Honeywell AT120A, AT140A, AT150A, AT175A User manual

1 69-0251—2
AT120A,AT140A,AT150A,AT175A
UniversalTransformers
These transformers are for use in 24 Vac nominal con-
trol 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” re-
quirements and are Underwriters Laboratories (UL) Inc.
listed under UL 1585. They can be mounted through a
7/8 in.knockoutontheaccessorymountingplate(included),
or with the integral mounting feet. See Table 1 for addi-
tional specifications.
TABLE 1—MODEL SPECIFICATIONS.
Application
Primary Secondary
Voltage
Model
Number
Input
Voltage
(60 Hz) Wiring Connections Open Circuit
At Rated
Power
Output Wiring Connections Output Rating at 100 Percent Power Factor
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
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
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. Installermustbeatrained,experiencedservicetechnician.
4. After installation is complete, check out product
operation as provided in these instructions.
CAUTION
Disconnect power supply before beginning installa-
tiontopreventelectricalshockorequipmentdamage.
The transformer may be mounted in one of three ways:
— foot mount,
— plate mount, or
— mount through outlet box knockout hole.
FOOT MOUNTING
Mount the transformer using screws (not supplied)
throughthefour3/16in. x3/8in.holesin themountingfeet.
Make line voltage primary connections within an approved
enclosure. See Fig. 1.
Discard the mounting plate.
C. H. • Rev. 2-94 • ©Honeywell Inc. 1994 • Form Number 69-0251—2
Fig. 1—Foot mounting.
USE SCREWS OR
BOLTS THROUGH
SLOTS (4) IN
MOUNTING FEET
SCREW TERMINALS
FOR SECONDARY
CONNECTIONS
MOUNTING
FOOT (2)
LEADWIRES
FOR PRIMARY
CONNECTIONS
M9161

69-0251—2 2
PLATE MOUNTING
Mounting Plate to Transformer
Mount the plate to the transformer in either of two
positions (see Fig. 2):
a. at the clamp on the primary end bell, or
b. at the laminations.
Fig. 2—Plate may be mounted to transformer
in either of two position.
To mount the plate at the 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 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 setscrew
securely against the rim of the hole. See Fig. 3. Avoid
damaging the leadwires with the screwdriver.
Fig. 3—When screw is tightened, clamp holds
plate on transformer.
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

3 69-0251—2
Fig. 4—Use screwdriver to pry out both
sections of knockout. Fig. 5—Mounting screw and tab hold plate on transformer.
IMPORTANT
MOUNT
TRANSFORMER
OTHER SIDE
M9163
TRANSFORMER
PLATE
1. Align the plate with the box to determine the proper
mounting holes. The mounting feet and secondary termi-
nals will be outside the box.
2. Remove the mounting hole knockouts if necessary.
3. Mount the plate on the outlet box using two screws
(obtained locally).
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
throughtheknockout.Donotmountthetransformerthrough
a plastic knockout.
2. 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 ordi-
nances. Disconnect power before making wiring connec-
tions 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 connec-
tor.3. Make secondary connections to 24 Vac control cir-
cuit.
To mount the plate at the laminations:
1. Removethelargerectangularknockoutin themount-
ing plate as shown in Fig. 4.
2. Hold the transformer so the clamp on the end bell
faces you.
3. Withthe keyhole slots up,fit the mountingplate over
the primary leadwires and end bell. Insert small tab at the
bottomofthe plateintothe slotinthetransformermounting
foot.
4. Insert the mounting screw (supplied) through the
holesasshowninFig. 5.Securetheplateto thetransformer,
but do not overtighten the screw.
Mounting Transformer and Plate on Outlet Box
The mounting plate may be mounted on 4 in. square
boxes, 2 x 4 in. rectangular boxes, and on 4 in. octagonal
boxes. See Fig. 4.
M9188
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.

69-0251—2 4
Home and Building Control Home and Building Control Helping You Control Your World
Honeywell Inc. Honeywell Limited—Honeywell Limitée
1985 Douglas Drive North 740 Ellesmere Road
Golden Valley, MN 55422 Scarborough, Ontario
M1P 2V9
Printed in China
Fig. 6—Schematics for single and multitap
transformers. Checkout
CAUTION
Do not short transformer secondary terminals.
Overloadcurrentprotectionisinherenton AT120,
AT140, and AT150. A fused 3.5 Amp secondary
is used on AT175.
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, assure proper primary and sec-
ondary voltages exist.
3. Ifvoltage readingsare incorrect,assure primaryvolt-
age connections are made properly.
4. Measure voltage again.
• If proper primary voltage is measured and sec-
ondary voltage is significantly less than the volt-
age shown on the regulation curves, transformer
winding is damaged. Replace transformer and
repeat checkout procedures.
• If primary voltage is 0V, assure power supply is
connected properly or repair if necessary. Repeat
checkout procedures.
5. Do not put system into operation unless correct pri-
mary and secondary voltages are measured.
VOLTAGE
VARIES
WITH MODEL
2
SECONDARY
M9182
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