H2 L1 (HOT) R FAN SWITCH L2 AUTO 1 ON L H2 ANTICIPATOR FAN RELAY G FALL AUX. HT. RELAY 5 W2 7 E RISE C1 AUX. HT. LED (RED) 8 SYSTEM SWITCH 9 OFF MALFUNCTION LED (RED) EM.HT. RELAY C HIGH SPEED LED (YELLOW) EM. HT. C1 ANTICIPATOR HEAT 10 C2 RISE Y1 AUTO C2 ANTICIPATOR 11 COMPRESSOR CONTACTOR 2 COOL CO Y2 RISE 1 COMPRESSOR CONTACTOR 1 LOW SPEED LED (GREEN) O POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE M5923 Fig. 223. Schematic and hookup of T874S with Q674F. Used in heat pump applications. 207 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE FALL 1 HEAT CHANGEOVER VALVE H1 B HEAT RELAY #1 H1 ANTICIPATOR W1 COMPRESSOR CONTACTOR #1 4 Y1 FAN SWITCH AUTO FAN RELAY G H2 ANTICIPATOR ON L1 (HOT) L2 1 RC H2 6 FALL HEAT RELAY #2 W2 8 SYSTEM SWITCH RH OFF C1 SERVICE LED (RED) RISE 9 HEAT L1 (HOT) L2 1 SYSTEM MONITOR A AUTO 10 COOL COMPRESSOR CONTACTOR #2 Y2 11 C2 COOL CHANGEOVER VALVE RISE O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 224. Schematic and hookup of T874A,D with Q674E. Used in standard applications. 60-2485—8 208 M5927 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE HEAT RELAY #1 FALL 1 W1 HEAT RELAY #2 H1 W2 FAN SWITCH H1 ANTICIPATOR HEAT DAMPER B AUTO 4 ON L1 (HOT) RH L2 H2 ANTICIPATOR 6 1 L2 1 L1 (HOT) RC H2 COOL DAMPER FALL O 8 SYSTEM SWITCH FAN RELAY G C1 RISE 9 COMPRESSOR CONTACTOR #2 OFF Y2 AUTO 10 COMPRESSOR CONTACTOR #1 11 Y1 C2 1 SERVICE LED (RED) RISE SYSTEM MONTIOR A POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5928 Fig. 225. Schematic and hookup of T874D with Q674C. Used in standard applications. 209 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE SYSTEM MONITOR A2 FALL SERVICE LED (RED) H1 NO FAN SWITCH H1 ANTICIPATOR HEAT RELAY #1 W1 1 SERVICE LED (RED) SYSTEM MONITOR A1 HEAT RELAY #2 4 W2 T RELAY 5 T 6 H2 L1 (HOT) 1 L2 RC H2 FALL ANTICIPATOR SYSTEM SWITCH FAN RELAY B B 7 OFF 8 L2 L1 1 (HOT) AUTO RH C1 RISE FAN RELAY O 9 O COMPRESSOR CONTACTOR #2 10 Y2 11 COMPRESSOR CONTACTOR #1 C2 RISE 1 12 Y1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 226. Schematic and hookup of T874G with Q674G. Used in standard applications. 60-2485—8 210 M5930 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE 1 CO (HEAT) FAN SWITCH W3 RELAY W3 AUTO 2 FALL SYSTEM COMPONENTS H1 ANTICIPATOR FAN RELAY G ON 3 R AUX. HT. RELAY 4 FALL 1 L2 L1 (HOT) W2 H2 EM. HT. RELAY 5 E H2 ANTICIPATOR AUX. HT. LED (GREEN) H1 FALL 6 CO (COOL) SYSTEM SWITCH 8 OFF 9 EM. HT. RISE COMPRESSOR FAULT X1 CHECK LED (RED) X2 HEAT EM. HT. LED (RED) AUTO 10 C1 ANTICIPATOR X COOL COOL CHANGEOVER RELAY O C1 RISE B 11 W1 RELAY HEAT CHANGEOVER RELAY W1 2 COMPRESSOR CONTACTOR Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 W1 - Y1 JUMPER IS Y TERMINAL; REMOVE JUMPER WHEN W1 RELAY IS USED. M1230B Fig. 227. Schematic and hookup of T874G with Q674F. Used in heat pump applications. 211 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 (HOT) 1 R 1 H1 FAN SWITCH C1 FALL Y1 2 COMP. RELAY AUTO O.L. IN. STAT. HI. PRO. G H1/C1 ANTICIPATOR ON 3 FAN RELAY L SENSOR LED (RED) 4 H2 ANTICIPATOR SERVICE 2 5 EM. HT. H2 EM. HT. RELAY O.D.S. W1 FALL SYSTEM SWITCH 6 EM. HT. E AUX. HT. LED (GREEN) ELECTRIC HEAT RELAY ELECTRIC HEAT RELAY EM. HT. LED (YELLOW) C HEAT C815A OUTDOOR THERMISTOR OFF COOL T 11 RESET O 12 COOL CHANGEOVER VALVE 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVABLE JUMPER (INSTALLED). M3259 Fig. 228. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 60-2485—8 212 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 (HOT) L2 R 1 FAN SWITCH H1 ANTICIPATOR 2 COMP. RELAY IN. STAT. O.L. 1 HI. PRO Y1 AUTO H2 ANTICIPATOR ON 3 G FAN RELAY H1 SERVICE LED (RED) 4 FALL L SERVICE 5 FALL H2 O.D.S. 2 6 SYSTEM SWITCH OFF 8 RISE EM. HT. RELAY W1 RESET CO AUX. HT. LED (GREEN) EM. HT. 9 C1 ANTICIPATOR ELECTRIC HT. RELAY EM. HT. E EM. HT. LED (YELLOW) ELECTRIC HT. RELAY HEAT C 10 COOL RISE C815A OUTDOOR THERMISTOR T AUTO C1 11 O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 REMOVABLE JUMPER (INSTALLED). COOL CHANGEOVER VALVE M3264 Fig. 229. Schematic and hookup of T874G with Q674F. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS W3 RELAY W3 O COOL CHANGEOVER VALVE H1 ANTICIPATOR L CHECK LED (RED) 1 C ANTICIPATOR COMPRESSOR MONITOR FAN RELAY FAN SWITCH 2 G AUTO ON 1 R L1 (HOT) L2 H1 C W2 FALL 3 SYSTEM SWITCH EM. HT. LED (RED) EM .HT. AUX. HT. LED (GREEN) 4 AUX. HT. RELAY E 5 H2 ANTICIPATOR H2 HEAT EM. HT. RELAY X OFF 6 B COOL FALL HEAT CHANGEOVER VALVE Y 11 1 COMPRESSOR RELAY POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5068 Fig. 230. Schematic and hookup of T874R with Q674L. Used in heat pump applications. 213 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 O H1 ANTICIPATOR FALL 3 COOL CHANGEOVER VALVE L FAN SWITCH COMPRESSOR FAULT EM. HT. LED (RED) AUTO 4 ON 1 H2 ANTICIPATOR SYSTEM SWITCH 8 E X AUX. HT. LED (GREEN) OFF EM. HT. 9 HEAT 10 2 AUTO W3 RELAY 11 W3 COMPRESSOR RELAY 12 RISE HEAT CHANGEOVER VALVE B COOL RISE CO AUX. HT. RELAY W2 C1 ANTICIPATOR H1 L2 EM. HT. RELAY FALL C1 L1 (HOT) R 5 H2 FAN RELAY G Y 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 ONLY TERMINAL B OR O TO BE USED. 0.8A MAX. M5152 Fig. 231. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT FALL SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 1 W1 H1 1 4 NO FAN SWITCH L2 RH L1 (HOT) 5 FALL H2 ANTICIPATOR HEAT RELAY 2 6 H2 W2 T 7 8 RISE C1 9 SYSTEM SWITCH OFF AUTO O C1 ANTICIPATOR RISE C2 C2 ANTICIPATOR FAN RELAY B 10 RC 11 Y2 L2 L1 (HOT) 1 COMPRESSOR CONTACTOR 2 12 Y1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR 1 M3957 Fig. 232. Schematic and hookup of T874D with Q674G. Used in standard applications. 60-2485—8 214 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT FALL H1 SUBBASE H1 ANTICIPATOR SYSTEM COMPONENTS 1 COMPRESSOR HIGH SPEED Y1 H2 ANTICIPATOR 2 3 FALL AUTO FAN G 4 ON H3 H3 ANTICIPATOR AUX. HT. W2 R 5 FAN SWITCH FALL 6 H2 EM. HT. RISE C1 W89 HEAT PUMP CONTROL PANEL B EM. HT. C1 ANTICIPATOR RISE C2 E SYSTEM SWITCH 8 C2 ANTICIPATOR 9 HEAT EM. HT. LED (YELLOW) EM. HT. LIGHT X OFF 10 SERVICE LED (RED) COOL L 11 O Y RESET T 12 SERVICE LIGHT COOL CHANGEOVER COMPRESSOR LOW SPEED OUTDOOR RESET M3952 Fig. 233. Schematic and hookup of T874W with Q674L. Used in heat pump applications. THERMOSTAT FALL SUBBASE SYSTEM COMPONENTS COMPRESSOR CONTACTOR H1 ANTICIPATOR 1 H1 2 Y1 FAN SWITCH FAN RELAY AUTO G 4 FALL R 8 RISE CO SYSTEM SWITCH 1 W1 AUX. HT. RELAY C 9 HEAT AUX. HEAT LED (RED) OFF 10 1 L1 (HOT) 6 H2 RISE C1 L2 ON H2 ANTICIPATOR C1 ANTICIPATOR COOL COOL CHANGEOVER VALVE O POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M3961 Fig. 234. Schematic and hookup of T874G with Q674B. Used in heat pump applications. 215 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR R 2 RTD1 L1 (HOT) OTD1 FAN SWITCH L2 1 3 FALL H1 W2 ON 4 ODT2 H2 ANTICIPATOR EHR2 AUX. HT. LED (GRN) 5 SYSTEM SWITCH H2 FALL EM. HT. LED (RED) OFF RTD3 RTD1 X SYSTEM MONITOR 8 COOL FAN RELAY L 9 RISE RTD2 EHR1 AUTO AUTO G HEAT C1 ANTICIPATOR CHANGEOVER RD COOL CHANGEOVER VALVE EM. HT. 10 O RISE EM. HT. RELAY C1 E LACO COMPRESSOR CONTACTOR CHP Y 1 M7064 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 235. Schematic and hookup of T874G and Q674F. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS CONTROL MODULE H1 ANTICIPATOR 1 W1 FAN SWITCH HEAT RELAY 1 W2 AUTO FALL H1 4 FALL HEAT RELAY 2 HEAT DAMPER ON B 1 RH 6 H2 ANTICIPATOR H2 RC 1 COOL DAMPER 8 C1 O SYSTEM SWITCH RISE 9 OFF 10 AUTO G FAN RELAY RISE Y2 11 C2 SERVICE LED (RED) Y1 COMPRESSOR RELAY 2 COMPRESSOR RELAY 1 A 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7570 Fig. 236. Schematic and hookup of T874A-D with Q674C. Used in standard applications. 60-2485—8 216 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT H1 ANTICIPATOR L1 (HOT) L2 R 1 FAN SWITCH 1 AUTO 2 FAN RELAY ON FALL G 3 H2 ANTICIPATOR H1 B 4 LOW LED (YELLOW) 5 SYSTEM SWITCH H2 FALL 6 HEAT HI LED (GREEN) 8 C1 HEAT 1 W1 HEAT 2 OFF W2 RISE COOL 10 COMPRESSOR CONTACTOR C1 ANTICIPATOR Y 1 M7716 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Fig. 237. Schematic and hookup of T874C with Q674B. Used in standard applications. THERMOSTAT H1 ANTICIPATOR SUBBASE 1 X FAN SWITCH 2 FALL H1 SYSTEM COMPONENTS CHECK LED (RED) AUTO G ON FAN RELAY L1 (HOT) R 4 6 HEAT PUMP RELAY H2 ANTICIPATOR SYSTEM SWITCH W1 AUX. HT. RELAY AUX. HT. FALL H2 W2 HT. PUMP 8 AUX. HT. LED (RED) 2 STAGE HT. C OFF C1 RISE 2 COOL C1 ANTICIPATOR COOL CHANGEOVER VALVE O 10 1 L2 1 B RELAY B Y1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COMPRESSOR CONTACTOR M7719 2 FACTORY INSTALLED JUMPER BETWEEN TERMINALS W1 AND Y1. Fig. 238. Schematic and hookup of T874C with Q674F. Used in heat pump applications. 217 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 G FAN RELAY H1 ANTICIPATOR W FAN SWITCH 2 AUX. HT. LED (GREEN) AUTO H1 ON EM. HT. LED (RED) FALL C1 H2 2 B COMPRESSOR MONITOR 3 F 4 R FALL 5 SYSTEM SWITCH 6 EM. HT. AUX. HT. RELAY U L1 (HOT) OUTDOOR SENSOR L2 1 T HEAT X2 OFF COOL 11 O RESET 1 COOL CHANGEOVER OUTDOOR VALVE THERMOSTAT COMPRESSOR CONTACTOR POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y M7744 2 FIELD REMOVABLE JUMPER. Fig. 239. Schematic and hookup of T874R with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS W1 1 H1 ANTICIPATOR SYSTEM OFF HEAT RELAY 2 ON B 4 B RELAY R 8 L1 (HOT) L2 FAN L1 L2 H1 FALL K1 1 K1 LO MED C1 RISE 9 G1 K2 K2 K2 K1 RELAY HI HI C1 ANTICIPATOR G2 10 MED LO K2 RELAY 3 SPEED FAN SCHEMATIC 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y1 COMPRESSOR CONTACTOR 2 FAN CONTINUOUS IN ON POSITION. Fig. 240. Schematic and hookup of T874A with Q674W. Used in standard applications. 60-2485—8 218 M7745 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 ANTICIPATOR L2 FAN SWITCH 3 H1 L1 (HOT) R AUTO 4 FALL 1 Y ON FAN RELAY COMPRESSOR CONTACTOR G H2 ANTICIPATOR 5 W2 6 H2 HEAT CHANGEOVER VALVE NO. 1 SUPL. HEAT LED (RED) L C FALL 8 SYSTEM SWITCH C1 ANTICIPATOR SUPL. HT. 9 CO E HEAT HEAT CHANGEOVER VALVE NO. 2 10 RISE HEAT HEAT CHANGEOVER CHANGEOVER VALVE NO. 2 VALVE NO. 1 O.D.T. OFF 11 COOL HEAT CHANGEOVER VALVE NO. 3 X C1 CO P X RELAY RISE 12 P RELAY O 1 COOL CHANGEOVER VALVE POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7742 Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS B H1 ANTICIPATOR 1 HEAT DAMPER FAN SWITCH W1 HEAT RELAY 1 AUTO H1 FALL G ON HEAT RELAY 2 4 FAN RELAY W2 L1 (HOT) 6 R SYSTEM SWITCH H2 ANTICIPATOR H2 FALL L2 1 OFF 8 S1 AUTO 2 C0 CHANGEOVER VALVE O OVERRIDE RISE OVERRIDE CIRCUIT S2 9 OVERRIDE CIRCUIT C1 ANTICIPATOR Y SERVICE LED (RED) 10 COMPRESSOR RELAY RISE X C1 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. ON LED (YEL) A 2 OVERRIDE IS MOMENTARY POSITION. SPRING RETURN TO (OFF) UPON SWITCH RELEASE. M7212 C Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications. 219 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FALL H1 ANTICIPATOR O FAN SWITCH COOL CHANGEOVER VALVE AUTO 2 G ON FAN RELAY H1 B B RELAY 4 L1 (HOT) R 6 SYSTEM SWITCH H2 ANTICIPATOR L2 E OFF EM. HT. H2 FALL 1 EM. HT. RELAY L EM. HT. LED (RED) HEAT AUTO RISE 8 C1 2 X COOL AUX. HEAT LED (GREEN) AUX. HEAT RELAY 9 W2 C1 ANTICIPATOR Y 10 11 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 12 2 TERMINAL LABELED C/X ON SOME MODELS. RISE CO COMPRESSOR CONTACTOR M7715 Fig. 243. Schematic and hookup of T874G with Q674F. Used in heat pump applications. THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 H1 ANTICIPATOR L2 3 H1 L1 (HOT) R FAN SWITCH AUTO 4 FALL 1 Y ON COMPRESSOR CONTACTOR G FAN RELAY H2 ANTICIPATOR 5 W2 6 H2 HEAT CHANGEOVER VALVE NO. 1 SUPL. HEAT LED (RED) L C FALL 8 C1 ANTICIPATOR CO SYSTEM SWITCH E SUPL. HT. 10 RISE HEAT HEAT CHANGEOVER CHANGEOVER VALVE NO. 2 VALVE NO. 1 O.D.T. 9 ON 11 OFF HEAT CHANGEOVER VALVE NO. 2 HEAT CHANGEOVER VALVE NO. 3 X C1 CO P X RELAY RISE 12 P RELAY O 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE Fig. 244. Schematic and hookup of T874J with Q674J. Used in heat pump applications. 60-2485—8 220 M7743 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1/C1 ANTICIPATOR SUBBASE 2 SYSTEM COMPONENTS O FAN SWITCH COOL CHANGEOVER VALVE AUTO 3 G H1 ON FAN RELAY C1 FALL B B RELAY L1 (HOT) R 4 6 H2 ANTICIPATOR L2 SYSTEM SWITCH E EM. HT. L HEAT EM. HT. LED (RED) OFF FALL 1 EM. HT. RELAY 2 H2 X COOL AUX. HT. LED (GREEN) AUX. HT. RELAY 1 W2 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. Y COMPRESSOR CONTACTOR 2 TERMINAL LABELED C/X ON SOME MODELS. M7718 Fig. 245. Schematic and hookup of T874R with Q674L. Used in heat pump applications. SUBBASE THERMOSTAT SYSTEM COMPONENTS H1 ANTICIPATOR 1 H1 NO FAN SWITCH W1 HEAT RELAY 1 W2 FALL 4 HEAT RELAY 2 L2 6 SYSTEM SWITCH H2 ANTICIPATOR H2 1 L1 (HOT) OFF FALL 8 C1 RH AUTO L1 (HOT) RC RISE L2 9 1 1 10 Y1 11 Y2 COOL CHANGEOVER VALVE POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M7717 Fig. 246. Schematic and hookup of T874C with Q674G. Used in standard applications. 221 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 FALL H1 ANTICIPATOR T H1 2 C815A OUTDOOR THERMISTOR H2 W3 H2 ANTICIPATOR FALL AUX. HT. RELAY 3 AUX. HEAT LED (GREEN) FAN SWITCH AUTO H3 ANTICIPATOR 4 G ON FAN RELAY H3 L1 (HOT) L2 1 R FALL 5 EM. HEAT LED (RED) E 6 EM. HT. RELAY RESET X1 CHECK LED (YELLOW) C CHANGEOVER RELAY (HEAT) RISE 8 C1 SYSTEM SWITCH CHANGEOVER RELAY (COOL) EM.HT. 9 HEAT C1 ANTICIPATOR 2 B O OFF 10 X2 COOL COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR RISE C2 11 Y1 12 Y2 COMPRESSOR CONTACTOR 2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING. Fig. 247. Schematic and hookup of T874W with Q674L. Used in heat pump applications. 60-2485—8 222 M6999 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 FALL H1 H1 ANTICIPATOR 3 4 H2 L1 (HOT) R FAN SWITCH L2 AUTO 1 ON L H2 ANTICIPATOR FAN RELAY G FALL AUX. HT. RELAY 5 W2 7 E RISE C1 AUX. HT. LED (RED) 8 SYSTEM SWITCH 9 OFF MALFUNCTION LED (RED) EM.HT. RELAY C HIGH SPEED LED (YELLOW) EM. HT. C1 ANTICIPATOR HEAT 10 C2 RISE Y1 AUTO C2 ANTICIPATOR 11 COMPRESSOR CONTACTOR 2 COOL CO Y2 RISE 1 COMPRESSOR CONTACTOR 1 LOW SPEED LED (GREEN) O POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. COOL CHANGEOVER VALVE M5923 Fig. 248. Schematic and hookup of T874Y with Q674F. Used in heat pump applications. 223 60-2485—8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 FALL W1 H1 1 H1 ANTICIPATOR FAN SWITCH FAN RELAY G AUTO 3 ON RC 2 HEAT RELAY 2 4 W2 6 HEAT DAMPER FALL B H2 ANTICIPATOR H2 SERVICE LED (RED) C X 8 L1 (HOT) 1 L2 SYSTEM SWITCH RH C1 HEAT RISE 9 OFF COOL DAMPER O COOL C1 ANTICIPATOR 10 COMPRESSOR CONTACTOR 1 Y1 C2 ANTICIPATOR RISE COMPRESSOR CONTACTOR 2 11 Y2 C2 1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. 2 FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER. M18622 Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications. Home and Building Control Home and Building Control Honeywell 1985 Douglas Drive North Golden Valley, MN 55422 60-2485—8 Honeywell Limited-Honeywell Limitée 35 Dynamic Drive Scarborough, Ontario M1V 4Z9 J.H. Rev. 3-01 Printed in U.S.A. on recycled paper containing at least 10% post-consumer paper fibers. www.honeywell.com
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File Type : PDF File Type Extension : pdf MIME Type : application/pdf PDF Version : 1.4 Linearized : Yes Encryption : Standard V4.4 (128-bit) User Access : Print, Copy, Extract, Assemble, Print high-res Page Mode : UseOutlines XMP Toolkit : Adobe XMP Core 4.0-c316 44.253921, Sun Oct 01 2006 17:14:39 Producer : Acrobat Distiller 5.0.5 (Windows) Create Date : 1999:07:07 12:30:47Z Modify Date : 2007:05:07 13:49:26-05:00 Metadata Date : 2007:05:07 13:49:26-05:00 Creator Tool : FrameMaker 6.0 Format : application/pdf Creator : HBC Technical Communications Description : Product Data Title : 60-2485 - T874 Multistage Thermostats and Q674 Subbases Document ID : uuid:6deddc7f-9331-446d-b4e8-cfa56460dd07 Instance ID : uuid:18a758e3-2435-445e-ad5b-dcb7c0c27f76 Page Count : 224 Subject : Product Data Author : HBC Technical CommunicationsEXIF Metadata provided by EXIF.tools