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Honeywell AT150A User Manual

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INSTALLATION INSTRUCTIONS
69-0251-3
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. knock-
out 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 hazard-
ous 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.
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