resideo AT120A User manual

INSTALLATION INSTRUCTIONS
69-0251-04
AT120A, AT140A, AT150A, AT175A
Universal Transformers
APPLICATION
These transformers are for use in 24 Vac nominal
control circuits. They are typically used in
heating/cooling control systems but can be used in any
application that does not exceed the load ratings. They
meet National Electrical Code Class 2 “not wet” and
Class 3 “wet” requirements and are Underwriters
Laboratories (UL) Inc. listed under UL 1585. They can be
mounted through a 7/8 in. knockout on the accessory
mounting plate (included), or with the integral mounting
feet. See Table 1 for additional specifications.
INSTALLATION
When Installing this Product...
1. Read these instructions carefully. Failure to follow
them could damage the product or cause a haz-
ardous 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.
CAUTION
Electrical Hazard.
Can cause electrical shock or equipment
damage.
Disconnect power supply before beginning
installation.
Mounting
The transformer can be mounted in one of three ways:
• foot mounting.
• plate mounting.
• mounting through outlet box knockout hole.
Foot Mounting
1. Mount the transformer using screws (not sup-
plied) through the four 3/16 in. x 3/8 in. holes in
the mounting feet.
2. Make line voltage primary connections within an
approved enclosure. See Fig. 1.
3. Discard the mounting plate.
Table 1. Model Specifications.
Model
Number
Primary Secondary
Output Rating at
100 Percent
Power Factor
Input
Voltage
(60 Hz)
Wiring
Connections
Voltage
Wiring
Connections
Open
Circuit
At Rated
Power
Output
AT120A 120/208/240 9 in. leads 27.0 24.0 Screw terminals 20 VA
AT140A 120 9 in. leads 27.0 24.0 Screw terminals 40 VA
120/208/240
120/240
208/240
AT150A 120/208/240 9 in. leads 27.5 24.0 Screw terminals 50 VA
AT175A 120/208/240 9 in. leads 27.5 24.0 Screw terminals 75 VA

AT120A, AT140A, AT150A, AT175A UNIVERSAL TRANSFORMERS
69-0251—04 2
Fig. 1. Foot mounting.
Plate Mounting
MOUNTING PLATE TO TRANSFORMER
Mount the plate to the transformer in either of two
positions (see Fig. 2):
• at clamp on primary end bell.
• at laminations.
Fig. 2. Mounting plate to transformer in either of two
positions.
MOUNTING PLATE AT CL AMP ON PRIMARY END BELL
1. Turn the screw on the clamp almost all the way
out.
2. Hold the mounting plate with the keyhole slots up
and the raised portion of the large center knockout
away from you.
3. From the back, thread the primary leadwires
through the round center hole in the plate.
4. Fit the clamp and screw through the round hole.
5. While holding the plate in place, tighten the set-
screw securely against the rim of the hole. See
Fig. 3. Avoid damaging the leadwires with the
screwdriver.
USE SCREWS OR
BOLTS THROUGH
SLOTS (4) IN
MOUNTING FEET
SCREW TERMINALS
FOR SECONDARY
CONNECTIONS
MOUNTING
FOOT (2)
LEADWIRES
FOR PRIMARY
CONNECTIONS
M9161
PLATE MOUNTED AT CLAMP ON PRIMARY END BELL
MOUNTING
PLATE
MOUNTING PLATE
PLATE MOUNTED AT THE LAMINATIONS
M9162
END
BELL
CLAMP SCREW
AND CLAMP
RAISED PORTION OF
LARGE CENTER KNOCKOUT
LEADWIRES
FOR PRIMARY
CONNECTIONS
LEADWIRES
FOR PRIMARY
CONNECTIONS
MOUNTING
SCREW SCREW
TERMINALS FOR
SECONDARY
CONNECTIONS
SCREW
TERMINALS FOR
SECONDARY
CONNECTIONS
MOUNTING FEET ON "A" MODELS ONLY.
1
1
1

AT120A, AT140A, AT150A, AT175A UNIVERSAL TRANSFORMERS
369-0251—04
Fig. 3. When screw is tightened, clamp holds plate on
transformer.
MOUNTING PL ATE AT L AMINATIONS
1. Remove the large rectangular knockout in the
mounting plate as shown in Fig. 4.
2. Hold the transformer so the clamp on the end bell
faces you.
3. With the keyhole slots up, fit the mounting plate
over the primary leadwires and end bell. Insert
small tab at the bottom of the plate into the slot in
the transformer mounting foot.
4. Insert the mounting screw (supplied) through the
holes as shown in Fig. 5. Secure the plate to the
transformer, but do not overtighten the screw.
MOUNTING TRANSFORMER AND PLATE ON OUTLET BOX
The mounting plate can be mounted on 4 in. square
boxes, 2 x 4 in. rectangular boxes, and on 4 in. octagonal
boxes. See Fig. 4.
1. Align the plate with the box to determine the cor-
rect mounting holes. The mounting feet and sec-
ondary terminals are outside the box.
2. Remove the mounting hole knockouts, if neces-
sary. Mount the plate on the outlet box using two
screws (obtained locally).
Mounting Through Outlet Box Knockout
Hole
The transformer can be mounted on an outlet box using
the clamp on the primary end bell. The mounting plate is
not used. To mount the transformer on an outlet box:
1. Turn the clamp screw almost all the way out.
2. From outside box, thread the primary leadwires
through suitable 7/8 in. knockout. Fit the clamp
and screw through the knockout. Do not mount the
transformer through a plastic knockout.
3. Tighten the clamp screw securely against the rim
of the knockout. Avoid damaging the leadwires
with the screwdriver.
Fig. 4. Use screwdriver to pry out both sections of
knockout.
Fig. 5. Mounting screw and tab hold plate on transformer.
M12126
M9188A
WITH RAISED PORTION OF KNOCKOUTS FACING YOU:
PRY UP TOP SECTION OF LARGE KNOCKOUT
BY INSERTING SCREWDRIVER FIRST AT ONE
SIDE OF SLOT AND THEN AT THE OTHER SIDE.
1.
THEN PRY UP BOTTOM SECTION OF KNOCKOUT.
2.
REMOVE BOTH SECTIONS OF KNOCKOUT WITH PLIERS.3.
SHADED AREAS REPRESENT KNOCKOUTS
AND SCREW SLOTS USED WITH 2 X 4 INCH
OR OCTAGONAL OUTLET BOXES.
IMPORTANT
MOUNT
TRANSFORMER
OTHER SIDE
M9163
TRANSFORMER
PLATE

AT120A, AT140A, AT150A, AT175A UNIVERSAL TRANSFORMERS
© 2020 Resideo Technologies, Inc. All rights reserved.
This product is manufactured by Resideo Technologies, Inc. and its affiliates.
www.resideo.com
Resideo Technologies, Inc.
1985 Douglas Drive North, Golden Valley, MN 55422
1-800-468-1502
69-0251—04 M.S. Rev. 08-20 | Printed in United States
Mounting Through Outlet Box Knockout
The transformer can be mounted on an outlet box using
the clamp on the primary end bell. The mounting plate is
not used. To mount the transformer on an outlet box:
1. Turn the clamp screw almost all the way out.
2. From outside box, thread the primary leadwires
through suitable 7/8 in. knockout. Fit the clamp
and screw through the knockout. Do not mount
the transformer through a plastic knockout.
3. Tighten the clamp screw securely against the rim
of the knockout. Avoid damaging the leadwires
with the screwdriver.
WIRING
All wiring must comply with local codes and ordinances.
Disconnect power before making wiring connections to
prevent electrical shock or equipment damage.
1. Make primary connections to the line voltage
power supply. On multitap models, be sure to use
correct leads for available power supply. See
Fig. 6.
2. On multitap models, insulate the ends of the
unused leads using wire nuts or capping with a
solderless connector.
3. Make secondary connections to 24 Vac control
circuit.
CHECKOUT
CAUTION
Voltage Check Hazard.
Overload current protection is inherent on
AT120, AT140, and AT150. A fused 3.5 Amp
secondary is used on AT175.
Do not short transformer secondary terminals.
Voltage Check
After installation is complete, turn on power supply and
perform a voltage check:
1. Place controlled equipment in operation and
observe through one complete cycle.
2. Using a voltmeter, check for proper primary and
secondary voltages.
3. If voltage readings are incorrect, be sure primary
voltage connections are made correctly.
4. Measure voltage again:
a. If correct primary voltage is measured and
secondary voltage is significantly less than
the voltage shown on the regulation curves,
transformer winding is damaged. Replace
transformer and repeat checkout procedures.
b. If primary voltage is 0V, be sure power supply
is connected correctly or repair, if necessary.
Repeat checkout procedures.
5. Do not put system into operation unless correct
primary and secondary voltages are measured.
Fig. 6. Schematics for single and multitap transformers.
VOLTAGE
VARIES
WITH MODEL
2
SECONDARY
M22974
COMMON
PRIMARY
BLACK
120 V - WHITE
208 V - RED
240 V - ORANGE
277 V - BROWN
480 V - BLACK/RED
1
3
SINGLE VOLTAGE MODELS
208 V
2
SECONDARY
COMMON
PRIMARY
BLACK
ORANGE
1
3
208/240 VAC MODELS
240 V RED
208 V
120 V
2
SECONDARY
COMMON
PRIMARY
BLACK
ORANGE
1
1 SECONDARY CONNECTIONS ARE SCREW TERMINALS, 1/4 INCH
QUICK-CONNECTS OR BLUE AND YELLOW LEADWIRES.
BLACK IS COMMON WITH RESPECT TO THE TRANSFORMER
WINDING ONLY AND NOT THE EXTERNAL CIRCUIT.
SOME MODELS AVAILABLE WITH 1/4 INCH QUICK CONNECTS.
2
3
3
120/208/240 VAC MODELS
240 V RED
WHITE
COMMON
BLACK
120 V
WHITE
240 V
ORANGE
PRIMARY SECONDARY
3
1
2
120/240 MODELS