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INSTALLATION INSTRUCTIONS

69- 1232- 2

L7124U Universal Oil

Electronic Aquastat® Controller

APPLICATION

The L7124U Universal Oil Electronic Aquastat® 
Controller provides electronic temperature sensing in a 
UL limit-rated control with a single sensing probe. The 
L7124U controls circulator, oil burner and boiler 
temperature. The L7124U replaces the L8124A, L8124C 
and L8148A Controllers.

General

The L7124U Universal Oil Electronic Aquastat® 
Controller is a primary safety limit-rated device designed 
for use with oil fired boilers with line voltage burners and 
circulators. The boilers do not include wiring or control 
compartments as part of the design, but are provided 
with an integral, replaceable, immersion well that is the 
mounting hardware for the L7124U. Wiring to the other 
controls is done through flexible metal conduit. A 
separate electromechanical high-limit is not required in a 
system that uses this control.

A manually-adjusted potentiometer is used to set the 
High Limit. The overall range of the High Limit dial is from 
130°F to 240°F (54°C to 116°C). The High Limit is 
calibrated for accuracy at 212°F (100°C). Some models 
have limited ranges on the high limit setpoint; this limited 
range is listed on the device label, but the potentiometer 
travels the full mechanical distance.

Some models also have a Low Limit and Low Limit 
Differential adjustment. The range of the Low Limit dial is 
from 110°F to 220°F (43°C to 104°C). Rotating the Low 
Limit potentiometer fully counterclockwise disables 
the low limit function and turns on the Low Limit 
Disabled LED.

The L7124U is designed for use with 24 Vac electronic 
and electromechanical thermostats and has screw-type 
terminals for easy field connection. 

SPECIFICATIONS

Electrical Ratings:

Voltage: 120 Vac, 60 Hz.
Power: 10 VA maximum at 120 Vac plus external loads.
Thermostat current: 100 mA nominal at 24 Vac.
Burner Relay:

7.4A at 120 Vac Full Load Amperage (FLA);

44.4A inrush Locked Rotor Amperage (LRA);
Plus Ignition Load: 360 VA.

Circulator Relay:

7.4A at 120 Vac FLA; 44.4A inrush LRA.
Zone Controller (ZC): 7.4A at 120 Vac FLA; 

44.4A inrush LRA.

Differential Ratings:

High Limit Differential: 15°F subtractive.
Low Limit Differential: Adjustable 10°F to 25°F 

subtractive from Low Limit setpoint.

Environmental Ratings:

Temperature: -30°F to +150°F (-34°C to +66°C).
Humidity: 0 to 95% relative humidity, 
noncondensing.

Approvals:

Underwriters Laboratories Inc. Component Recognized: 

Pending approval.

Canadian Underwriters Laboratories Inc. Component 

Recognized: Pending approval.

Accessories

Accessories (Ordered Separately):

120650 Heat Conductive Compound
124904 Well Adapter
32002190-001 Relay
32004955-001 Sensor
4074GYZ Fuse, 1A (10-pack package)

Table 1. Wells for L7124U Controller.

Part 

Number

Spud Size 

(in.)

Insertion 

(in.)

Insulation 

(in.)

123869A

1/2 NPT

3

1-1/2

123870A

3/4 NPT

3

1-1/2

Summary of Contents for L7124U

Page 1: ... mechanical distance Some models also have a Low Limit and Low Limit Differential adjustment The range of the Low Limit dial is from 110 F to 220 F 43 C to 104 C Rotating the Low Limit potentiometer fully counterclockwise disables the low limit function and turns on the Low Limit Disabled LED The L7124U is designed for use with 24 Vac electronic and electromechanical thermostats and has screw type...

Page 2: ...e flange on the well 9 Securely tighten the clamp screw IMPORTANT Best thermal response is obtained with a well that snugly fits the sensor Insert the sensor until it rests against the bottom of the well use a well of correct length and bend the wiring if necessary to hold the bulb against the bottom of the well If the well is not a snug fit on the sensor use the heat conductive compound furnished...

Page 3: ...proved for use with copper wire only Follow the appropriate wiring diagrams shown on the inside of the front cover of the L7124U or in Fig 3 and 4 Fig 3 L7124U single zone connections SENSOR WIRES IMMERSION WELL CLAMP SCREW IMMERSION WELL CLAMP M16120 HEAT CONDUCTIVE COMPOUND OPTIONAL CONTROLLER CASE BOILER IMMERSION WELL SENSOR LOW LIMIT HIGH LIMIT DIFF SENSOR PWR T L2 T TSTAT DSBL LL B B2 B1 C2 ...

Page 4: ...CULATOR TO ADDITIONAL R845A RELAYS FOR OTHER ZONES LOW LIMIT HIGH LIMIT DIFF SENSOR PWR T L2 T TSTAT DSBL LL B B2 B1 C2 ZR ZC C1 C ZC 1 2 M17777 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 LINE VOLTAGE OIL BURNER RELAY LINE VOLTAGE CIRCULATOR LOW VOLTAGE THERMOSTAT T1 LEGEND LED SENSOR...

Page 5: ...he fixed differential 3 Low Limit Boiler temperature has gone below the low limit setting minus the low limit differential and has not gone above the low limit setting 4 Error The controller has detected an error condition e g open sensor and has shut down the burner output The circulator and ZC output are energized The controller continues to function and automatically restarts if the error condi...

Page 6: ...System Condition Check Corrective Action Boiler is cold house is cold PWR LED Off Check 120 Vac system power 1A fuse on L7124U PWR LED On TSTAT LED Off Check Thermostat Thermostat wiring PWR LED On TSTAT LED On B burner LED On Check 120 Vac B1 B2 If no replace burner relay If yes check burner and wiring PWR LED On TSTAT LED On LL DSBL LED Flashing Refer to LED diagnostics Table 3 Boiler is hot hou...

Page 7: ...7 69 1232 2 ...

Page 8: ... on recycled paper containing at least 10 post consumer paper fibers Home and Building Control Home and Building Control Honeywell Honeywell Limited Honeywell Limitée 1985 Douglas Drive North 35 Dynamic Drive Golden Valley MN 55422 Scarborough Ontario M1V 4Z9 ...

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