Carrier 48Vtn Users Manual 48VT 05SI

48VT(N) 48VT-05SI

48VT(N) to the manual d54aa3ff-51b5-4b7c-880c-3404ca198c64

2015-01-24

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48VT(N) ---A
Performancet 14 SEER Single ---Packaged HYBRID HEAT®
Dual Fuel System with Puronr (R ---410A) Refrigerant
Single And Three Phase
2---5 Nominal Tons (Sizes 24---60)

Installation Instructions
NOTE: Read the entire instruction manual before starting the
installation.
NOTE: Installer: Make sure the Owner’s Manual and Service
Instructions are left with the unit after installation.

TABLE OF CONTENTS
PAGE
SAFETY CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 1
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
RECEIVING AND INSTALLATION . . . . . . . . . . . . . . . . . 2--13
Check Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Identify Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Inspect Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Provide Unit Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Roof Curb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Slab Mount . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Field Fabricate Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Provide Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Rig and Place Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Connect Condensate Drain . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Install Flue Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Install Gas Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Install Duct Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Configuring Units for Downflow (Vertical)
Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Install Electrical Connections . . . . . . . . . . . . . . . . . . . . . . . . 11
High--Voltage Connections . . . . . . . . . . . . . . . . . . . . . . . . 11
Special Procedures for 208--V Operation . . . . . . . . . . . . . . 11
Control Voltage Connections . . . . . . . . . . . . . . . . . . . . . . . 11
Balance Point Setting Thermidistat or Hybrid Heat
Thermostat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Transformer Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
PRE--START--UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
START--UP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13--17
Check for Refrigerant Leaks . . . . . . . . . . . . . . . . . . . . . . . . . 13
Unit Sequence of Operation . . . . . . . . . . . . . . . . . . . . . . . . . 13
Start--Up Heating and Make Adjustments . . . . . . . . . . . . . . . 13
Checking Heating Control . . . . . . . . . . . . . . . . . . . . . . . . . 14
Check Gas Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Adjust Gas Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Check Burner Flame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Start--Up Cooling and Make Adjustments . . . . . . . . . . . . . . . 16
Checking Cooling Control Operation . . . . . . . . . . . . . . . . 16
Checking and Adjusting Refrigerant . . . . . . . . . . . . . . . . . 16
Indoor Airflow and Airflow Adjustments . . . . . . . . . . . . . 16
Continuous Fan Operation . . . . . . . . . . . . . . . . . . . . . . . . 17
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27--33
Air Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Indoor Blower and Motor . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Flue Gas Passageways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Limit Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Burner Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Main Burners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Outdoor Coil, Indoor Coil, & Condensate Drain Pan . . . . . . 28

A09042

Fig. 1 -- Unit 48VT--A
Outdoor Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Controls and Wiring . . . . . . . . . . . . . . . . . . . . . . .
Refrigerant Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Indoor Airflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Check Defrost Thermostat . . . . . . . . . . . . . . . . . . . . . . . . . . .
PuronR Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
START--UP CHECKLIST . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29
29
29
30
30
30
30
33
33

SAFETY CONSIDERATIONS
Improper installation, adjustment, alteration, service maintenance,
or use can cause explosion, fire, electrical shock, or other
conditions which may cause death, personal injury, or property
damage. Consult a qualified installer, service agency, or your
distributor or branch for information or assistance. The qualified
installer or agency must use factory--authorized kits or accessories
when modifying this product. Refer to the individual instructions
packaged with the kits or accessories when installing.
Follow all safety codes. Wear safety glasses, protective clothing,
and work gloves. Have a fire extinguisher available. Read these
instructions thoroughly and follow all warnings or cautions
included in literature and attached to the unit. consult local
building codes, the current editions of the National Fuel Gas Code
(NFGC) NFPA 54/ANSI Z223.1, and the National Electrical Code
(NEC) NFPA 70.
In Canada refer to the current editions of the National Standards of
Canada CAN/CSA--B149.1 and .2 Natural Gas and Propane
Installation codes, and Canadian Electrical Code CSA C22.1
.
Recognize safety information. This is the safety--alert symbol
When you see this symbol on the unit and in instructions or manuals, be alert to the potential for personal injury. Understand these
1

signal words: DANGER, WARNING, and CAUTION. These
words are used with the safety--alert symbol. DANGER identifies
the most serious hazards which will result in severe personal injury
or death. WARNING signifies hazards which could result in personal injury or death. CAUTION is used to identify unsafe practices which may result in minor personal injury or product and property damage. NOTE is used to highlight suggestions which will
result in enhanced installation, reliability, or operation.

WARNING

ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.

48VT-- A

Before installing or servicing system, always turn off main
power to system. There may be more than one disconnect
switch. Turn off accessory heater power switch if
applicable. TAG THE DISCONNECT SWITCH WITH A
SUITABLE WARNING LABEL.

WARNING

FIRE, EXPLOSION, ELECTRICAL SHOCK AND
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal
injury, death or property damage.
A qualified installer or agency must use only
factory--authorized kits or accessories when modifying this
product.

CAUTION

CUT HAZARD
Failure to follow this caution may result in personal injury.
When removing access panels (see Fig. 19) or performing
maintenance functions inside your unit, be aware of sharp
sheet metal parts and screws. Although special care is taken
to reduce sharp edges to a minimum, be extremely careful
when handling parts or reaching into the unit.

INTRODUCTION
The 48VT--A unit (see Fig. 1) is a fully self--contained,
combination Category I gas heating/electric heating and cooling
unit designed for outdoor installation (See Fig. 2 and 3 for unit
dimensions). All unit sizes have return and discharge openings for
both horizontal and downflow configurations, and are factory
shipped with all downflow duct openings covered. Units may be
installed either on a rooftop, a cement slab, or directly on the
ground, if local codes permit (See Fig. 4 for roof curb dimensions).
Models with an N in the fifth position of the model number are
dedicated Low NOx units designed for California installations.
These models meet the California maximum oxides of nitrogen
(NOx) emissions requirements of 40 nanograms/joule or less as
shipped from the factory and must be installed in California Air
Quality Management Districts or any other regions in North
America where a Low NOx rule exists.

RECEIVING AND INSTALLATION
Step 1 — Check Equipment
IDENTIFY UNIT
The unit model number and serial number are stamped on the unit
information plate. Check this information against shipping papers.

INSPECT SHIPMENT
Inspect for shipping damage before removing packaging materials.
If unit appears to be damaged or is torn loose from its anchorage,
have it examined by transportation inspectors before removal.
Forward claim papers directly to transportation company.
Manufacturer is not responsible for any damage incurred in transit.
Check all items against shipping list. Immediately notify the
nearest equipment distribution office if any item is missing. To
prevent loss or damage, leave all parts in original packages until
installation.

Step 2 — Provide Unit Support
For hurricane tie downs, contact distributor for details and PE
(Professional Engineering) Certificate if required.
ROOF CURB
Install accessory roof curb in accordance with instructions shipped
with curb (See Fig. 4). Install insulation, cant strips, roofing, and
flashing. Ductwork must be attached to curb.
IMPORTANT: The gasketing of the unit to the roof curb is
critical for a water tight seal. Install gasketing material supplied
with the roof curb. Improperly applied gasketing also can result in
air leaks and poor unit performance.
Curb should be level to within 1/4 in. (6 mm). This is necessary for
unit drain to function properly. Refer to accessory roof curb
installation instructions for additional information as required.
SLAB MOUNT
Place the unit on a solid, level concrete pad that is a minimum of 4
in. (102 mm) thick with 2 in. (51 mm) above grade. The slab
should be flush on the compressor end of the unit (to allow
condensate drain installation) and should extend 2 in. (51 mm) on
the three remaining sides of the unit. Do not secure the unit to the
slab except when required by local codes.

Step 3 — Field Fabricate Ductwork
Secure all ducts to roof curb and building structure on vertical
discharge units. Do not connect ductwork to unit. For horizontal
applications, unit is provided with flanges on the horizontal
openings. All ductwork should be secured to the flanges. Insulate
and weatherproof all external ductwork, joints, and roof openings
with counter flashing and mastic in accordance with applicable
codes.
Ducts passing through an unconditioned space must be insulated
and covered with a vapor barrier.
If a plenum return is used on a vertical unit, the return should be
ducted through the roof deck to comply with applicable fire codes.
Read unit rating plate for any required clearances around ductwork.
Cabinet return--air static shall not exceed --.25 IN. W.C.

Step 4 — Provide Clearances
The required minimum operating and service clearances are shown
in Fig. 2 and 3.
IMPORTANT: Do not restrict outdoor airflow. An air restriction
at either the outdoor--air inlet or the fan discharge may be
detrimental to compressor life.
The condenser fan pulls air through the condenser coil and
discharges it through the top grille. Be sure that the fan discharge
does not recirculate to the condenser coil. Do not locate the unit in
either a corner or under an overhead obstruction. The minimum
clearance under a partial overhang (such as a normal house
overhang) is 48--in. (1219 mm) above the unit top. The maximum
horizontal extension of a partial overhang must not exceed 48--in.
(1219 mm).
Do not place the unit where water, ice, or snow from an overhang
or roof will damage or flood the unit. Do not install the unit on
carpeting or other combustible materials. The unit may be installed
on wood flooring or on Class A, B, or C roof covering materials.

48VT-- A
A09146

Fig. 2 -- 48VT--A24--30 Unit Dimensions

48VT-- A

A09147

Fig. 3 -- 48VT--A36--60 Unit Dimensions

HVAC unit
base rails

HVAC unit
basepan

Sealing
Gasket

Roofcurb

Anchor screw

Wood nailer*

Flashing field
supplied

Roofcurb*
Insulation
(field supplied)

Cant strip
field supplied

SMALL CURB

A09110

*Provided with roofcurb

A09090

ROOF CURB DETAIL

B
C

A
E
D

LARGE CURB

A09095
A09111

UNIT SIZE
Small
Large

CATALOG
NUMBER
CPRFCURB010A00
CPRFCURB011A00
CPRFCURB012A00
CPRFCURB013A00

A
IN. (mm)
11 (279)
14 (356)
11 (279)
14 (356)

B
IN. (mm)*

C
IN. (mm)

D
IN. (mm)

16 (406)

47.8 (1214)

10 (254)

E
IN. (mm)

F
IN. (mm)

32.4 (822)

14 (356)

2.7 (69)
43.9 (1116)

NOTES:
1. Roof curb must be set up for unit being installed.
2. Seal strip must be applied, as required, to unit being installed.
3. Roof curb is made of 16--gauge steel.
4. Attach ductwork to curb (flanges of duct rest on curb).
5. Insulated panels: 1--in. (25.4 mm) thick fiberglass 1 lb. density.

literature dimensional drawing to ensure that “Y” is greater than 14
IMPORTANT: Do not install large base pan HYBRID HEAT
in. (356 mm). Do not install any large base pan unit onto the
units onto the small base pan (common curb). The center of gravity
common curb with a “Y” dimension (center of gravity) less than 14
on a large base pan HYBRID HEAT unit could overhang the curb
in. (356 mm).
causing an unsafe condition. Before installing any large base pan
unit onto the common curb, check the “Y” distance in the product
Fig. 4 -- Roof Curb Dimensions

48VT-- A

Roofing material
field supplied

CAUTION - NOTICE TO RIGGERS
PRUDENCE - AVIS AUX MANIPULATEUR
ACCESS PANELS MUST BE IN PLACE WHEN RIGGING.
PANNEAUX D'ACCES DOIT ÊTRE EN PLACE POUR MANIPULATION.

Use top skid as spreader bar. / Utiliser la palette du haut comme barre de répartition
DUCTS

MINIMUM HEIGHT: 36" (914.4 mm)
HAUTEUR MINIMUM

SEAL STRIP MUST BE IN
PLACE BEFORE PLACING
UNIT ON ROOF CURB

BANDE SCELLANT DOIT ÊTRE
EN PLACE AVANT DE PLACER
L'UNITÉ SUR LA BASE DE TOIT

48VT-- A

UNIT HEIGHT
HAUTEUR D'UNITÉ

DETAIL A
VOIR DÉTAIL A

SEE DETAIL A
VOIR DÉTAIL A

50CY502286 2.0

A09051

Unit

Rigging
Weight

368

30
kg
167

lb
378

kg
171

Unit
Rigging
Weight

450

204

491

223

513

233

543

246

NOTE: See dimensional drawing for corner weight distribution.

Fig. 5 -- 48VT--A Suggested Rigging

Step 5 — Rig and Place Unit

WARNING

PERSONAL INJURY OR PROPERTY DAMAGE
HAZARD
Failure to follow this warning could result in personal
injury, death or property damage.

Inspection
Prior to initial use, and at monthly intervals, all rigging shackles,
clevis pins, and straps should be visually inspected for any
damage, evidence of wear, structural deformation, or cracks.
Particular attention should be paid to excessive wear at hoist
hooking points and load support areas. Materials showing any kind
of wear in these areas must not be used and should be discarded.

When installing the unit on a rooftop, be sure the roof will
support the additional weight.
Rigging and handling of this equipment can be hazardous for
many reasons due to the installation location (roofs, elevated
structures, etc.).
Only trained, qualified crane operators and ground support staff
should handle and install this equipment.
When working with this equipment, observe precautions in the
literature, on tags, stickers, and labels attached to the equipment,
and any other safety precautions that might apply.
Training for operators of the lifting equipment should include, but
not be limited to, the following:
1. Application of the lifter to the load, and adjustment of the
lifts to adapt to various sizes or kinds of loads.
2. Instruction in any special operation or precaution.
3. Condition of the load as it relates to operation of the lifting
kit, such as balance, temperature, etc.
Follow all applicable safety codes. Wear safety shoes and work
gloves.

WARNING

UNIT FALLING HAZARD
Failure to follow this warning could result in personal
injury or death.
Never stand beneath rigged units or lift over people.

WARNING

PROPERTY DAMAGE HAZARD
Failure to follow this warning could result in personal
injury/death or property damage.
When straps are taut, the clevis should be a minimum of 36
in. (914 mm) above the unit top cover.

Rigging/Lifting of Unit (See Fig. 5)
Lifting holes are provided in base rails as shown in Fig. 2 and 3.
1. Leave top shipping skid on the unit for use as a spreader bar
to prevent the rigging straps from damaging the unit. If the
skid is not available, use a spreader bar of sufficient length
to protect the unit from damage.
2. Attach shackles, clevis pins, and straps to the base rails of
the unit. Be sure materials are rated to hold the weight of the
unit (See Fig. 5).
6

Step 6 — Connect Condensate Drain
NOTE: When installing condensate drain connection be sure to
comply with local codes and restrictions.
Model 48VT--A disposes of condensate water through a 3/4 in.
NPT fitting which exits through the compressor access panel (See
Fig. 2 and 3 for location).
Condensate water can be drained directly onto the roof in rooftop
installations (where permitted) or onto a gravel apron in ground
level installations. Install a field--supplied condensate trap at end
of condensate connection to ensure proper drainage. Make sure that
the outlet of the trap is at least 1 in. (25 mm) lower than the
drain--pan condensate connection to prevent the pan from
overflowing (See Fig. 6). Prime the trap with water. When using a
gravel apron, make sure it slopes away from the unit.
If the installation requires draining the condensate water away
from the unit, install a 2--in. (51 mm) trap at the condensate
connection to ensure proper drainage (See Fig. 6). Make sure that
the outlet of the trap is at least 1 in. (25 mm) lower than the
drain--pan condensate connection. This prevents the pan from
overflowing.
Prime the trap with water. Connect a drain tube -- using a minimum
of 3/4--in. PVC or 3/4--in. copper pipe (all field--supplied) -- at the
outlet end of the 2--in. (51 mm) trap. Do not undersize the tube.
Pitch the drain tube downward at a slope of at least 1--in. (25 mm)
for every 10 ft (3 m) of horizontal run. Be sure to check the drain
tube for leaks.
TRAP
OUTLET
1-in. (25 mm) min.

2-in. (51 mm) min.

A09052

Fig. 6 -- Condensate Trap

Step 7 — Install Flue Hood

The flue assembly is secured and shipped in the return air duct.
Remove duct cover to locate the assembly (See Fig. 8).
NOTE:
Dedicated low NOx models MUST be installed in
California Air Quality Management Districts where a Low NOx
rule exists.
These models meet the California maximum oxides of nitrogen
(NOx) emissions requirements of 40 nanograms/joule or less as
shipped from the factory.
NOTE: Low NOx requirements apply only to natural gas
installations.

WARNING

CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal
injury or death.
The venting system is designed to ensure proper venting.
The flue hood assembly must be installed as indicted in this
section of the unit installation instructions.

Install the flue hood as follows:
1. This installation must conform with local building codes
and with the National Fuel Gas Code (NFGC) NFPA 54 /
ANSI Z223.1, (in Canada, CAN/CGA B149.1, and
B149.2) latest revision. Refer to Provincial and local
plumbing or wastewater codes and other applicable local
codes.
2. Remove flue hood from shipping location (inside the return
section of the blower compartment--see Fig. 8). Remove the
return duct cover to locate the flue hood. Place flue hood
assembly over flue panel. Orient screw holes in flue hood
with holes in the flue panel.
3. Secure flue hood to flue panel by inserting a single screw on
the top flange and the bottom flange of the hood.

Step 8 — Install Gas Piping
The gas supply pipe enters the unit through the access hole
provided. The gas connection to the unit is made to the 1/2--in.
(12.7 mm) FPT gas inlet on the gas valve.
Install a gas supply line that runs to the heating section. Refer to
Table 2 and the NFGC for gas pipe sizing. Do not use cast--iron
pipe. It is recommended that a black iron pipe is used. Check the
local utility for recommendations concerning existing lines. Size
gas supply piping for 0.5 IN. W.C. maximum pressure drop. Never
use pipe smaller than the 1/2--in. (12.7 mm) FPT gas inlet on the
unit gas valve.
For natural gas applications, the gas pressure at unit gas connection
must not be less than 4.0 IN. W.C. or greater than 13 IN. W.C.
while the unit is operating. For propane applications, the gas
pressure must not be less than 11.0 IN. W.C. or greater than 13 IN.
W.C. at the unit connection.
A 1/8--in. (3.2 mm) NPT plugged tapping, accessible for test gauge
connection, must be installed immediately upstream of the gas
supply connection to the gas valve.
When installing the gas supply line, observe local codes pertaining
to gas pipe installations. Refer to the NFGC NFPA 54/ANSI
Z223.1 latest edition (in Canada, CAN/CGA B149.1).
NOTE: In the state of Massachusetts:
1. Gas supply connections MUST be performed by a licensed
plumber or gas fitter.
2. When flexible connectors are used, the maximum length
shall not exceed 36 in. (915 mm).
3. When lever handle type manual equipment shutoff valves
are used, they shall be T--handle valves.
4. The use of copper tubing for gas piping is NOT approved
by the state of Massachusetts.
In the absence of local building codes, adhere to the following
pertinent recommendations:
1. Avoid low spots in long runs of pipe. Grade all pipe 1/4 in.
(6.35 mm) for every 15 ft (4.6 m) of length to prevent traps.
Grade all horizontal runs downward to risers. Use risers to
connect to heating section and to meter.
2. Protect all segments of piping system against physical and
thermal damage. Support all piping with appropriate straps,
hangers, etc. Use a minimum of one hanger every 6 ft (1.8
m). For pipe sizes larger than 1/2 in., (12.7 mm) follow
recommendations of national codes.
3. Apply joint compound (pipe dope) sparingly and only to
male threads of joint when making pipe connections. Use
only pipe dope that is resistant to action of liquefied
petroleum gases as specified by local and/or national codes.
Never use Teflon tape.
4. Install sediment trap in riser leading to heating section (See
Fig. 7). This drip leg functions as a trap for dirt and
condensate.

48VT-- A

3. Attach a clevis of sufficient strength in the middle of the
straps. Adjust the clevis location to ensure unit is lifted level
with the ground.
After the unit is placed on the roof curb or mounting pad, remove
the top skid.

made specifically for the detection of leaks (or method
specified by local codes and/or regulations).

Step 9 — Install Duct Connections
The unit has duct flanges on the supply-- and return--air openings
on the side and bottom of the unit. For downshot applications, the
ductwork connects to the roof curb (See Fig. 2 and 3 for
connection sizes and locations).

Configuring Units for Downflow (Vertical) Discharge

TEE

OUT

ELECTRICAL SHOCK HAZARD
NIPPLE

Failure to follow this warning could result in personal injury
or death.

CAP

Before installing or servicing system, always turn off main
power to system. There may be more than one disconnect
switch. Tag the disconnect switch with a suitable warning
label.
1. Open all electrical disconnects before starting any service
work.
2. Remove horizontal (metal) duct covers to access vertical
(downflow) discharge duct knockouts in unit basepan. (See
Fig. 8.)
3. Starting in a corner as shown in Fig. 9, score the panel in
both directions from the corner. Tap the panel out from the
scored corner using a small hammer. Be careful and not
damage any other part of the unit.
4. If unit ductwork is to be attached to vertical opening flanges
on the unit base (jackstand applications only), do so at this
time.

48VT-- A

C99020

Fig. 7 -- Sediment Trap
5. Install an accessible, external, manual main shutoff valve in
gas supply pipe within 6 ft (1.8 m) of heating section.
6. Install ground--joint union close to heating section between
unit manual shutoff and external manual main shut--off
valve.
7. Pressure test all gas piping in accordance with local and
national plumbing and gas codes before connecting piping
to unit.
NOTE: Pressure test the gas supply system after the gas supply
piping is connected to the gas valve. The supply piping must be
disconnected from the gas valve during the testing of the piping
systems when test pressure is in excess of 0.5 psig. Pressure test the
gas supply piping system at pressures equal to or less than 0.5 psig.
The unit heating section must be isolated from the gas piping
system by closing the external main manual shutoff valve and
slightly opening the ground--joint union.

WARNING

PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in property damage.
Collect ALL screws that were removed. Do not leave screws
on rooftop as permanent damage to the roof may occur.

WARNING

FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal injury,
death and/or property damage.
--Connect gas pipe to unit using a backup wrench to avoid
damaging gas controls.
--Never purge a gas line into a combustion chamber. Never
test for gas leaks with an open flame. Use a commercially
available soap solution made specifically for the detection of
leaks to check all connections.
--Use proper length of pipe to avoid stress on gas control
manifold.
--If a flexible connector is required or allowed by authority
having jurisdiction, black iron pipe shall be installed at
furnace gas valve and extend a minimum of 2 in. (51 mm)
outside furnace casing.
--If codes allow a flexible connector, always use a new
connector. do not use a connector which has previously
serviced another gas appliance.
8. Check for gas leaks at the field--installed and
factory--installed gas lines after all piping connections have
been completed. Use a commercially available soap solution

CAUTION

5. It is recommended that the base insulation around the
perimeter of the vertical return--air opening be secured to
the base with aluminum tape. Applicable local codes may
require aluminum tape to prevent exposed fiberglass.
6. Reinstall both horizontal duct covers. Ensure opening is
air-- and watertight.
7. After completing unit conversion, perform all safety checks
and power up unit.
NOTE: The design and installation of the duct system must be in
accordance with the standards of the NFPA for installation of
nonresidence--type air conditioning and ventilating systems, NFPA
90A or residence--type, NFPA 90B; and/or local codes and
ordinances.
Adhere to the following criteria when selecting, sizing, and
installing the duct system:
1. Units are shipped for horizontal duct installation (by
removing duct covers).
2. Select and size ductwork, supply--air registers, and
return--air grilles according to American Society of Heating,
Refrigeration and Air Conditioning Engineers (ASHRAE)
recommendations.
3. Use flexible transition between rigid ductwork and unit to
prevent transmission of vibration. The transition may be
screwed or bolted to duct flanges. Use suitable gaskets to
ensure weather tight and airtight seal.

Table 1 – Physical Data -- Unit 48VT--A
UNIT SIZE
NOMINAL CAPACITY --- ton
SHIPPING WEIGHT --- lb.
(kg)
COMPRESSORS
Quantity
REFRIGERANT (R--- 410A)
Quantity --- lb
(kg)
REFRIGERANT METERING
DEVICE
OUTDOOR ORIFICE

024040
2
368
167

024060
2
368
167

030040
2--- 1/2
378
171

030060
2--- 1/2
378
171

9.5
4.3

10.5
4.8

in. (qty)
(mm)
OUTDOOR COIL
Rows...Fins/in.
Face Area--- sq ft
OUTDOOR FAN
Nominal Cfm
Diameter--- in.
(mm)
Motor Hp (Rpm)
INDOOR COIL
Rows...Fins/in.
Face Area--- sq ft
INDOOR BLOWER
Nominal Cooling Airflow--- (CFM)
Size--- in.
(mm)
Motor --- hp
FURNACE SECTION*
Burner Orifice
Natural Gas Qty...Drill Size
Propane GasQty...Drill Size
HIGH--- PRESSURE SWITCH
(psig) Cut--- out
Reset (Auto)
LOSS--- OF--- CHARGE /
LOW--- PRESSURE SWITCH
(Liquid Line) (psig)
Cut--- out
Reset (auto)
RETURN--- AIR FILTERS † }
Throwaway (in.)
(mm)

0.032 (2)
.81

0.038 (2)
.97

0.040 (2)
1.02

2...21
13.6

2...21
15.4

2...21
13.6

2...21
19.4

2500
22
559
1/8 (825)

2600
22
559
1/8 (825)

3000
22
559
1/4 (1100)

3500
22
559
1/8 (825)

3...17
3.7

3...17
4.7

800
10x10
254x254
1/2

1000
10x10
254x254
1/2

1200
11x10
279x254
3/4

1400
11x10
279x254
3/4

2...44
2...55

2...38
2...53

2...44
2...55

2...44
2...53

2...38
2...53

3...38
3...53

2...38
2...53

3...38
3...53

Scroll
1

036060
3
450
204

036090
3
450
204

042060
3--- 1/2
491
223

042090
3--- 1/2
491
223

9.0
4.1

14.0
6.4

Indoor--- TXV, Outdoor--- Accurater

650 +/--- 15
420 +/--- 25

20 +/--- 5
45 +/--- 10
20x20x1
508x508x25

20x24x1
508x610x25

24x30x1
610x762x25

*Based on altitude of 0 to 2000 ft (0 ---610 m).
{Required filter sizes shown are based on the larger of the ARI (Air Conditioning and Refrigeration Institute) rated cooling airflow or the heating airflow velocity of
300 ft/minute for high ---capacity type. Air filter pressure drop for non ---standard filters must not exceed 0.08 IN. W.C.
} If using accessory filter rack refer to filter rack installation instructions for correct filter size and quantity.

Horizontal Duct Covers
A09076

INSTRUCTIONS FOR REMOVING DOWNSHOT PANELS
1. Score groove in corner 1 in both directions as far as you can reach.
2. Starting in corner 1, tap-out all sides with a small hammer. Be careful
not to damage any other part of unit.
3. If side from corner 3 to 4 is not accessible due to heat exchanger,
pivot panel up and down by hand until remaining side breaks off.

Basepan
Downflow
(Vertical)
Supply
Knockout

A09054

Basepan
Downflow
(Vertical)
Return
Knockout

Fig. 9 -- Vertical (Downflow) Discharge Duct Knockouts

A09077

Fig. 8 -- Supply and Return Duct Opening
9

48VT-- A

0.038 (Left OD Coil)
0.040 (Right OD Coil)
.97/1.02

48VT-- A

Table 1 -- Physical Data -- Unit 48VT--A Cont’d)
UNIT SIZE
048090
048115
048130
060090
060115
060130
NOMINAL CAPACITY --- ton
4
4
4
5
5
5
SHIPPING WEIGHT--- lb
513
513
513
543
543
546
(kg)
233
233
233
246
246
246
COMPRESSORS
Scroll
Quantity
1
REFRIGERANT (R --- 410A)
17.0
17.0
17.0
16.0
16.0
16.0
Quantity --- lb
7.7
7.7
7.7
7.3
7.3
7.3
(kg )
REFRIGERANT METERING DEVICE
TXV
OUTDOOR ORIFICE --- in. (qty)
0.040 (2)
0.049 (2)
(mm)
1.02
1.24
OUTDOOR COIL
2...21
2...21
2...21
2...21
2...21
2...21
Rows...Fins --- in.
19.4
19.4
19.4
23.3
23.3
23.3
Face Area--- sq ft
OUTDOOR FAN
3500
3500
3500
3800
3800
3800
Nominal Cfm
22
22
22
22
22
22
Diameter--- in.
559
559
559
559
559
559
(mm)
1/4 (1100)
1/4 (1100)
1/4 (1100)
1/3 (1100)
1/3 (1100)
1/3 (1100)
Motor Hp --- Rpm
INDOOR COIL
3...17
3...17
3...17
4...17
4...17
4...17
Rows...Fins --- in.
5.7
5.7
5.7
5.7
5.7
5.7
Face Area--- sq ft
INDOOR BLOWER
1600
1600
1600
1750
1750
1750
Nominal Cooling Airflow--- (CFM)
11x10
11x10
11x10
11x10
11x10
11x10
Size --- in.
279x254
279x254
279x254
279x254
279x254
279x254
(mm)
1.0
1.0
1.0
1.0
1.0
1.0
Motor --- hp
FURNACE SECTION*
Burner Orifice
3...38
3...33
3...31
3...38
3...33
3...31
Natural Gas Qty...Drill Size
3...53
3...51
3...49
3...53
3...51
3...49
Propane GasQty...Drill Size
HIGH --- PRESSURE SWITCH (psig)
650 +/ ---15
Cut--- out
420 +/ ---25
Reset (Auto)
LOSS--- OF--- CHARGE /
LOW --- PRESSURE SWITCH
(Liquid Line) (psig)
20 +/ ---5
Cut--- out
45 +/ ---10
Reset (auto)
RETURN--- AIR FILTERS †
24x36x1
Throwaway (in.)
(610x914x25)
(mm)
*Based on altitude of 0 to 2000 ft (0 ---610 m).
{Required filter sizes shown are based on the larger of the ARI (Air Conditioning and Refrigeration Institute) rated cooling airflow or the heating airflow velocity of
300 ft/minute for high ---capacity type. Air filter pressure drop for non ---standard filters must not exceed 0.08 IN. W.C.
} If using accessory filter rack refer to filter rack installation instructions for correct filter size and quantity.

Table 2 – Maximum Gas Flow Capacity*

NOMINAL
LENGTH OF PIPE, FT (m)†
INTERNAL
IRON
DIAMETER
10
20
30
40
50
60
70
80
90
100
125
150
175
PIPE, SIZE
(IN.)
(3.0)
(6.1)
(9.1)
(12.2)
(15.2)
(18.3)
(21.3)
(24.4)
(27.4)
(30.5)
(31.1)
(45.7)
(53.3)
(IN.)
1/2
.622
175
120
97
82
73
66
61
57
53
50
44
40
—
3/4
.824
360
250
200
170
151
138
125
118
110
103
93
84
77
1
1.049
680
465
375
320
285
260
240
220
205
195
175
160
145
1 ---1/4
1.380
1400
950
770
600
580
530
490
460
430
400
360
325
300
1 ---1/2
1.610
2100
1460
1180
990
900
810
750
690
650
620
550
500
460
* Capacity of pipe in cu ft of gas per hr for gas pressure of 0.5 psig or less. Pressure drop of 0.5--IN. W.C. (based on a 0.60 specific gravity gas). Refer to Table 2
and the NFGC NFPA 54/ANSI.
† This length includes an ordinary number of fittings.

Table 3 – Heating Inputs
HEATING INPUT
(BTUH)

NUMBER OF
ORIFICES

40,000
60,000
90,000
115,000
130,000

2
2
3
3
3

Min
4.0
4.0
4.0
4.0
4.0

GAS SUPPLY PRESSURE (IN. W.C.)
Natural{
Propane*{
Max
Min
Max
13.0
11.0
13.0
13.0
11.0
13.0
13.0
11.0
13.0
13.0
11.0
13.0
13.0
11.0
13.0

MANIFOLD PRESSURE
(IN. W.C.)
Natural{
Propane*†
3.2∼3.8
10.0∼11.0
3.2∼3.8
10.0∼11.0
3.2∼3.8
10.0∼11.0
3.2∼3.8
10.0∼11.0
3.2∼3.8
10.0∼11.0

*When a unit is converted to propane, different size orifices must be used. See separate, natural ---to ---propane conversion kit instructions.
{Based on altitudes from sea level to 2000 ft (610 m) above sea level. In th e U.S.A. for altitudes above 2000 ft (610 m), reduce input rating 4 percent for each
additional 1000 ft (305 m) above sea level. In Canada, from 2000 ft (610 m) above sea level to 4500 ft (1372 m) above sea level, derate the unit 10 percent.

200
(61.0)
—
72
135
280
430

Step 10 — Install Electrical Connections

WARNING

ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
The unit cabinet must have an uninterrupted, unbroken
electrical ground. This ground may consist of an electrical
wire connected to the unit ground screw in the control
compartment, or conduit approved for electrical ground when
installed in accordance with NEC, NFPA 70 National Fire
Protection Association (latest edition) (in Canada, Canadian
Electrical Code CSA C22.1) and local electrical codes.

CAUTION

The unit must have a separate electrical service with a
field--supplied, waterproof disconnect switch mounted at, or within
sight from, the unit. Refer to the unit rating plate, NEC and local
codes for maximum fuse/circuit breaker size and minimum circuit
amps (ampacity) for wire sizing.
The field--supplied disconnect switch box may be mounted on the
unit over the high--voltage inlet hole when the standard power and
low--voltage entry points are used (See Fig. 2 and 3 for acceptable
location).
See unit wiring label (Fig. 15 and 16) and Fig. 10 for reference
when making high voltage connections. Proceed as follows to
complete the high--voltage connections to the unit.
Single phase units:
1. Run the high--voltage (L1, L2) and ground lead into the
control box.
2. Connect ground lead to chassis ground connection.
3. Locate the black and yellow wires connected to the line side
of the contactor.
4. Connect field L1 to black wire on connection 11 of the
compressor contactor.
5. Connect field wire L2 to yellow wire on connection 23 of
the compressor contactor.
Three--phase units:
1. Run the high--voltage (L1, L2, L3) and ground lead into the
control box.
2. Connect ground lead to chassis ground connection.
3. Locate the black and yellow wires connected to the line side
of the contactor.
4. Connect field L1 to black wire on connection 11 of the
compressor contactor.
5. Connect field wire L3 to yellow wire on connection 13 of
the compressor contactor.
6. Connect field wire L2 to blue wire from compressor.

Special Procedures for 208-- V Operation

UNIT COMPONENT DAMAGE HAZARD
Failure to follow this caution may result in damage to the unit
being installed.
1. Make all electrical connections in accordance with NEC
NFPA 70 (latest edition) and local electrical codes
governing such wiring. In Canada, all electrical
connections must be in accordance with CSA standard
C22.1 Canadian Electrical Code Part 1 and applicable
local codes. Refer to unit wiring diagram.
2. Use only copper conductor for connections between
field--supplied electrical disconnect switch and unit. DO
NOT USE ALUMINUM WIRE.
3. Be sure that high--voltage power to unit is within
operating voltage range indicated on unit rating plate. On
3--phase units, ensure phases are balanced within 2
percent. Consult local power company for correction of
improper voltage and/or phase imbalance.
4. Insulate low--voltage wires for highest voltage contained
within conduit when low--voltage control wires are in
same conduit as high--voltage wires.
5. Do not damage internal components when drilling
through any panel to mount electrical hardware, conduit,
etc.

High-- Voltage Connections
When routing power leads into unit, use only copper wire between
disconnect and unit. The high voltage leads should be in a conduit
until they enter the duct panel; conduit termination at the duct
panel must be watertight.

WARNING

ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Make sure the power supply to the unit is switched OFF before
making any wiring changes. Tag the disconnect switch with a
suitable warning label. With disconnect switch open, move
black wire from transformer (3/16 in.) terminal marked 230 to
terminal marked 200. This retaps transformer to primary
voltage of 208 vac.

WARNING

ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Before making any wiring changes, make sure the gas supply
is switched off first. Then switch off the power supply to the
unit and install lockout tag.

Control Voltage Connections
Do not use any type of power--stealing thermostat. Unit control
problems may result.
Use no. 18 American Wire Gage (AWG) color--coded, insulated
(35_C minimum) wires to make the control voltage connections
between the thermostat and the unit. If the thermostat is located
11

48VT-- A

4. All units must have field--supplied filters or accessory filter
rack installed in the return--air side of the unit.
Recommended sizes for filters are shown in Table 1.
5. Size all ductwork for maximum required airflow (either
heating or cooling) for unit being installed. Avoid abrupt
duct size increases or decreases or performance may be
affected.
6. Adequately insulate and weatherproof all ductwork located
outdoors. Insulate ducts passing through unconditioned
space, and use vapor barrier in accordance with latest issue
of Sheet Metal and Air Conditioning Contractors National
Association (SMACNA) and Air Conditioning Contractors
of America (ACCA) minimum installation standards for
heating and air conditioning systems. Secure all ducts to
building structure.
7. Flash, weatherproof, and vibration--isolate all openings in
building structure in accordance with local codes and good
building practices.

more than 100 ft (30.5 m) from the unit (as measured along the
control voltage wires), use no. 16 AWG color--coded, insulated
(35_C minimum) wires.
Locate the seven (eight on 3--phase) low voltage thermostat leads
in 24 volt splice box. See Fig. 10 for connection diagram. Run the
low--voltage leads from the thermostat, through the control wiring
inlet hole grommet (Fig. 2 and 3), and into the low--voltage splice
box. Provide a drip loop before running wires through panel.
Secure and strain relief all wires so that they do not interfere with
operation of unit. A gray wire is standard on 3--phase unit for
connection to an economizer.

48VT-- A

Transformer Protection
The transformer is of the energy--limiting type. It is set to withstand
a 30--sec. overload or shorted secondary condition. If an overload
or short is present, correct overload condition and check for blown
fuse on gas control board or Interface Fan Board. Replace fuse as
required with correct size and rating.

PRE--START--UP

HIGH VOLTAGE
POWER LEADS
(SEE UNIT WIRING
LABEL)

EQUIP GR

3. Comfort Balance Temperature: When the heat pump is
operating below this point, the indoor supply air feels
uncomfortable (i.e. too cool). This is purely subjective and
will depend on the homeowner’s idea of comfort. Below
this temperature the gas furnace should operate in order to
satisfy the desire for indoor comfort.

POWER
SUPPLY

FIRE, EXPLOSION, ELECTRICAL SHOCK HAZARD

FIELD-SUPPLIED
FUSED DISCONNECT

Failure to follow this warning could result in personal injury,
death or property damage.
1. Follow recognized safety practices and wear protective
goggles when checking or servicing refrigerant system.
2. Do not operate compressor or provide any electric power
to unit unless compressor terminal cover is in place and
secured.
3. Do not remove compressor terminal cover until all
electrical sources are disconnected and tagged.
4. Relieve and recover all refrigerant from system before
touching or disturbing anything inside terminal box if
refrigerant leak is suspected around compressor
terminals.
5. Never attempt to repair soldered connection while
refrigerant system is under pressure.
6. Do not use torch to remove any component. System
contains oil and refrigerant under pressure.
To remove a component, wear protective goggles and
proceed as follows:
a. Shut off electrical power to unit and install lockout
tag.
b. Relieve and reclaim all refrigerant from system
using both high-- and low--pressure ports.
c. Cut component connecting tubing with tubing
cutter and remove component from unit.
d. Carefully unsweat remaining tubing stubs when
necessary. Oil can ignite when exposed to torch
flame.

CONTROL BOX
WHT(W1)
YEL(Y)
GRN(G)
RED(R)
LOW-VOLTAGE
POWER LEADS
(SEE UNIT
WIRING LABEL)

BRN(C)

W
Y
G
R

THERMOSTAT
(TYPICAL)

ORN(O)
O
BLU (DH)
GRA (Y2)

WARNING

DH
3-Phase
Only

SPLICE BOX

A09067

Fig. 10 -- High and Control--Voltage Connections

Balance Point Setting-- Thermidistat or Hybrid
Thermostat
BALANCE POINT TEMPERATURE--The “balance point”
temperature is a setting which affects the operation of the heating
mode. This is a field--selected input temperature (range 5 to 55_F)
(--15 to 12_C) where the Thermidistat or dual fuel thermostat will
monitor outdoor air temperature and decide whether to enable or
disable the heat pump. If the outdoor temperature is above the
“balance point”, the heat pump will energize first to try to satisfy
the indoor temperature demand. If the heat pump does not make a
sufficient improvement within a reasonable time period (i.e. 15
minutes), then the gas furnace will come on to satisfy the indoor
temperature demand. If the outdoor temperature is below the
“balance point”, the heat pump will not be allowed to operate (i.e.
locked out), and the gas furnace will be used to satisfy the indoor
temperature. There are three separate concepts which are related to
selecting the final “balance point” temperature. Read each of the
following carefully to determine the best “balance point” in a
hybrid installation:
1. Capacity Balance Temperature: This is a point where the
heat pump cannot provide sufficient capacity to keep up
with the indoor temperature demand because of declining
outdoor temperature. At or below this point, the furnace is
needed to maintain proper indoor temperature.
2. Economic Balance Temperature: Above this point, the heat
pump is the most cost efficient to operate, and below this
point the furnace is the most cost efficient to operate. This
can be somewhat complicated to determine and it involves
knowing the cost of gas and electricity, as well as the
efficiency of the furnace and heat pump. For the most
economical operation, the heat pump should operate above
this temperature (assuming it has sufficient capacity) and the
furnace should operate below this temperature.

Proceed as follows to inspect and prepare the unit for initial
start--up:
1. Remove access panels (see Fig. 19).
2. Read and follow instructions on all WARNING,
CAUTION, and INFORMATION labels attached to, or
shipped with, unit.
3. Make the following inspections:
a. Inspect for shipping and handling damages such as
broken lines, loose parts, disconnected wires, etc.
b. Inspect for oil at all refrigerant tubing connections and
on unit base. Detecting oil generally indicates a
refrigerant leak.
c. Leak test all refrigerant tubing connections using
electronic leak detector, halide torch, or liquid--soap
solution. If a refrigerant leak is detected, see the Check
for Refrigerant Leaks section.
d. Inspect all field-- and factory--wiring connections. Be
sure that connections are completed and tight.

WARNING

FIRE, EXPLOSION HAZARD
Failure to follow this warning could result in personal injury,
death or property damage.
Do not purge gas supply into the combustion chamber. Do not
use a match or other open flame to check for gas leaks. Use a
commercially available soap solution made specifically for
the detection of leaks to check all connections.
4. Verify the following conditions:
a. Make sure gas line is free of air. Before lighting the unit
for the first time, perform the following with the gas
valve in the “OFF” position:
NOTE: If the gas supply pipe was not purged before connecting
the unit, it will be full of air. It is recommended that the ground
joint union be loosened, and the supply line be allowed to purge
until the odor of gas is detected. Never purge gas lines into a
combustion chamber. Immediately upon detection of gas odor,
retighten the union. Allow 5 minutes to elapse, then light unit.
b. Make sure that condenser--fan blade is correctly
positioned in fan orifice. Leading edge of condenser--fan
blade should be 1/2 in. (12 mm) maximum from fan
orifice.
c. Make sure that air filter(s) is in place.
d. Make sure that condensate drain trap is filled with water
to ensure proper drainage.
e. Make sure that all tools and miscellaneous loose parts
have been removed.

START--UP
Step 1 — Check for Refrigerant Leaks
Proceed as follows to locate and repair a refrigerant leak and to
charge the unit:
1. Locate leak and make sure that refrigerant system pressure
has been relieved and reclaimed from both high-- and
low--pressure ports.
2. Repair leak following Refrigerant Service procedures.
NOTE: Install a bi--flow filter drier whenever the system has been
opened for repair.
3. Add a small charge of R--410A refrigerant vapor to system
and leak--test unit.
4. Recover refrigerant from refrigerant system and evacuate to
500 microns if no additional leaks are not found.
5. Charge unit with Puron (R--410A) refrigerant, using an
electronic scale. Refer to unit rating plate for required
charge.

Step 2 — Unit Sequence of Operation
48VT-- A Sequence of Operation
a. CONTINUOUS FAN
(1.) Thermostat closes circuit R to G energizing the
blower motor for continuous fan.
b. COOLING MODE
(1.) If indoor temperature is above temperature set
point thermostat closes circuits R to G, R to Y and
R to O--The unit delivers cooling airflow.
c. HEAT PUMP HEATING MODE
Outdoor temperature above balance point setpoint of
thermostat.

Heating Sequence of Operation
(See Fig. 15 and 16 and unit wiring label.)
On a call for heating, terminal W of the thermostat is energized,
starting the induced--draft motor. When the pressure switch senses
that the induced--draft motor is moving sufficient combustion air,
the burner sequence begins. This function is performed by the
integrated gas unit controller (IGC). The indoor (evaporator)--fan
motor is energized 45 sec after flame is established. When the
thermostat is satisfied and W is de--energized, the burners stop
firing and the indoor (evaporator) fan motor shuts off after a
45--sec time--off delay. Please note that the IGC has the capability
to automatically reduce the indoor fan motor on delay and increase
the indoor fan motor off delay in the event of high duct static
and/or partially--clogged filter.
NOTE: An LED (light--emitting diode) indicator is provided on
the control board to monitor operation. The control board is
located by removing the burner access panel (see Fig. 19). During
normal operation, the LED is continuously on.

Step 3 — Start--up Heating and Make Adjustments

CAUTION

UNIT COMPONENT DAMAGE HAZARD
Failure to follow this caution may result in damage to the unit
being installed.
Complete the required procedures given in the Pre--Start--Up
section before starting the unit. Do not jumper any safety
devices when operating the unit.
Complete the required procedures given in the Pre--Start--Up
section before starting the unit. Do not jumper any safety devices
when operating the unit. Make sure that burner orifices are
properly aligned. Unstable operation my occur when the burner
orifices in the manifold are misaligned.
Follow the lighting instructions on the heating section operation
label (located on the inside of the control access panel) to start the
heating section.
NOTE: Make sure that gas supply has been purged, and that all
gas piping has been checked for leaks.

48VT-- A

(1.) On a call for heating, terminals “Y” and “G“ of the
Hybrid thermostat are energized. The “Y“ signal is
sent to the Defrost Board (DB) terminal “Y”. The
DB has a built in five minute anti--short cycle timer
which will not allow the compressor to restart
before the time delay has expired.
(2.) “T2” energizes the compressor contactor via the
High Pressure Switch (HPS) and Low Pressure
Switch (LPS). The compressor and outdoor fan
start. Thermostat “G” energizes the Interface Fan
Board terminal “G”. The blower motor is energized
through contacts of the IFB.
(3.) When the thermostat removes the “Y” and “G”
calls, the compressor contactor and outdoor fan are
de--energized. The evaporator motor is de--energized after a 90 sec. delay.
d. GAS HEATING MODE
Outdoor temperature below balance point setpoint of
thermostat.

e. Ensure wires do not touch refrigerant tubing or sharp
sheet metal edges.
f. Inspect coil fins. If damaged during shipping and
handling, carefully straighten fins with a fin comb.

specific gravity, or propane gas with a heating value of 2500
Btu/ft3 at 1.5 specific gravity.
IN THE U.S.A.:
The input rating for altitudes above 2,000 ft (610 m) must be
reduced by 4% for each 1,000 ft (305 m) above see level.
For installations below 2,000 ft (610 m), refer to the unit rating
plate.
For installations above 2,000 ft (610 m) multiply the input by on
the rating plate by the derate multiplier in Table 4 for correct input
rate.
Table 4 – Altitude Derate Multiplier for U.S.A.*

Pipe Plug

Manifold
A07679

Fig. 11 -- Burner Assembly

48VT-- A

BURNER FLAME

BURNER

MANIFOLD

C99021

Fig. 12 -- Monoport Burner

Check Heating Control
Start and check the unit for proper heating control operation as
follows (see furnace lighting instructions located on the inside of
the control access panel):
1. Place room thermostat SYSTEM switch in the HEAT
position and the fan switch is placed in AUTO position.
2. Set the heating temperature control of the thermostat above
room temperature.
3. The induced--draft motor will start.
4. On a call for heating, the main burner should light within 5
sec. of the spark being energized. If the burners do not light,
there is a 22--sec. delay before another 5--sec. try. If the
burners still do not light, this sequence is repeated. If the
burners do not light within 15 minutes from the initial call
for heat, there is a lockout. To reset the control, break the
24--v power to W.
5. The evaporator fan will turn on 45 sec. after the flame has
been established. The evaporator fan will turn off 45 sec.
after the thermostat has been satisfied. Please note that the
integrated gas unit controller (IGC) has the capability to
automatically reduce the evaporator “ON” delay and increase the evaporator “OFF” delay in the event of high duct
static and/or partially--clogged filter.

Check Gas Input
Check gas input and manifold pressure after unit start--up (See
Table 3). If adjustment is required proceed as follows:
S The rated gas inputs shown in Table 3 are for altitudes from sea
level to 2000 ft (610 m) above sea level. These inputs are based
on natural gas with a heating value of 1025 Btu/ft3 at 0.60

ALTITUDE FT (M)

PERCENT OF DERATE

DERATE MULTIPLIER
FACTOR{

0--- 2000
(0--- 610)

1.00

2001--- 3000*
(610--- 914)

8--- 12

0.90

3001--- 4000
(315--- 1219)

12--- 16

0.86

4001--- 5000
(1220--- 1524)

16--- 20

0.82

5001--- 6000
(1524--- 1829)

20--- 24

0.78

6001--- 7000
(1829--- 2134)

24--- 28

0.74

7001--- 8000
(2134--- 2438)

28--- 32

0.70

8001--- 9000
(2439--- 2743)

32--- 36

0.66

9001--- 10,000
(2744--- 3048)

36--- 40

0.62

* In Canada see Canadian Altitude Adjustment.
{Derate multiplier factors are based on midpoint altitude for altitude range.

IN CANADA:
The input rating for altitudes from 2,000 to 4,500 ft (610 m to
1372 m) above sea level must be derated 10% by an authorized
Gas Conversion Station or Dealer.
EXAMPLE:
90,000 Btu/hr Input Furnace Installed at 4300 ft (1311 m).
Furnace Input Rate at
Sea Level
90,000

X Derate Multiplier
Factor

= Furnace Input Rate at
Installation Altitude

0.90

81,000

When the gas supply being used has a different heating value or
specific gravity, refer to national and local codes, or contact your
distributor to determine the required orifice size.

CAUTION

UNIT DAMAGE HAZARD
Failure to follow this caution may result in reduced unit
and/or component life.
Do Not redrill an orifice. Improper drilling (burrs,
out--of--round holes, etc.) can cause excessive burner noise
and misdirection of burner flame. If orifice hole appears
damaged or it is suspected to have been redrilled, check
orifice hole with a numbered drill bit of correct size.

Adjust Gas Input
The gas input to the unit is determined by measuring the gas flow
at the meter or by measuring the manifold pressure. Measuring the
gas flow at the meter is recommended for natural gas units. The
manifold pressure must be measured to determine the input of
propane gas units.
Measure Gas Flow (Natural Gas Units)
Minor adjustment to the gas flow can be made by changing the
manifold pressure. The manifold pressure must be maintained
between 3.2 and 3.8 IN. W.C.
14

REGULATOR
COVER SCREW

PLASTIC
ADJUSTMENT
SCREW

FIRE AND UNIT DAMAGE HAZARD

ON/OFF SWITCH

Failure to follow this warning could result in personal
injury or death and/or property damage.

REGULATOR SPRING
(PROPANE - WHITE)
(NATURAL - SILVER)

Unsafe operation of the unit may result if manifold pressure
is outside this range.

GAS PRESSURE
REGULATOR
ADJUSTMENT

MANIFOLD
PRESSURE TAP

A07751

Fig. 13 -- Single--Stage Gas Valve
If larger adjustments are required, change main burner orifices
following the recommendations of national and local codes.
NOTE: All other appliances that use the same meter must be
turned off when gas flow is measured at the meter.
Proceed as follows:
1. Turn off gas supply to unit.
2. Remove pipe plug on manifold (See Fig. 11) and connect
manometer. Turn on gas supply to unit.
3. Record number of seconds for gas meter test dial to make
one revolution.
4. Divide number of seconds in Step 3 into 3600 (number of
seconds in one hr).
5. Multiply result of Step 4 by the number of cubic feet (cu ft)
shown for one revolution of test dial to obtain cubic feet (cu
ft) of gas flow per hour.
6. Multiply result of Step 5 by Btu heating value of gas to
obtain total measured input in Btuh. Compare this value
with heating input shown in Table 3 (Consult the local gas
supplier if the heating value of gas is not known).
EXAMPLE: Assume that the size of test dial is 1 cu ft, one
revolution takes 32 sec, and the heating value of the gas is 1050
Btu/ft3. Proceed as follows:
1. 32 sec. to complete one revolution.
2. 3600 ÷ 32 = 112.5.
3. 112.5 x 1 =112.5 ft3 of gas flow/hr.
4. 112.5 x 1050 = 118,125 Btuh input.
If the desired gas input is 115,000 Btuh, only a minor change in the
manifold pressure is required.
Observe manifold pressure and proceed as follows to adjust gas
input:
1. Remove regulator cover screw over plastic adjustment
screw on gas valve (See Fig. 13).
2. Turn plastic adjustment screw clockwise to increase gas
input, or turn plastic adjustment screw counterclockwise to
decrease input (See Fig. 13). Manifold pressure must be
between 3.2 and 3.8 IN. W.C.

3. Replace regulator cover screw on gas valve (See Fig. 13).
4. Turn off gas supply to unit. Remove manometer from
pressure tap and replace pipe plug on gas valve. (See Fig.
11.) Turn on gas to unit and check for leaks.
Measure Manifold Pressure (Propane Units)
Refer to propane kit installation instructions for properly checking
gas input.
NOTE: For installations below 2,000 ft (610 m), refer to the unit
rating plate for proper propane conversion kit. For installations
above 2,000 ft (610 m), contact your distributor for proper propane
conversion kit.

Check Burner Flame
With control access panel (see Fig. 19) removed, observe the unit
heating operation. Watch the burner flames to see if they are light
blue and soft in appearance, and that the flames are approximately
the same for each burner. Propane will have blue flame (See Fig.
12). Refer to the Maintenance section for information on burner
removal.

Normal Operation
An LED (light--emitting diode) indicator is provided on the
integrated gas unit controller (IGC) to monitor operation. The IGC
is located by removing the control access panel (see Fig. 19).
During normal operation, the LED is continuously on (See Table 5
for error codes).

Airflow and Temperature Rise
The heating section for each size unit is designed and approved for
heating operation within the temperature--rise range stamped on the
unit rating plate.
Table 10 shows the approved temperature rise range for each
heating input, and the air delivery cfm at various temperature rises
for a given external static pressure. The heating operation airflow
must produce a temperature rise that falls within the approved
range.
Refer to Indoor Airflow and Airflow Adjustments section to adjust
heating airflow when required.

Limit Switches
Normally closed limit switch (LS) completes the control circuit.
Should the leaving--air temperature rise above the maximum
allowable temperature, the limit switch opens and the control
circuit “breaks.” Any interruption in the control circuit instantly
closes the gas valve and stops gas flow to the burners and pilot.
The blower motor continues to run until LS resets.
When the air temperature at the limit switch drops to the
low--temperature setting of the limit switch, the switch closes and

48VT-- A

INLET
PRESSURE TAP

WARNING

completes the control circuit. The direct--spark ignition system
cycles and the unit returns to normal heating operation.
Table 5 – LED Indications

48VT-- A

STATUS CODE
Normal Operation2
No Power Hardware Failure
Limit Switch Fault
Flame Sense Fault
Four Consecutive Limit Switch Faults
Ignition Lockout Fault
Pressure Switch Fault
Rollout Switch Fault
Internal Control Fault
Temporary 1 hr auto reset1

LED INDICATION
On
Off
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes
7 Flashes
8 Flashes
9 Flashes

NOTE: Adjustment of the refrigerant charge is not required unless
the unit is suspected of not having the proper PuronR (R--410A)
charge.
The charging label and the tables shown refer to system
temperatures and pressures in cooling mode only. A refrigerant
charging label is attached to the inside of the compressor access
panel (see Fig. 19). The chart includes the required liquid line
temperature at given discharge line pressures and outdoor ambient
temperatures.
An accurate thermocouple-- or thermistor--type thermometer, and a
gauge manifold are required when using the subcooling charging
method for evaluating the unit charge. Do not use mercury or small
dial--type thermometers because they are not adequate for this type
of measurement.

NOTES:
1.This code indicates an internal processor fault that will reset itself in one
hr. Fault can be caused by stray RF signals in the structure or nearby. This
is a UL requirement.
2. LED indicates acceptable operation. Do not change ignition control
board.
3. When W is energized the burners will remain on for a minimum of 60 sec.
4. If more than one error mode exists they will be displayed on the LED in
sequence.

UNIT DAMAGE HAZARD
Failure to follow this caution may result in unit damage.
When evaluating the refrigerant charge, an indicated
adjustment to the specified factory charge must always be
very minimal. If a substantial adjustment is indicated, an
abnormal condition exists somewhere in the cooling system,
such as insufficient airflow across either coil or both coils.

Rollout Switch
The function of the rollout switch is to close the main gas valve in
the event of flame rollout. The switch is located above the main
burners. When the temperature at the rollout switch reaches the
maximum allowable temperature, the control circuit trips, closing
the gas valve and stopping gas flow to the burners. The indoor
(evaporator) fan motor (IFM) and induced draft motor continue to
run until switch is reset. The IGC LED will display FAULT CODE
7.

Step 4 — Start--up Cooling and Make Adjustments
Complete the required procedures given in the Pre--Start--Up
section before starting the unit. Do not jumper any safety devices
when operating the unit. Do not operate the compressor when the
outdoor temperature is below 40°F (4.4°C) (unless accessory
low--ambient kit is installed). Do not rapid--cycle the compressor.
Allow 5 minutes between on cycles to prevent compressor damage.

Checking Cooling Control Operation
Start and check the unit for proper cooling control operation as
follows:
1. Place room thermostat SYSTEM switch in OFF position.
Observe that blower motor starts when FAN switch is
placed in ON position and shuts down when FAN switch is
placed in AUTO position.
2. Place SYSTEM switch in COOL position and FAN switch
in AUTO position. Set cooling control below room
temperature. Observe that compressor, condenser fan, and
evaporator blower motors start. Observe that cooling cycle
shuts down when control setting is satisfied. The evaporator
fan will continue to run for 90 sec.
IMPORTANT:
Three--phase, scroll compressors units are
direction oriented. Unit must be checked to ensure proper
compressor 3--phase power lead orientation. If not corrected within
5 minutes, the internal protector will shut off the compressor. The
3--phase power leads to the unit must be reversed to correct
rotation. When turning backwards, the difference between
compressor suction and discharge pressures will be near zero.

Proceed as follows:
1. Remove caps from low-- and high--pressure service fittings.
2. Using hoses with valve core depressors, attach low-- and
high--pressure gauge hoses to low-- and high--pressure
service fittings, respectively.
3. Start unit in Cooling Mode and let unit run until system
pressures stabilize.
4. Measure and record the following:
a. Outdoor ambient--air temperature (°F (°C) db).
b. Liquid line temperature (°F (°C).
c. Discharge (high--side) pressure (psig).
d. Suction (low--side) pressure (psig) (for reference only).
5. Using “Cooling Charging Charts,” compare outdoor--air
temperature(°F (°C) db) with the discharge line pressure
(psig) to determine desired system operating liquid line
temperature (See Fig. 17).
6. Compare actual liquid line temperature with desired liquid
line temperature. Using a tolerance of ± 2°F (±1.1°C), add
refrigerant if actual temperature is more than 2°F (1.1°C)
higher than proper liquid line temperature, or remove
refrigerant if actual temperature is more than 2°F (1.1°C)
lower than required liquid line temperature.
NOTE: If the problem causing the inaccurate readings is a
refrigerant leak, refer to the Check for Refrigerant Leaks section.

Indoor Airflow and Airflow Adjustments

CAUTION

UNIT OPERATION HAZARD
Failure to follow this caution may result in unit damage.
For cooling operation, the recommended airflow is 350 to
450 cfm for each 12,000 Btuh of rated cooling capacity. For
heating operation, the airflow must produce a temperature
rise that falls within the range stamped on the unit rating
plate.

Checking and Adjusting Refrigerant Charge
The refrigerant system is fully charged with PuronR (R--410A)
refrigerant and is tested and factory sealed. Allow system to operate
a minimum of 15 minutes before checking or adjusting charge.

CAUTION

NOTE: Be sure that all supply--and return--air grilles are open,
free from obstructions, and adjusted properly.
16

WARNING

ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
Before making any indoor wiring adjustments, shut off gas
supply. Then disconnect electrical power to the unit and
install lockout tag before changing blower speed.
This unit has independent fan speeds for gas heating and cooling.
In addition, this unit has the field-selectable capability to run two
different cooling fan speeds: A normal cooling fan speed (350~400
CFM/Ton) and an enhanced dehumidification fan speed (As low as
320 CFM/Ton) for use with either a dehumidistat or a thermostat
that supports dehumidification.
This unit is factory-set up for use with a single cooling fan speed.
The cooling speed is marked “LOW” on the interface fan board
(IFB) (Fig. 14) . The factory-shipped settings are noted in Table
10. There are 3 additional speed tap wires available for use in
either gas heating or cooling (For color coding on the indoor fan
motor leads, see Table 6). The additional 3 speed tap wires are
shipped loose with vinyl caps and are located in the control box,
near the interface fan board (IFB) (Fig. 14).

Gas Heating Fan Speed Set-up
To change the gas heating speed:
1. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding). Table 10 shows the
temperature rise associated with each fan speed for a given
static pressure. Make sure that the speed chosen delivers a
temperature rise within the rise range listed on the unit
rating plate.
2. Remove the current speed tap wire from the “GAS HEAT”
terminal on the interface fan board (IFB) (Fig.14) and place
vinyl cap over the connector on the wire.
3. Connect the desired speed tap wire to the “GAS HEAT”
terminal on the interface fan board (IFB).

Single Cooling Fan Speed Set-up (Dehumidification
feature not used)
To change cooling speed:
1. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding). Add the wet coil
pressure drop in Table 8 to the system static to determine the
correct cooling airflow speed in Table 10 that will deliver
the nominal cooling airflow as listed in Table 1 for each
size.
2. Remove the current speed tap wire from the “LOW”
terminal on the interface fan board (IFB) (Fig. 14) and place
vinyl cap over the connector on the wire.

3. Connect the desired speed tap wire to the “LOW” terminal
on the interface fan board (IFB).

Two Cooling Fan Speeds Set-up (Dehumidification
feature used)
IMPORTANT: Dehumidification control must open control
circuit on humidity rise above set point.
Use of the dehumidification cooling fan speed requires use of
either a 24 VAC dehumidistat or a thermostat which includes
control of a 24 VAC dehumidistat connection. In either case, the
dehumidification control must open the control circuit on humidity
rise above the dehumidification set point. Dehumidification
controls are available with the reverse logic; these must not be
used.
1. Remove fan speed tap wire from the “LOW” terminal on
the interface fan board (IFB) (Fig. 14).
2. Determine correct normal cooling fan speed for unit and
application. Add the wet coil pressure drop in Table 8 to
the system static to determine the correct cooling airflow
speed in Table 10 that will deliver the nominal cooling
airflow as listed in Table 1 for each size.
3. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding) for the normal cooling
fan speed and place desired speed tap wire on “HIGH” on
the interface board.
4. Refer to airflow tables (Table 10) to determine allowable
speeds for the dehumidification cooling fan speed. In Table
10, speeds that are not allowed for dehumidification cooling
are shaded.
5. Remove the vinyl cap off of the desired speed tap wire
(Refer to Table 6 for color coding) for the dehumidification
cooling fan speed and place desired speed tap wire on the
“LOW” connection on the interface board (IFB). Verify
that static pressure is in the acceptable range for the speed
tap to be used for dehumidification cooling.
6. Use any spare vinyl plugs to cap any unused speed tap
wires.
NOTE: For heat pump operation, the recommended airflow is 350
to 450 CFM for each 12,000 Btuh of rated cooling capacity.

Continuous Fan Operation
When the DEHUM feature is not used, the continuous fan speed
will be the same as cooling fan speed. When the DEHUM feature
is used, the continuous fan will operate on IFB “LOW” speed
when the DH control lead is not energized, or IFB “HIGH” speed
when the DH lead is energized (see Fig. 14).
Table 6 – Color Coding for Indoor Fan Motor Leads
Black = High Speed
Orange = Med---High Speed
Red = Med Speed
Pink = Med---Low Speed
Blue = Low Speed

48VT-- A

QC6

LOW

QC7

QC4

RL3 C8

R1L

QCR

D2
QC1

JM6

RI2

G1JM5

3 AMP

DCR

OILL C2

QC3
K1

RI0

COM

D4
A7

CDM/C

HIGH

24VAC/R

GAS
HEAT

AB A15

F1
C0

U1
R4

48VT-- A

RL4

D5 D3
C7
JW3

R3 R5 R6

QCB

JW7

SDL

JW2
JW4

C 24VAC

JW1

SSTZ-8
Y1/
W2 Y2/
DH G Y C

A09058

Fig. 14 -- Interface Fan Board (IFB)
Table 7 – Filter Pressure Drop Table (IN. W.C.)
FILTER SIZE
in. (mm)
20X20X1
(508X508X25)
20X24X1
(508X610x25 )
24X30X1
(610X762x25)
24X36X1
(610X914X25)

500

600

700

800

900

1000

1100

1200

1300

CFM
1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

0.05

0.07

0.08

0.1

0.12

0.13

0.14

0.15

—

0.09

0.10

0.11

0.13

0.14

0.15

0.16

—

0.04

0.05

0.06

0.07

0.08

0.09

0.1

—

0.06

0.07

0.08

0.09

0.10

0.11

0.12

0.13

0.14

Table 8 – 48VT--A Wet Coil Pressure Drop
Unit Size
24
30
36
42
48
60

500

600
0.06

700
0.07

800
0.08
0.12

900
0.09
0.15

1000
0.1
0.19
0.07

Standard CFM (S.C.F.M)
1100
1200
1300
1400
0.23
0.11

0.27
0.18
0.04

0.26
0.07

0.35
0.1
0.11

1500

1600

1700

1800

1900

2000

0.15
0.14

0.21
0.17
0.1

0.22
0.17

0.28
0.23

0.31

0.36

Table 9 – Wet Coil Air Delivery - Downflow -- High Speed with 1--in. Filter and Economizer
UNIT SIZE

36, 42
48
60

0.1

1612
2298
2000

0.2

1569
2239
1926

0.3

1527
2180
1825

EXTERNAL STATIC PRESSURE (in. W.C.)
0.4
0.5
0.6
0.7

1481
2110
1820

1451
2044
1759

1393
1951
1705

1351
1862
1634

0.8

1317
1777
1496

0.9

1278
1697
1412

1.0

1242
1591
1328

Table 10 – Dry Coil Air Delivery* -- Horizontal and Downflow Discharge -- Unit 48VT--A24--60
HEATING
RISE
RANGE

MOTOR
SPEED

Low

Med-Low2

48VT(-,N)A24040

30 - 60oF
(17 - 33oC)

Medium1

Med-High

High

Low

Med-Low2

48VT(-,N)A24060

25 - 55oF
(14 - 31oC)

Medium

Med-High

High1

Low

Med-Low

48VT(-,N)A30040

30 - 60oF
(17 - 33oC)

Medium1

Med-High2

High

EXTERNAL STATIC PRESSURE (in. W.C.)

WIRE
COLOR

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)
CFM
Heating
Rise (oF)
Heating
Rise (oC)

0.1
741

0.2
638

0.3
547

0.4
415

0.5
---

0.6
---

0.7
---

0.8
---

0.9
---

NA
NA

898

820

738

662

536

---

NA
NA

973

887

823

733

665

538

451

---

1140

1064

996

915

840

758

687

564

480

1202

1140

1082

1015

961

881

810

732

631

48
27

741

638

547

415

---

NA
NA

898

820

738

662

536

---

NA
NA

973

887

823

733

665

538

451

---

1140

1064

996

915

840

758

687

564

480

1202

1140

1082

1015

961

881

810

732

631

NA
NA

741

638

547

415

---

NA
NA

898

820

738

662

536

---

NA
NA

973

887

823

733

665

538

451

---

1140

1064

996

915

840

758

687

564

480

1202

1140

1082

1015

961

881

810

732

631

48VT-- A

UNIT

Table 10 -- Dry Coil Air Delivery* -- Horizontal and Downflow Discharge -- Unit 48VT--A24--60 Cont
UNIT

HEATING
RISE
RANGE

MOTOR
SPEED

Low

Med-Low

48VT(-,N)A30060

25 - 55oF
(14 - 31oC)

Medium

48VT-- A

Med-High2

High1

Low1

Med-Low

48VT(-,N)A36060

25 - 55oF
(14 - 31oC)

Medium

Med-High2

High

Low

Med-Low

48VT(-,N)A36090

35 - 65oF
(19 - 36oC)

Medium1

Med-High2

High

EXTERNAL STATIC PRESSURE (in. W.C.)

WIRE
COLOR

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

741

638

547

415

---

0.9
---

NA
NA

898

820

738

662

536

---

NA
NA

973

887

823

733

665

538

451

---

1140

1064

996

915

840

758

687

564

480

1202

1140

1082

1015

961

881

810

732

631

1295

1234

1182

1126

1075

1016

955

898

857

1345

1282

1235

1194

1140

1095

1027

974

921

1505

1452

1413

1358

1323

1282

1234

1169

1130

1545

1492

1449

1411

1362

1313

1278

1231

1188

1705

1643

1607

1568

1518

1483

1448

1404

1360

1295

1234

1182

1126

1075

1016

955

898

857

1345

1282

1235

1194

1140

1095

1027

974

921

1505

1452

1413

1358

1323

1282

1234

1169

1130

1545

1492

1449

1411

1362

1313

1278

1231

1188

1705

1643

1607

1568

1518

1483

1448

1404

1360

Table 10 -- Dry Coil Air Delivery* -- Horizontal and Downflow Discharge -- Unit 48VT--A24--60 Cont
HEATING
RISE
RANGE

MOTOR
SPEED

Low1

Med-Low

48VT(-,N)A42060

25 - 55oF
(14 - 31oC)

Medium

Med-High2

High

Low

Med-Low

48VT(-,N)A42090

35 - 65oF
(19 - 36oC)

Medium1

Med-High2

High

Low1

Med-Low2

48VT(-,N)A48090

35 - 65oF
(19 - 36oC)

Medium

Med-High

High

EXTERNAL STATIC PRESSURE (in. W.C.)

WIRE
COLOR

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1295

1234

1182

1126

1075

1016

955

898

857

1345

1282

1235

1194

1140

1095

1027

974

921

1505

1452

1413

1358

1323

1282

1234

1169

1130

1545

1492

1449

1411

1362

1313

1278

1231

1188

1705

1643

1607

1568

1518

1483

1448

1404

1360

1295

1234

1182

1126

1075

1016

955

898

857

1345

1282

1235

1194

1140

1095

1027

974

921

1505

1452

1413

1358

1323

1282

1234

1169

1130

1545

1492

1449

1411

1362

1313

1278

1231

1188

1705

1643

1607

1568

1518

1483

1448

1404

1360

1445

1389

1341

1281

1236

1189

1139

1072

1027

1678

1635

1602

1558

1513

1474

1438

1404

1349

1962

1915

1880

1843

1794

1753

1711

1675

1628

2131

2088

2065

2013

1982

1941

1888

1860

1785

2461

2409

2339

2286

2192

2140

2062

1968

1874

48VT-- A

UNIT

Table 10 -- Dry Coil Air Delivery* -- Horizontal and Downflow Discharge -- Unit 48VT--A24--60 Cont
UNIT

HEATING
RISE
RANGE

MOTOR
SPEED

Low

Med-Low2

48VT(-,N)A48115

30 - 60oF
(17 - 33oC)

Medium

48VT-- A

Med-High1

High

Low

Med-Low2

48VT(-,N)A48130

35 - 65oF
(19 - 36oC)

Medium

Med-High1

High

Low1

Med-Low

48VT(-,N)A60090

35 - 65oF
(19 - 36oC)

Medium2

Med-High

High

EXTERNAL STATIC PRESSURE (in. W.C.)

WIRE
COLOR

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

Blue

Pink

Red

Orange

Black

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1445

1389

1341

1281

1236

1189

1139

1072

1027

1678

1635

1602

1558

1513

1474

1438

1404

1349

1962

1915

1880

1843

1794

1753

1711

1675

1628

2131

2088

2065

2013

1982

1941

1888

1860

1785

2461

2409

2339

2286

2192

2140

2062

1968

1874

1445

1389

1341

1281

1236

1189

1139

1072

1027

1678

1635

1602

1558

1513

1474

1438

1404

1349

1962

1915

1880

1843

1794

1753

1711

1675

1628

2131

2088

2065

2013

1982

1941

1888

1860

1785

2461

2409

2339

2286

2192

2140

2062

1968

1874

1448

1362

1296

1226

1168

1108

1071

998

905

1722

1675

1614

1543

1499

1442

1408

1356

1308

1887

1847

1783

1726

1677

1625

1578

1527

1432

2055

2008

1958

1927

1900

1768

1685

1581

1458

2292

2238

2158

2049

1935

1840

1732

1635

1513

Table 10 -- Dry Coil Air Delivery* -- Horizontal and Downflow Discharge -- Unit 48VT--A24--60 Cont
HEATING
RISE
RANGE

MOTOR
SPEED

WIRE
COLOR

EXTERNAL STATIC PRESSURE (in. W.C.)
0.1

0.2

0.3

0.4

0.5

0.6

CFM
1448
1362
1296
1226
1168
1108
Heating
60
NA
NA
NA
NA
NA
o
Rise ( F)
Low
Blue
Heating
33
NA
NA
NA
NA
NA
Rise (oC)
CFM
1722
1675
1614
1543
1499
1442
Heating
50
52
54
56
58
60
Rise (oF)
Med-Low
Pink
Heating
28
29
30
31
32
33
Rise (oC)
CFM
1887
1847
1783
1726
1677
1625
Heating
46
47
49
50
52
53
30 - 60oF
Rise (oF)
48VT(-,N)A60115
Medium2
Red
(17 - 33oC)
Heating
26
26
27
28
29
30
Rise (oC)
CFM
2055
2008
1958
1927
1900
1768
Heating
42
43
44
45
46
49
Rise (oF)
Med-High1
Orange
Heating
23
24
25
25
25
27
Rise (oC)
CFM
2292
2238
2158
2049
1935
1840
Heating
38
39
40
42
45
47
Rise (oF)
High
Black
Heating
21
22
22
24
25
26
Rise (oC)
CFM
1448
1321
1282
1235
1192
1145
Heating
NA
NA
NA
NA
NA
NA
Rise (oF)
Low
Blue
Heating
NA
NA
NA
NA
NA
NA
Rise (oC)
CFM
1722
1675
1614
1543
1499
1442
Heating
56
57
60
62
64
NA
Rise (oF)
Med-Low
Pink
Heating
31
32
33
35
36
NA
Rise (oC)
CFM
1887
1847
1783
1726
1677
1625
Heating
51
52
54
56
57
59
35 - 65oF
Rise (oF)
48VT(-,N)A60130
Medium2
Red
(19 - 36oC)
Heating
28
29
30
31
32
33
Rise (oC)
CFM
2055
2008
1958
1927
1900
1768
Heating
47
48
49
50
51
54
Rise (oF)
Med-High1
Orange
Heating
26
27
27
28
28
30
Rise (oC)
CFM
2292
2238
2158
2049
1935
1840
Heating
42
43
45
47
50
52
Rise (oF)
High
Black
Heating
23
24
25
26
28
29
Rise (oC)
* Air delivery values are without air filter and are for dry coil (See 48VT ---A Wet Coil Pressure Drop table).
1 Factory ---shipped gas heating speed
2 Factory ---shipped heat pump speed
NA --- Not allowed for heating speed
Note: Deduct field---supplied air filter pressure drop and wet coil pressure drop to obtain external static pressure available for ducting.
Shaded areas indicate speed/static combinations that are not permitted for dehumidification speed.

0.7

0.8

0.9

1071

998

905

1408

1356

1308

1578

1527

1432

1685

1581

1458

1732

1635

1513

1101

1057

1011

1408

1356

1308

1578

1527

1432

1685

1581

1458

1732

1635

1513

48VT-- A

UNIT

48VT-- A

A09068

Fig. 15 -- 208/230--1--60 Wiring Diagram, Unit 48VT--A

48VT-- A
A09209

Fig. 16 -- 208/230--3--60 Wiring Diagram, Unit 48VT--A

50VT500173 REV 4.0

48VT-- A

A09099

Fig. 17 -- Cooling Charging Table--Subcooling

MAINTENANCE

WARNING

PERSONAL INJURY AND UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal injury
or death and unit component damage.
The ability to properly perform maintenance on this
equipment requires certain expertise, mechanical skills, tools
and equipment. If you do not possess these, do not attempt to
perform any maintenance on this equipment, other than those
procedures recommended in the Owner’s Manual.

Air Filter
IMPORTANT: Never operate the unit without a suitable air filter
in the return--air duct system. Always replace the filter with the
same dimensional size and type as originally installed. (See Table 1
for recommended filter sizes.)
Inspect air filter(s) at least once each month and replace
(throwaway--type) or clean (cleanable--type) at least twice during
each heating and cooling season or whenever the filter(s) becomes
clogged with dust and/or lint.

Indoor Blower and Motor
NOTE: All motors are prelubricated. Do not attempt to lubricate
these motors.
For longer life, operating economy, and continuing efficiency,
clean accumulated dirt and grease from the blower wheel and
motor annually.

WARNING

ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.

ELECTRICAL SHOCK HAZARD
Failure to follow these warnings could result in personal
injury or death:
1. Turn off electrical power to the unit and install a lockout
tag before performing any maintenance or service on this
unit.
2. Use extreme caution when removing panels and parts.
3. Never place anything combustible either on or in contact
with the unit.
4. Should overheating occur or the gas supply fail to shut
off, turn off external main manual gas valve to the unit.
Then shut off electrical supply.

CAUTION

UNIT OPERATION HAZARD
Failure to follow this caution may result in improper
operation.
Errors made when reconnecting wires may cause improper
and dangerous operation. Label all wires prior to
disconnecting when servicing.
The minimum maintenance requirements for this equipment are as
follows:
1. Inspect air filter(s) each month. Clean or replace when
necessary. Certain geographical locations may require more
frequent inspections.
2. Inspect indoor coil, outdoor coil, drain pan, and condensate
drain each cooling season for cleanliness. Clean when
necessary.
3. Inspect blower motor and wheel for cleanliness at the
beginning of each heating and cooling season. Clean when
necessary. For first heating and cooling season, inspect
blower wheel bi--monthly to determine proper cleaning
frequency.
4. Check electrical connections for tightness and controls for
proper operation each heating and cooling season. Service
when necessary. Ensure electrical wiring is not in contact
with refrigerant tubing or sharp metal edges.

WARNING

Disconnect and tag electrical power to the unit before cleaning
the blower motor and wheel.
Cleaning the Blower Motor and Wheel
1. Remove and disassemble blower assembly as follows:
a. Remove blower access panel (see Fig. 19).
b. Disconnect 5 pin plug and 4 pin plug from indoor
blower motor. Remove capacitor if required.
c. On all units, remove blower assembly from unit.
Remove screws securing blower to blower partition and
slide assembly out. Be careful not to tear insulation in
blower compartment.
d. Ensure proper reassembly by marking blower wheel and
motor in relation to blower housing before disassembly.
e. Loosen setscrew(s) that secures wheel to motor shaft.
Remove screws that secure motor mount brackets to
housing, and slide motor and motor mount out of
housing.
2. Remove and clean blower wheel as follows:
a. Ensure proper reassembly by marking wheel orientation.
b. Lift wheel from housing. When handling and/or
cleaning blower wheel, be sure not to disturb balance
weights (clips) on blower wheel vanes.
c. Remove caked--on dirt from wheel and housing with a
brush. Remove lint and/or dirt accumulations from
wheel and housing with vacuum cleaner, using soft
brush attachment. Remove grease and oil with mild
solvent.
d. Reassemble wheel into housing.
e. Reassemble motor into housing. Be sure setscrews are
tightened on motor shaft flats and not on round part of
shaft. Reinstall blower into unit. Reinstall capacitor.
f. Connect 5 pin plug and 4 pin plug to indoor blower
motor.
g. Reinstall blower access panel (see Fig. 19).
3. Restore electrical power to unit. Start unit and check for
proper blower rotation and motor speeds during heating and
cooling cycles.

48VT-- A

To ensure continuing high performance and to minimize the
possibility of premature equipment failure, periodic maintenance
must be performed on this equipment. This combination
heating/cooling unit should be inspected at least once each year by
a qualified service person. To troubleshoot cooling or heating of
units, refer to Tables 10, 11 and 12.
NOTE: Consult your local dealer about the availability of a
maintenance contract.

5. Check and inspect heating section before each heating
season. Clean and adjust when necessary.
6. Check flue hood and remove any obstructions, if necessary.

directions in the Induced Draft Blower Assembly section.
2. Remove the 11 screws holding the flue collector box cover
(See Fig. 18) to the heat exchanger assembly. Inspect the
heat exchangers.
3. Clean all surfaces, as required, using a wire brush.

Integrated
Gas Unit
Controller
(IGC)
Auto Transformer
fuses used on 460
volt units only.
(Hidden)
Interface Fan
Board (IFB)

Remove blower access panel (see Fig. 19). Limit switch is located
on the fan partition.

Induced Draft
Motor

Fan Partition
Mounting
Bracket

Flue
Collector
Box

Inducer
Blower
Housing

Burner
Rack

Mounting
Screw

Limit Switch
Burner Ignition

Rollout
Switch

A09199

Fig. 18 -- Blower Housing and Flue Collector Box

Unit is equipped with a direct spark ignition 100 percent lockout
system. Ignition module (IGC) is located in the control box (See
Fig. 18). Module contains a self--diagnostic LED. During
servicing, refer to label diagram or Table 5 in these instructions for
LED interpretation.
If lockout occurs, unit may be reset by either momentarily
interrupting power supply to unit or by turning selector switch to
OFF position at the thermostat.

48VT-- A

Main Burners

Compressor
Access Panel

Blower
Access
Panel

Control
Access
Panel
A09210

Fig. 19 -- Unit Access Panels

Induced Draft (combustion air) Blower Assembly
The induced--draft blower assembly consists of the inducer motor,
the blower housing, and the induced--draft blower wheel.
Clean periodically to assure proper airflow and heating efficiency.
Inspect blower wheel every fall and periodically during the heating
season. For the first heating season, inspect blower wheel
bimonthly to determine proper cleaning frequency.
To inspect blower wheel, remove draft hood assembly. Shine a
flashlight into opening to inspect wheel. If cleaning is required,
remove induced--draft blower assembly as follows:
1. Remove control access panel (See Fig. 19).
2. Remove the 5 screws that attach induced--draft blower assembly to the flue collector box cover.
3. Slide the assembly out of the unit. (See Fig. 20). Clean the
blower wheel. If additional cleaning is required, continue
with Steps 4 and 5.
4. To remove blower wheel, remove 2 setscrews.
5. To remove inducer motor, remove screws that hold the
inducer motor to the blower housing.
6. To reinstall, reverse the procedure outlined above.

Flue Gas Passageways
To inspect the flue collector box and upper areas of the heat
exchanger:
1. Remove the induced draft blower assembly according to

At the beginning of each heating season, inspect for deterioration
or blockage due to corrosion or other causes. Observe the main
burner flames and adjust, if necessary.
Removal of Gas Train
To remove the gas train for servicing:
1. Shut off main gas valve.
2. Shut off power to unit and install lockout tag.
3. Remove control access panel (See Fig. 19).
4. Disconnect gas piping at unit gas valve.
5. Remove fan partition mounting bracket (2 screws located
on the left side of control compartment on the fan partition
panel). Slide bracket forward, bottom first to remove. (See
Fig. 18).
6. Remove wires connected to gas valve. Mark each wire.
7. Remove ignitor and sensor wires at the ignitor module.
8. Remove the mounting screw that attaches the burner rack to
the unit base (See Fig. 18).
9. Slide the burner rack out of the unit (See Fig. 18 and 21).
10. To reinstall, reverse the procedure outlined above.

Outdoor Coil, Indoor Coil, and Condensate Drain Pan
Inspect the outdoor coil, indoor coil, and condensate drain pan at
least once each year. The coils are easily cleaned when dry;
therefore, inspect and clean the coils either before or after each
cooling season. Remove all obstructions, including weeds and
shrubs, that interfere with the airflow through the condenser coil.
Straighten bent fins with a fin comb. If coated with dirt or lint,
clean the coils with a vacuum cleaner, using the soft brush
attachment. Be careful not to bend the fins. If coated with oil or
grease, clean the coils with a mild detergent--and--water solution.
Rinse coils with clear water, using a garden hose. Be careful not to
splash water on motors, insulation, wiring, or air filter(s). For best
results, spray outdoor coil fins from inside to outside the unit. On
units with an outer and inner condenser coil, be sure to clean
between the coils. Be sure to flush all dirt and debris from the unit
base.
Inspect the drain pan and condensate drain line when inspecting
the coils. Clean the drain pan and condensate drain by removing all
foreign matter from the pan. Flush the pan and drain tube with
clear water. Do not splash water on the insulation, motor, wiring, or
air filter(s). If the drain tube is restricted, clear it with a “plumbers
snake” or similar probe device. Ensure that the auxiliary drain port
above the drain tube is also clear.

Outdoor Fan

BLOWER
HOUSING

CAUTION

UNIT OPERATION HAZARD

Keep the outdoor fan free from all obstructions to ensure
proper cooling operation. Never place articles on top of the
unit.
1. Remove 6 screws holding outdoor grille and motor to top
cover.
2. Turn motor/grille assembly upside down on top cover to
expose the fan blade.
3. Inspect the fan blades for cracks or bends.
4. If fan needs to be removed, loosen the setscrew and slide the
fan off the motor shaft.
5. When replacing fan blade, position blade back to the same
position as before.
6. Ensure that setscrew engages the flat area on the motor shaft
when tightening.
7. Replace grille.

2 SETSCREWS
(HIDDEN)

C99085

Fig. 20 -- Removal of Motor and Blower Wheel

Electrical Controls and Wiring

A07680

Fig. 21 -- Burner Rack Removed
FEEDER TUBE
STUB TUBE

Inspect and check the electrical controls and wiring annually. Be
sure to turn off the gas supply, and then the electrical power to the
unit.
Remove access panels (see Fig. 19) to locate all the electrical
controls and wiring. Check all electrical connections for tightness.
Tighten all screw connections. If any discolored or burned
connections are noticed, disassemble the connection, clean all the
parts, re--strip the wire end and reassemble the connection properly
and securely.
After inspecting the electrical controls and wiring, replace the
access panels (see Fig. 19). Start the unit, and observe at least one
complete heating cycle and one complete cooling cycle to ensure
proper operation. If discrepancies are observed in any operating
cycle, or if a suspected malfunction has occurred, check each
electrical component with the proper electrical instrumentation.
Refer to the unit wiring label when making these checkouts.
NOTE: Refer to the heating and/or cooling sequence of operation
in this publication as an aid in determining proper control
operation.

Refrigerant Circuit
Annually inspect all refrigerant tubing connections and the unit
base for oil accumulations. Detecting oil generally indicates a
refrigerant leak.

!
DEFROST
THERMOSTAT

WARNING

EXPLOSION,
PERSONAL
ENVIRONMENTAL HAZARD

C99029

INJURY

AND

Failure to follow this warning could result in personal injury,
death or property damage.

Fig. 22 -- Defrost Thermostat Location

System under pressure. Relieve pressure and recover all
refrigerant before system repair or final unit disposal. Use all
service ports and open all flow--control devices, including
solenoid valves.
If oil is detected or if low cooling performance is suspected,
leak--test all refrigerant tubing using an electronic leak--detector,
halide torch, or liquid--soap solution. If a refrigerant leak is
detected, refer to the Check for Refrigerant Leaks section.

48VT-- A

Failure to follow this caution may result in damage to unit
components.

If no refrigerant leaks are found and low cooling performance is
suspected, refer to the Checking and Adjusting Refrigerant Charge
section.

switches are specifically designed to operate with Puron (R--410A)
systems. R--22 pressure switches must not be used as replacements
for the Puron (R--410A) system.

Gas Input

Loss of Charge Switch

The gas input does not require checking unless improper heating
performance is suspected. If a problem exists, refer to the Start--Up
section.

This switch is located on the liquid line and protects against low
suction pressures caused by such events as loss of charge, low
airflow across indoor coil, dirty filters, etc. It opens on a pressure
drop at about 20 psig. If system pressure is above this, switch
should be closed. To check switch:
1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohm meter leads across switch. You should have
continuity on a good switch.
NOTE: Because these switches are attached to refrigeration
system under pressure, it is not advisable to remove this device for
troubleshooting unless you are reasonably certain that a problem
exists. If switch must be removed, remove and recover all system
charge so that pressure gauges read 0 psi. Never open system
without breaking vacuum with dry nitrogen.
High--Pressure Switch
The high--pressure switch is located in the discharge line and
protects against excessive condenser coil pressure. It opens at 650
psig.
High pressure may be caused by a dirty outdoor coil, failed fan
motor, or outdoor air recirculation. To check switch:
1. Turn off all power to unit.
2. Disconnect leads on switch.
3. Apply ohm meter leads across switch. You should have
continuity on a good switch.

Indoor Airflow
The heating and/or cooling airflow does not require checking
unless improper performance is suspected. If a problem exists, be
sure that all supply-- and return--air grilles are open and free from
obstructions, and that the air filter is clean. When necessary, refer to
the Indoor Airflow and Airflow Adjustments section to check the
system airflow.

Check Defrost Thermostat

48VT-- A

The defrost thermostat is usually located on the lowest liquid
leaving circuit of the left condenser coil (see Fig. 22). The
thermostat closes at 32_F (0_C) and opens at 65_F (18_C).

Puron Items
Metering Device (Thermostatic Expansion Valve &
Piston)
This unit uses both a hard shutoff, balance port TXV in the indoor
coil and a piston in each side of the outdoor coil. The TXV
maintains a constant superheat at the evaporator coil exit (cooling
mode) resulting in higher overall system efficiency.

Pressure Switches
Pressure switches are protective devices wired into control circuit
(low voltage). They shut off compressor if abnormally high or low
pressures are present in the refrigeration circuit. These pressure

OF1

DFT

OF2

T2 C C O
T1

O R W2 Y C

Y
30

120

DFT

QUIET
SHIFT

90
INTERVAL TIMER OFF

48VT-- A

SPEEDUP

Speedup
Pins

Quiet
Shift

Defrost interval
DIP switches
A08020

Fig. 23 -- Defrost Control
Copeland Scroll Compressor (Puron Refrigerant)
The compressor used in this product is specifically designed to
operate with Puron (R--410A) refrigerant and cannot be
interchanged.
The compressor is an electrical (as well as mechanical) device.
Exercise extreme caution when working near compressors. Power
should be shut off, if possible, for most troubleshooting techniques.
Refrigerants present additional safety hazards.

WARNING

The scroll compressor pumps refrigerant throughout the system by
the interaction of a stationary and an orbiting scroll. The scroll
compressor has no dynamic suction or discharge valves, and it is
more tolerant of stresses caused by debris, liquid slugging, and
flooded starts. The compressor is equipped with an internal
pressure relief port. The pressure relief port is a safety device,
designed to protect against extreme high pressure. The relief port
has an operating range between 550 and 625 psi differential
pressure.

EXPLOSION HAZARD
Failure to follow this warning could result in personal injury
or death and/or property damage.
Wear safety glasses and gloves when handling refrigerants.
Keep torches and other ignition sources away from
refrigerants and oils.

48VT-- A

C99097

Fig. 24 -- Refrigerant Circuit

INDOOR COIL

OUTDOOR COIL

LCS
COMPRESSOR

ACCUMULATOR

TXV in Metering
Position

HP S

Bypass
Position

LEGEND
HPS – High Pressure Switch
LCS – Loss of Charge Switch
Accurater®Metering De vice
Arrow indicates direction of flo w

C03011

Fig. 25 -- Typical Heat Pump Operation, Cooling Mode

INDOOR COIL

OUTDOOR COIL

ACCUMULATOR

TXV in Bypass
Position

COMPRESSOR

LCS
HP S

Metering
Position

48VT-- A

LEGEND
HPS – High Pressure Switch
LCS – Loss of Charge Switch
Accurater®Metering De vice
Arrow indicates direction of flo w

C03012

Fig. 26 -- Typical Heat Pump Operation, Heating Mode

WARNING

UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could result in personal injury
or equipment damage.
This system uses Puron (R--410A) refrigerant which has
higher operating pressures than R--22 and other refrigerants.
No other refrigerant may be used in this system. Gauge set,
hoses, and recovery system must be designed to handle Puron.
If you are unsure, consult the equipment manufacturer.
Refrigerant System
This information covers the refrigerant system of the 48VT--A
including the compressor oil needed, servicing systems on roofs
containing synthetic materials, the filter drier and refrigerant
charging.
Compressor Oil
If additional oil is needed use Uniqema RL32--3MAF. If this oil is
not available, use Copeland Ultra 32CC or Mobil Artic EAL22CC.
This oil is extremely hygroscopic, meaning it absorbs water
readily. POE oils can absorb 15 times as much water as other oils
designed for HCFC and CFC refrigerants. Take all necessary
precautions to avoid exposure of the oil to the atmosphere.
Servicing Systems on Roofs and with Synthetic materials
POE (polyolester) compressor lubricants are known to cause long
term damage to some synthetic roofing materials.
Exposure, even if immediately cleaned up, may cause
embrittlement (leading to cracking) to occur in one year or more.
When performing any service that may risk exposure of
compressor oil to the roof, take appropriate precautions to protect
roofing. Procedures which risk oil leakage include, but are not
limited to, compressor replacement, repairing refrigerant leaks,
replacing refrigerant components such as filter drier, pressure
switch, metering device, coil, accumulator, or reversing valve.

Synthetic Roof Precautionary Procedure
1. Cover extended roof working area with an impermeable
polyethylene (plastic) drip cloth or tarp. Cover an
approximate 10x10 ft (3x3 m) area.
2. Cover area in front of the unit service panel with a terry
cloth shop towel to absorb lubricant spills and prevent
run--offs, and protect drop cloth from tears caused by tools
or components.
3. Place terry cloth shop towel inside unit immediately under
component(s) to be serviced and prevent lubricant run--offs
through the louvered openings in the unit base.
4. Perform required service.
5. Remove and dispose of any oil contaminated material per
local codes.
Liquid Line Filter Drier
This filter drier is specifically designed to operate with Puron. Use
only factory--authorized components. Filter drier must be replaced
whenever the refrigerant system is opened. When removing a filter
drier, use a tubing cutter to cut the drier from the system. Do not
unsweat a filter drier from the system. Heat from unsweating will
release moisture and contaminants from drier into system.
Puron (R--410A) Refrigerant Charging
Refer to unit information plate and charging chart. Some R--410A
refrigerant cylinders contain a dip tube to allow liquid refrigerant to
flow from cylinder in upright position. For cylinders equipped
with a dip tube, charge Puron units with cylinder in upright
position and a commercial metering device in manifold hose.
Charge refrigerant into suction--line.

TROUBLESHOOTING
Use the Troubleshooting Guides (See Tables 10--12) if problems
occur with these units.

START--UP CHECKLIST
Use Start--Up checklist to ensure proper start--up procedures are
followed.

PURONR (R--410A) QUICK REFERENCE GUIDE
Puron refrigerant operates at 50--70 percent higher pressures than R--22. Be sure that servicing equipment and replacement
components are designed to operate with Puron
S Puron refrigerant cylinders are rose colored.
S

S
S

Recovery cylinder service pressure rating must be 400 psig, DOT 4BA400 or DOT BW400.
Puron systems should be charged with liquid refrigerant. Use a commercial type metering device in the manifold hose when

48VT-- A

charging into suction line with compressor operating
S

Manifold sets should be minimum 700 psig high side and 180 psig low side with 550 psig low--side retard.

Use hoses with minimum 700 psig service pressure rating.

Leak detectors should be designed to detect HFC refrigerant.

Puron, as with other HFCs, is only compatible with POE oils.

Vacuum pumps will not remove moisture from oil.

Do not use liquid--line filter driers with rated working pressures less than 600 psig.

Do not leave Puron suction line filter driers in line longer than 72 hrs.

Do not install a suction--line filter drier in liquid line.

POE oils absorb moisture rapidly. Do not expose oil to atmosphere.

POE oils may cause damage to certain plastics and roofing materials.

Wrap all filter driers and service valves with wet cloth when brazing.

A factory approved liquid--line filter drier is required on every unit.

Do NOT use an R--22 TXV.

Never open system to atmosphere while it is under a vacuum.

When system must be opened for service, recover refrigerant, evacuate then break vacuum with dry nitrogen and replace filter
driers. Evacuate to 500 microns prior to recharging.

Do not vent Puron into the atmosphere.

Observe all warnings, cautions, and bold text.

All indoor coils must be installed with a hard shutoff Puron TXV metering device.

Table 11 – Troubleshooting Guide -- Cooling or Heat Pump Heating Mode

Compressor and Outdoor fan will not
start.

Compressor will not start but Outdoor
fan runs.

CAUSE
Power Failure
Fuse blown or circuit breaker tripped
Defective thermostat, contactor, transformer, or control
relay
Insufficient line voltage
Incorrect or faulty wiring
Thermostat setting too high
Faulty wiring or loose connections in compressor circuit
Compressor motor burned out, seized, or internal overload open
Defective run/start capacitor, overload, start relay
One leg of 3 ---phase power dead

Three --- phase scroll compressor makes
excessive noise, and there may
be a low pressure differential.

Scroll compressor is rotating in the wrong direction
Refrigerant overcharge or undercharge

Compressor cycles (other than normally
satisfying thermostat).

Compressor operates continuously.

Defective compressor
Insufficient line voltage
Blocked Outdoor
Defective run/start capacitor, overload or start relay
Defective thermostat
Faulty Outdoor ---fan motor or capacitor
Damaged reversing valve
Restriction in refrigerant system
Dirty air filter
Unit undersized for load
Thermostat set too low
Low refrigerant charge
Mechanical damage in compressor.
Air in system
Frosted coil with incorrect defrost operation

Excessive head pressure.

Head pressure too low.

Excessive suction pressure.

Suction pressure too low.

Outdoor coil dirty or restricted
Dirty air filter
Dirty Indoor or Outdoor coil
Refrigerant overcharged
Air in system
Indoor or Outdoor air restricted or air short---cycling
Low refrigerant charge
Compressor IPR leaking
Restriction in liquid tube
High heat load
Compressor IPR leaking
Refrigerant overcharged
Reversing valve hung up or leaking internally
Dirty air filter
Low refrigerant charge
Metering device or low side restricted
Insufficient Indoor airflow
Temperature too low in conditioned area
Outdoor ambient below 55°F (12.8°C)
Field---installed filter ---drier restricted
(Heat) Outdoor coil frosted

Compressor runs but outdoor fan does
not

NC (normally closed) contacts on defrost board open

REMEDY
Call power company.
Replace fuse or reset circuit breaker.
Replace component.
Determine cause and correct.
Check wiring diagram and rewire correctly.
Lower thermostat setting below room temperature.
Check wiring and repair or replace.
Determine cause Replace compressor.
Determine cause and replace.
Replace fuse or reset circuit breaker. Determine
cause.
Correct the direction of rotation by reversing the
3 ---phase power leads to the unit.
Recover refrigerant, evacuate system, and recharge
to capacities shown on nameplate.
Replace and determine cause.
Determine cause and correct.
Determine cause and correct.
Determine cause and replace.
Replace thermostat.
Replace.
Determine cause and correct
Locate restriction and remove.
Replace filter.
Decrease load or increase unit size.
Reset thermostat.
Locate leak, repair, and recharge.
Replace compressor.
Recover refrigerant, evacuate system, and recharge.
Check defrost time settings, Reset as necessary
Check defrost temperature switch, Replace as necessary
Clean coil or remove restriction .
Replace filter.
Clean coil.
Recover excess refrigerant.
Recover refrigerant, evacuate system, and recharge.
Determine cause and correct.
Check for leaks, repair, and recharge.
Replace compressor.
Remove restriction.
Check for source and eliminate.
Replace compressor.
Recover excess refrigerant.
Replace valve
Replace Filter.
Check for leaks, repair, and recharge.
Remove source of restriction.
Increase air quantity. Check filter — replace if necessary.
Reset thermostat.
Install low---ambient kit.
Replace.
Move timer on control board to 30 minutes between
defrost cycles
Check condition of relay on board Replace if necessary

48VT-- A

SYMPTOM

Table 12 – Troubleshooting Guide–Heating
SYMPTOM

CAUSE
Water in gas line
No power to furnace
No 24--v power supply to control circuit

Burners will not ignite

Mis--wired or loose connections
Misaligned spark electrodes

No gas at main burners

Inadequate heating

Dirty air filter
Gas input to furnace too low
Unit undersized for application
Restricted airflow

48VT-- A

Limit switch cycles main burners

Poor flame characteristics

Incomplete combustion results in: Aldehyde odors,
carbon monoxide, sooting flame, floating flame

REMEDY
Drain. Install drip leg.
Check power supply fuses, wiring or circuit breaker.
Check transformer.
NOTE: Some transformers have internal over--current protection
that requires a cool--down period to reset.
Check all wiring and wire nut connections
Check flame ignition and sense electrode positioning.
Adjust as necessary.
1. Check gas line for air. Purge as necessary. NOTE: After purging
gas line of air, wait at least 5 minutes for any gas to dissipate before attempting to light unit.
2. Check gas valve.
Clean or replace filter as necessary
Check gas pressure at manifold match with that on unit nameplate
Replace with proper unit or add additional unit
Clean or replace filter. Remove any restriction.
Check rotation of blower, temperature rise of unit. Adjust as necessary.
1. Tighten all screws around burner compartment
2. Cracked heat exchanger. Replace.
3. Unit over--fired. Reduce input (change orifices or adjust gas line
or manifold pressure).
4. Check burner alignment.
5. Inspect heat exchanger for blockage. Clean as necessary.

Table 13 – Troubleshooting Guide–LED Status Codes
SYMPTOM

CAUSE

REMEDY
Check 5--amp fuse son IGC*, power to unit, 24--v circuit breaker,
and transformer. Units without a 24--v circuit breaker have an
internal overload in the 24--v transformer. If the overload trips,
allow 10 minutes for automatic reset.

No Power Hardware failure
(LED OFF)

Loss of power to control module (IGC)*.

Limit switch faults
(LED 2 flashes)

High temperature limit switch is open.

Check the operation of the indoor (evaporator) fan motor. Ensure
that the supply--air temperature rise is in accordance with the
range on the unit nameplate. Clean or replace filters.

The IGC* sensed flame that should not be present.

Reset unit. If problem persists, replace control board.

Flame sense fault
(LED 3 flashes)
4 consecutive limit switch
faults
(LED 4 flashes)

Inadequate airflow to unit.

Ignition lockout
(LED 5 flashes)

Unit unsuccessfully attempted ignition for 15 minutes.

Pressure Switch motor fault
(LED 6 flashes)

Open pressure switch.

Rollout switch fault
(LED 7 flashes)

Rollout switch has opened.

Internal control fault
(LED 8 flashes)
Temporary 1 hr auto reset
(LED 9 flashes)

Microprocessor has sensed an error in the software
or hardware.
Electrical interference impeding IGC software

Check the operation of the indoor (evaporator) fan motor and that
supply--air temperature rise agrees with range on unit nameplate
information.
Check ignitor and flame sensor electrode spacing, gaps, etc.
Ensure that fame sense and ignition wires are properly terminated.
Verify that unit is obtaining proper amount of gas.
Verify wiring connections to pressure switch and inducer motor.
Verify pressure switch hose is tightly connected to both inducer
housing and pressure switch. Verify inducer wheel is properly
attached to inducer motor shaft. Verify inducer motor shaft is turning.
Rollout switch will automatically reset, but IGC* will continue to
lockout unit. Check gas valve operation. Ensure that induced--draft
blower wheel is properly secured to motor shaft. Inspect heat
exchanger. Reset unit at unit disconnect.
If error code is not cleared by resetting unit power, replace the
IGC*.
Reset 24--v. to control board or turn thermostat off, then on again.
Fault will automatically reset itself in one (1) hour.

*WARNING
: If the IGC must be replaced, be sure to ground yourself to dissipate any electrical charge that my be present before handling new control
board. The IGC is sensitive to static electricity and my be damaged if the necessary precautions are not taken.
IMPORTANT: Refer to Table 12 ---Troubleshooting Guide ---Heating for additional troubleshooting analysis.
LEGEND
IGC—Integrated Gas Unit Controller
LED—Light---Emitting Diode

START--UP CHECKLIST
(Remove and Store in Job Files)
I. PRELIMINARY INFORMATION
MODEL NO.:
SERIAL NO.:
DATE:
TECHNICIAN:

III. START--UP
ELECTRICAL
SUPPLY VOLTAGE
COMPRESSOR AMPS
INDOOR (EVAPORATOR) FAN AMPS
TEMPERATURES
OUTDOOR (CONDENSER) AIR TEMPERATURE
DB
RETURN--AIR TEMPERATURE
DB
WB
COOLING SUPPLY AIR
DB
WB
HEAT PUMP SUPPLY AIR__________________
GAS HEAT SUPPLY AIR
PRESSURES
GAS INLET PRESSURE
IN. W.C.
GAS MANIFOLD PRESSURE
IN. W.C.
REFRIGERANT SUCTION
PSIG, SUCTION LINE TEMP*
REFRIGERANT DISCHARGE
PSIG, LIQUID TEMP{
( ) VERIFY REFRIGERANT CHARGE USING CHARGING CHARTS
GAS HEAT TEMPERATURE RISE
TEMPERATURE RISE (See Literature) RANGE
MEASURED TEMPERATURE RISE
* Measured at suction inlet to compressor
{ Measured at liquid line leaving condenser.

48VT-- A

II. PRESTART--UP (Insert check mark in box as each item is completed)
( ) VERIFY THAT ALL PACKING MATERIALS HAVE BEEN REMOVED FROM UNIT
( ) REMOVE ALL SHIPPING HOLD DOWN BOLTS AND BRACKETS PER INSTALLATION INSTRUCTIONS
( ) CHECK ALL ELECTRICAL CONNECTIONS AND TERMINALS FOR TIGHTNESS
( ) CHECK GAS PIPING FOR LEAKS (WHERE APPLICABLE)
( ) CHECK THAT INDOOR (EVAPORATOR) AIR FILTER IS CLEAN AND IN PLACE
( ) VERIFY THAT UNIT INSTALLATION IS LEVEL
( ) CHECK FAN WHEEL, AND PROPELLER FOR LOCATION IN HOUSING/ORIFICE AND SETSCREW TIGHTNESS

48VT-- A
Copyright 2009 Carrier Corp. S 7310 W. Morris St. S Indianapolis, IN 46231

Edition Date: 04/09

Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.

Catalog No: 48VT ---05SI
Replaces: 48VT--- 04SI

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Carrier 48Vtn Users Manual 48VT 05SI

48VT(N) 48VT-05SI

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