Honeywell Aquastat L8124C Users Manual 95 6571 L8124A,C,E,L And M Aquastat® Relays

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Copyright © 2001 Honeywell • All Rights Reserved

INSTALLATION INSTRUCTIONS

95- 6571- 11

L8124A,C,E,L and M

Aquastat® Relays

APPLICATION

These immersion type controllers are used with forced

hydronic heating systems that include domestic hot water

service. All models provide high limit, low limit and

circulator control. Table 1 lists the various models and

their applications.

These Aquastat® relays have a diaphragm powerhead

and MicroSwitch™ assembly that respond to

temperature changes in the boiler water. L8124 can

provide multizone control by using a separate circulator

and R845 Relay for each zone. L8124E and L have large

transformers and extra terminals for supplying power to

low voltage valves. L8124L includes a large transformer

and extra terminals for low voltage zone valves. L8124M

is for use in a wood-coal/gas-oil multifuel heating system.

Circulator is independently controlled by the thermostat.

Do not use these Aquastat® Relays where the pressure

can exceed 100 psi (690 kPa) on the bulb if inserted

directly or 200 psi (1380 kPa) when using an immersion

well, or where the ambient temperature can exceed

150°F (66°C) at the case or 265°F (129°C) at the sensing

element.

SPECIFICATIONS

Low Limit:

Setting: 110°F to 220°F (43°C to 104°C), adjustable.

Differential: 10°F to 25°F (6°C to 14°C), adjustable.

High Limit:

Setting: 130°F to 240°F (54°C to 116°C), adjustable.

Differential: 10°F (6°C), fixed.

WARNING

Explosion Hazard.

Can cause serious injury, death or property

damage.

Use this product only in systems with a pressure

relief valve.

Table 1. Model Descriptions.

a Multizone control can be provided by using a separate circulator and R845 Relay for each zone.

Model

Number

Burner

Control

Circuit

Can Be Used For

Multizone With

Circulatorsa

No. of V8043 Zone

Valves Powered

Without Additional

Transformer

Electrical Ratings

Burner Circuit Circulator Circuit

L8124A 120V Yes — Same as L8124A,C,L

circulator rating.

120 Vac: 7.4A (full load),

44.4A (locked rotor).

240 Vac: 3.7A (full load),

22.2A (locked rotor).

L8124C

L8124L 3

L8124E 24V 2 1.25A at 24 Vac; 30 VA

(total load) B1-B2, Tv-Z.

L8124M 120V — Same as L8124A. None.

L8124A,C,E,L AND M AQUASTAT® RELAYS

95-6571—11 2

INSTALLATION

When Installing This Product…

1. Read these instructions carefully. Failure to follow

them could damage the product or cause a

hazardous condition.

2. Check the ratings given in the instructions and on

the product to make sure the product is suitable for

your application.

3. Installer must be a trained, experienced service

technician.

4. After installation is complete, check out product

operation as provided in these instructions.

WARNING

Electrical Shock Hazard.

Can cause severe injury, death or equipment

damage.

Disconnect power supply before beginning

installation to prevent electrical shock or

equipment damage.

IMPORTANT

1. Terminals on these Aquastat Relays are

approved for copper wire only.

2. Immersion well must fit sensing element and

bulb must rest against bottom of well.

Bend the tubing, if necessary, to hold the bulb against the

bottom of the well. Do not make a sharp bend in the

tubing. A sharp bend can produce a break in the tubing

and cause loss of fill. This condition will cause the high

and low limit controllers to be continuously made.

Select models have an adjustable capillary length.

See Fig. 1.

Fig. 1. Adjusting the capillary length.

Mounting

Each relay is suitable for use with an immersion well for

insertion into the boiler. (Check individual OS number

specifications to determine whether a well is supplied

with the relay.) Refer to form 68-0040, Wells and Fittings

for Temperature Controllers, to order well. A compression

fitting is available for applications where direct immersion

of the sensing bulb is desired. A 124904 Well Adapter

(see Fig. 2) can be ordered separately to adapt some

other wells to the mounting clamp. The boiler must be

provided with a tapping that allows horizontal mounting of

the well. It should be located where boiler water of

average temperature can circulate around the well.

1. Turn off all power and drain the boiler.

2. If no tapping is provided, prepare one, properly

sized and threaded, at the selected location.

3. Install the immersion well in the boiler tapping and

tighten securely.

NOTE: Do not use the case as a handle to tighten.

4. Refill boiler and check for water leakage.

5. Loosen but do not remove the clamp screw on

the bottom (L8124A,E) or on top (L8124C,L,M)

of case.

6. Insert the element in the well until it bottoms.

See Fig. 2.

7. Fit the case onto the well so that the clamp on the

case slides over the flange on the well. Securely

tighten clamp screw.

WIRING

WARNING

Electrical Shock Hazard.

Can cause severe injury, death or equipment

damage.

Disconnect power before wiring to prevent

electrical shock or equipment damage.

All wiring must comply with local electrical codes and

ordinances. The limits given in the Specifications section

must not be exceeded when applying this control.

Terminals on these Aquastat Relays are approved for

copper wire only.

Refer to the insert on the inside of the Aquastat Relay

cover or to Table 1 for electrical ratings and maximum

load information. Use manufacturer instructions when

wiring controlled equipment or refer to typical hookups in

Fig. 3 through 11.

WARNING

Explosion Hazard.

Can cause severe injury, death or property

damage.

Use this product only in systems with a pressure

relief valve.

If the B1 terminal on the device being replaced is a 1/4 in.

(6 mm) tab terminal, use the existing wiring harness

terminals to install the replacement device. If the B1

terminal on the device being replaced is a screw

terminal, insert the provided tab terminal to screw

terminal adapter on the 1/4 in. (6 mm) tab terminal of the

replacement device. After the adapter is installed, the

existing wraparound wire end may be reused to make an

electrical connection to the B1 terminal.

M8882

SENSING ELEMENT IS FACTORY FORMED FOR 1.5 IN.

INSULATION WELL ASSEMBLIES.

FOR 3 IN. INSULATION WELL ASSEMBLIES, PULL OUT

SUFFICIENT CAPILLARY TO ASSURE THAT THE CAPSULE

BOTTOMS IN THE WELL.

STRAIGHTEN CAPILLARY SUFFICIENTLY SO IT DOES NOT

INTERFERE WITH INSERTION OF THE CAPSULE INTO THE WELL.

CAUTION:

EXCESSIVE HANDLING OR SHARP BENDS

CAN DAMAGE THE CAPILLARY.

1

2

3

12

3

L8124A,C,E,L AND M AQUASTAT® RELAYS

3 95-6571—11

Fig. 2. Position of bulb in immersion well and use of well adapter when required.

Fig. 3. L8124A,C single zone connections

and internal schematic.

Fig. 4. L8124E single zone connections

and internal schematic.

CONTROLLER

CASE

IMMERSION

WELL CLAMP

ADAPTER

IMMERSION

WELL SPUD

BOILER

OLD IMMERSION

WELL ASSEMBLY

BACK

OF

CONTROLLER

CASE

IMMERSION

WELL CLAMP

SCREW

ADAPTER

SENSING

BULB

HEAT-CONDUCTIVE COMPOUND

SETSCREW

CAPILLARY

TUBE

)

IMMERSION

WELL CLAMP

IMMERSION

WELL CLAMP SCREW

SHORT TUBE

FITS IN CENTRAL

RECESS OF ADAPTER

BEND THE CAPILLARY TUBE TO HOLD THE SENSING BULB IN GOOD

THERMAL CONTACT WITH THE IMMERSION WELL AT POINTS (A) AND (B).

ASSURE THAT CAPILLARY TUBE FITS FREELY IN THE ADAPTER SO THE

TENSION OF THE CAPILLARY TUBE AT POINT (C) HOLDS THE SENSING

BULB IN GOOD THERMAL CONTACT WITH THE IMMERSION WELL AT POINT (

D

M883

1

1

2

2

(D)

(B)

(A)

M8802

L1

(HOT)

L2 1

1

2

2

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.

USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

LINE VOLTAGE

OIL BURNER

RELAY OR

GAS VALVE

LINE VOLTAGE

CIRCULATOR

C2

C1

B2

B1

R

B

HIGH

LIMIT

ZC

ZR

1K1

B

R

W

LOW LIMIT/

CIRCULATOR

1K

2

1

G

T

T

L8124A,C

LOW VOLTAGE

THERMOSTAT

1K2 3

3

M8803

L1

(HOT)

L2 1

3

1

2

3

2

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.

USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

LOW VOLTAGE

GAS VALVE

(eg, VR8300)

LINE VOLTAGE

CIRCULATOR

C2

C1

B2

B1

R

B

HIGH

LIMIT

Z

1K1

B

R

W

LOW LIMIT/

CIRCULATOR

1K 2

1

G

T

TV

L8124E

LOW VOLTAGE

THERMOSTAT

1K2

TR

TH

L8124A,C,E,L AND M AQUASTAT® RELAYS

95-6571—11 4

Fig. 5. L8124A in an oil-fired, forced hot water, tankless, zoned, pump system.

Fig. 6. L8124A,C multizone system with circulator connections and internal schematic.

L1

(HOT)

L2

1

23

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

TT

L2 L1 C1 C2 B2

ZR

ZC

B1

M8822

3

2

BURNER

AND

IGNITION

L8124A

G

T

T

F

F

T87F

TT

123456

T87F

R845 RELAY

R8184

TT

123456

T87F

R845 RELAY

PUMP PUMP PUMP

BLACK

WHITE

ORANGE

C554

1

M8827

L1

(HOT)

L2

1

1

2

3

2

3

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH

GROUND. USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

LINE VOLTAGE

OIL BURNER

RELAY OR

GAS VALVE

LINE VOLTAGE

CIRCULATOR

C2

C1

B2

B1

R

B

HIGH

LIMIT

ZC

ZR

1K1

B

R

W

LOW LIMIT/

CIRCULATOR

1K

2

2

1

4

3

5

6

1

G

T

T

L8124A,C

LOW VOLTAGE

THERMOSTAT

1K2 ZONE 2

LOW VOLTAGE

THERMOSTAT

R845A RELAY ZONE 2

ZONE 2

CIRCULATOR

TO ADDITIONAL

R845A RELAYS

FOR OTHER ZONES

L8124A,C,E,L AND M AQUASTAT® RELAYS

5 95-6571—11

Fig. 7. L8124 multizone system with zone valve

connections and internal schematic.

Fig. 8. L8124E in a 24Vac, gas-fired,

forced hot water, tankless system.

M1795B

L1

(HOT)

L2 1

1

2

3

4

3

2

4

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

UP TO TWO V8043F ZONE VALVES CAN BE POWERED WITH

L8124G,L. ADD ADDITIONAL TRANSFORMER FOR EVERY

TWO OR LESS VALVES.

CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.

USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

LINE VOLTAGE

OIL BURNER

RELAY OR

GAS VALVE

LINE VOLTAGE

CIRCULATOR

B2

C2

C1

ZR

B1R

B

HIGH

LIMIT

Z

1K1

B

R

W

LOW LIMIT/

CIRCULATOR

1K

2

1

G

T

TV

L8124G,L

ZONE 1

THERMOSTAT

1K2

V8043F

TH

TR TH TR

ZONE 2

THERMOSTAT

V8043F

TH

TR TH TR

ZC

L1

(HOT)

L2

1

2

3

2

3

1

TH TR

LOW VOLTAGE

GAS VALVE

(eg, VR8300)

L8124E

GL2 L1

C1 C2

TT

B2 B1

T87F

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.

USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

CIRCULATOR

M1796A

L8124A,C,E,L AND M AQUASTAT® RELAYS

95-6571—11 6

Fig. 9. L8124E in a 24 Vac, gas-fired, forced hot water, tankless, zoned pump system.

Fig. 10. L8124E multizone system with circulator connections and internal schematic.

L1

(HOT)

L2

1

2

3

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

TT

123456

M1794A

TH

1

2

3

TR

LOW VOLTAGE

GAS VALVE

(eg, VR8300)

L8124E

AQUASTAT® RELAY

GL2 L1

C1 C2

TT

B2 B1

T87F

R845 RELAY

TT

123456

T87F

R845 RELAY

TT

123456

T87F

R845 RELAY

PUMP PUMP PUMP

M8828

L1

(HOT)

L2

1

1

2

3

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH

GROUND. USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

2

1

4

3

5

6

ZONE 1

LOW VOLTAGE

THERMOSTAT

R845A RELAY ZONE 1

ZONE 1

CIRCULATOR

TO ADDITIONAL

R845A RELAYS

FOR OTHER ZONES

2

3

LOW VOLTAGE

GAS VALVE (eg, VR8300)

C2

C1

B2

B1

R

B

HIGH

LIMIT

Z

1K1

B

R

W

LOW LIMIT/

CIRCULATOR

1K 2

1

G

T

TV

L8124E

1K2

TR

TH

THTR

L8124A,C,E,L AND M AQUASTAT® RELAYS

7 95-6571—11

Fig. 11. L8124L multizone system with circulator connections and internal schematic.

OPERATION

High Limit Controller

The high limit opens and turns off the burner when the

water temperature reaches the setpoint. The high limit

automatically resets after the water temperature drops

past the setpoint and through the 10°F (6°C) differential.

WARNING

Explosion Hazard.

Can cause serious injury, death or equipment

damage.

Use this product only in systems with a pressure

relief valve.

Low Limit and Circulator Controllers

On a temperature rise, with the adjustable differential at

the minimum setting of 10°F (6°C), the burner circuit

(R-B) breaks and the circulator circuit (R-W) makes at

the control setpoint. On a temperature drop of 10°F (6°C)

below the setpoint, the R-B circuit makes and the R-W

circuit breaks. See Fig. 12.

At any differential setting greater than 10°F (6°C), the

R-B make temperature and the R-W break temperature

remain the same (control setting minus 10°F [6°C]). The

R-B break and R-W make temperature are the setpoint

temperature plus the difference between the differential

setting and 10°F (6°C).

EXAMPLE: Setpoint of 140°F (60°C), differential set

at 25°F (14°C). On a temperature rise, R-B breaks

and R-W makes at 155°F (68°C). On a temperature

fall, R-B makes and R-W breaks at 130°F (54°C).

Fig. 12. Relationship of setpoints and differential.

M8829

L1

(HOT)

L2

1

3

1

2

3

2

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH

GROUND. USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

2

1

4

3

5

6

LOW VOLTAGE

THERMOSTAT

ZONE 1

ZONE 2

LOW VOLTAGE

THERMOSTAT

R845A RELAY ZONE 2

ZONE 2

CIRCULATOR

TO ADDITIONAL

R845A RELAYS

FOR OTHER ZONES

LINE VOLTAGE

OIL BURNER

RELAY OR

GAS VALVE

LINE VOLTAGE

CIRCULATOR

ZONE 1

B2

C2

C1

ZR

B1R

B

HIGH

LIMIT

Z

1K1

B

R

W

LOW LIMIT/

CIRCULATOR

1K

2

1

G

T

TV

L8124L

1K2

ZC

LOW LIMIT

AND

CIRCULATOR

SETTING

HIGH LIMIT

SETTING

SWITCH BREAKS ON

TEMPERATURE RISE.

BURNER TURNS OFF.

CIRCULATOR OPERATES

ON A CALL FOR HEAT.

SWITCH MAKES ON

TEMPERATURE FALL.

BURNER OPERATES ON A

CALL FOR HEAT.

SWITCH MAKES R-W

AND BREAKS R-B ON

TEMPERATURE RISE.

SWITCH MAKES R-B AND

BREAKS R-W ON

TEMPERATURE FALL.

BURNER IS ON TO

MAINTAIN MINIMUM

WATER TEMPERATURE.

CIRCULATOR IS OFF.

M1523

SWITCH MAKES R-W

AND BREAKS R-B ON

TEMPERATURE RISE.

WHEN WATER REACHES PROPER TEMPERATURE, THE BURNER

SHUTS OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING

FOR HEAT).

1

1

95-6571—11 G.R. Rev. 12-01 www.honeywell.com

L8124A,C,E,L AND M AQUASTAT® RELAYS

Automation and Control SolutionsAutomation and Control Solutions

Honeywell Honeywell Limited-Honeywell Limitée

1985 Douglas Drive North 35 Dynamic Drive

Golden Valley, MN 55422 Scarborough, Ontario

M1V 4Z9

On the L8124M, the burner and circulator circuits are

separately controlled; the low limit controls the burner

circuit (R-B) as described above, while the low voltage

thermostat directly controls the circulator circuit.

See Fig. 13.

Fig. 13. L8124M single zone connections

and internal schematic.

SETTING

Follow the boiler manufacturer recommendations when

making the L8124 settings. The high limit setting must be

at least 20°F (11°C) higher than the low limit setting. Set

the indicators over the selected temperature marks. The

low limit differential is set by turning the differential

adjustment knob to the desired amount of differential.

The thermostat heat anticipator should be set at 2.0A.

CHECKOUT

Put the system into operation and observe each function

through at least one complete cycle. Be sure the control

operates as intended.

M8804

L1

(HOT)

L2 1

3

1

2

3

2

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

CONTROL CASE MUST BE CONNECTED TO EARTH

GROUND. USE GROUNDING SCREW PROVIDED.

B1 IS 1/4 IN. TAB TERMINAL.

LINE VOLTAGE

OIL BURNER

RELAY OR

GAS VALVE

LINE VOLTAGE

CIRCULATOR

C2

C1

B2

B1

R

B

HIGH

LIMIT

ZC

1K1

B

R

W

LOW LIMIT

1K

L2

L1

G

TT

L8124M

LOW VOLTAGE

THERMOSTAT