Honeywell L7124U Installation Instructions Manual

L7124U Universal Oil

Electronic Aquastat® Controller

INSTALLATION INSTRUCTIONS

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

123869A 1/2 NPT 3 1-1/2

123870A 3/4 NPT 3 1-1/2

Spud Size

(in.)

Insertion

(in.)

Insulation

(in.)

® U.S. Registered Trademark
Copyright © 2001 Honeywell • All Rights Reserved

69- 1232- 2

L7124U UNIVERSAL OIL ELECTRONIC AQUASTAT® CONTROLLER

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. The 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 serious injury or death.

Disconnect power supply before beginning
installation to prevent electrical shock or
equipment damage.

Mounting

The L7124U has a case that can be converted for either
horizontal or vertical mounting. See Fig. 1.

IMPORTANT

Immersion well must fit sensing element and
sensor bulb must rest against bottom of well.

New Installation

Order well assemblies for the L7124U separately; see
form 68-0040, Wells and Fittings for Temperature
Controllers. Boilers usually have tappings that allow
the well to be mounted horizontally so boiler water of
average temperature can circulate freely.

1. Turn off all power and drain the boiler.

2. If no tapping is provided, prepare properly sized

and threaded tapping near the top of the boiler.

3. Sparingly coat the well threads with pipe dope.

BRACKET POSITION FOR
VERTICAL MOUNTING

BRACKET POSITION FOR
HORIZONTAL MOUNTING

M8890

Fig. 1. Case designed for vertical

or horizontal mounting.

69-1232—2 2

NOTE: Do not attempt to tighten by using the case as a

handle.

4. Install the well in the boiler tapping and tighten
securely.

5. Refill boiler and check for water leakage.

6. Loosen but do not remove the clamp screw on the

L7124U case.

7. Insert the sensor element into the well until it
bottoms. (If necessary, slightly bend the tube inside
the case to hold the sensor against the bottom of
the well.)

NOTE: Some models have an adjustable wire length to

3 in. (76 mm). For these models, pull out extra
wire length from inside the case, if needed.

8. Fit the case into the well so the clamp on the case
slides over the 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 with
TRADELINE models) as follows: Fold the
plastic bag of compound lengthwise and twist it
gently. Then snip off end of bag and work the
open end of the bag all the way into the well.

Slowly pull out the bag while squeezing it firmly
to distribute compound evenly in the well. Bend
the wiring, if necessary, to hold the sensor
against the bottom of the well and to hold outer
end of the sensor in firm contact with the side of
the well. See Fig. 2. Wipe excess compound
from the outer end of the well.

Replacement Installation

Turn off all power and remove the old control. Refer
to the cover insert of the old control to identify and tag
each external lead as it is disconnected. If the old well is
unsuitable for the new installation, remove it and proceed
with instructions for new installation. If the old well is
suitable, use it and an immersion well adapter (ordered
separately) for the installation. (The well clamp may fit
directly over the flange of the existing well spud and
using the adapter may not be necessary.) The adapter
has a flange at the wide end that fits into the well clamp
and is slotted lengthwise to accommodate the sensor
wire.

1. Loosen but do not remove the well clamp screw on
the side of the control case.

2. Pull out the wire until the sensor bottoms in the
well. Place adapter, if used, around the sensor wire
so it fits into the slot. See Fig. 2.

3. Make sure the wide end of the adapter fits into the
hole in the case. Position immersion well clamp
snugly over the flange of the adapter and tighten
the clamp screw.

4. Insert the sensor into the well as shown in Fig. 2.
(Distribute the heat-conductive compound in the
tube prior to bulb insertion.)

5. Securely tighten the setscrew against the adapter.

L7124U UNIVERSAL OIL ELECTRONIC AQUASTAT® CONTROLLER

SENSOR WIRES

CONTROLLER CASE

IMMERSION
WELL CLAMP

IMMERSION WELL
CLAMP SCREW

BOILER

IMMERSION
WELL

HEAT-CONDUCTIVE COMPOUND
(OPTIONAL)

SENSOR

M16120

Fig. 2. Position of sensor in immersion well.

WIRING

WARNING

Electrical Shock Hazard.
Can cause serious injury or death.

Disconnect power supply before making wiring
connections to prevent electrical shock or
equipment damage.

All wiring must comply with local electrical codes and
ordinances. Do not exceed the specifications in the
Application section when wiring this control.

IMPORTANT

The terminals on these Aquastat® Controllers
are approved 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.

LINE VOLTAGE
CIRCULATOR

SENSOR

L2

L1
(HOT)

L1

T1

1

PWR

SENSOR

2
1

C

ZC

2

F01

LOW VOLTAGE
THERMOSTAT

TL2T TSTAT

HIGH
LIMIT

DIFF.

LL

LOW
LIMIT

DSBL

B

ZC

LINE VOLTAGE OIL
BURNER RELAY

B2

1

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

2

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

C1

C2

ZR

LEGEND: = LED

B1

M17776

Fig. 3. L7124U single zone connections.

3 69-1232—2