Instructions / Assembly
Table Of Contents
AT20, AT40, AT72D, AT87, AT88 AT TRANSFORMERS
69-1641EF—02 2
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 severe injury, death or property 
damage.
Disconnect power supply before beginning 
installation to prevent electrical shock or 
equipment damage.
Mounting the AT20A and AT40A 
Transformer
1. Mount the transformer to best suit the replacement 
application. The transformer may be mounted in 
one of three ways:
a. Use bolts in slots for direct mounting (Fig. 1).
Fig. 1. Use bolts in slots for panel mounting.
b. Horizontal channel frame. Place frame over 
laminations as shown in Fig. 3 and bend tabs 
over to hold transformer securely in place. 
Mount transformer over 3/16 in. (5 mm) holes 
in mounting feet. 
Fig. 2. Foot mounting (AT20C shown).
c. Vertical channel mounting. Place frame over 
laminations as shown in Fig. 3 and bend tabs 
over to hold transformer securely in place. 
Mount transformer through 3/16 in. (5 mm) 
holes in mounting feet.
Fig. 3. Use horizontal channel frame for horizontal foot 
mounting; vertical channel frame for vertical foot 
mounting.
ABC D E
in. mm in. mm in. mm in. mm in. mm
AT40C 2-13/32 61 7/8 22 1-3/4 44 2-3/16 56 2-7/8 73
AT87A 2-13/32 61 1 25 1-3/4 44 2-1/16 52 3 76
USE WASHERS
IF NECESSARY
PANEL
MOUNTING
M20654
M20655
USE SCREWS OR BOLTS
THROUGH SLOTS (4) IN
MOUNTING FEET
MOUNTING FOOT (2)
VERTICAL FOOT MOUNTING
M20657
BEND OVER TABS (4) TO 
SECURE TRANSFORMER
USE WASHERS
IF NECESSARY
M20665
HORIZONTAL FOOT MOUNTING
BEND OVER TABS (4) TO 
SECURE TRANSFORMER
USE WASHERS IF NECESSARY










