1
69-0251—2
AT120A, AT140A, AT150A, AT175A
Universal Transformers
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. knockout on the accessory mounting plate (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. Installer must be a trained, experienced service technician.
4. After installation is complete, check out product
operation as provided in these instructions.
CAUTION
Disconnect power supply before beginning installa-
tion to prevent electrical shock or equipment damage.
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)
through the four 3/16 in. x 3/8 in. holes in the mounting feet.
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
