Instructions / Assembly

AT20, AT40, AT72D, AT87, AT88 AT TRANSFORMERS
3 69-1641EF—01
Mounting the AT72D
Transformer.
Mount the transformer to meet the application. Use
one of the methods illustrated. The transformer can be
mounted in any position.
Foot Mounting.
1. Discard mounting plate.
2. Use screws or bolts through slots in mounting
feet to fasten transformer to mounting surface
(see Fig. 2).
Plate Mounting.
The mounting plate allows the transformer to be
mounted on a 4 in. by 4 in. square or 4 in. octagonal
junction box.
1. Remove the large center knockout in the mount-
ing plate (Fig. 6).
2. Take transformer in one hand and mounting
plate in the other hand. Keyhole slots on mount-
ing plate should be up.
3. Place large knockout in mounting plate over pri-
mary leadwires and end bell of transformer. The
small tab on the bottom center of the plate fits
into the slot in the transformer mounting feet
(Fig. 7).
4. Insert the mounting screw through the holes as
illustrated.
5. Secure the plate to the transformer. Do not
overtighten.
Mounting plate to transformer (Fig. 4).
The plate can be mounted to the transformer in one of
two positions:
a. at the clamp on primary end bell (trans-
former all above plate);
b. at the laminations (transformer 3/4 above
plate. To mount the plate at clamp on pri-
mary end bell (transformer all above plate):
1. Take mounting plate in one hand. Keep the key-
hole slots up and the raised portion of the large
center knockout toward you.
2. Insert the primary leadwires through the center
hole in the plate.
3. Fit the hole in the plate over the clamp attached
to the end bell. Clamp screw must be turned
almost completely out.
4. With the plate in place over the clamp, tighten
the screw securely against the rim of the round
hold See Fig. 5. Avoid damaging the leadwires
with the screwdriver.
To mount the plate at the laminations (transformer
3/4 above the mounting plate:
1. Remove the large center knockout in the mount-
ing plate (see Fig. 6).
2. Take the transformer in one hand. Clamp on end
bell should face you.
3. Take the mounting plate in the other hand. Key-
hole slots should be up.
4. Place large knockout in mounting plate over
primary leadwires and end bell. Small tab at the
bottom of the center of the plate fits into the
transformer mounting foot (Fig. 7). Insert
mounting screw through holes as shown in Fig.
8.
5. Secure plate to transformer. Do not overtighten
screw.
Mounting Transformer and Plate to
Electrical Box
The mounting plate can be mounted to 4 in. x 4 in.
boxes with regular and irregular spaced mounting
holes, to 2 in by 4 in. boxes and to 4 in. octagonal
boxes. See Fig. 9.
1. Use the screws supplied with the electrical box.
2. Place them through the proper mounting holes
in the plate and secure the transformer and
plate to the box.
3. Punch out appropriate knockouts for plate
mounting holes, if necessary.
NOTE: Transformer feet should always be outside of
the junction box.
Clamp Mounting Using Junction Box
Knockout
The transformer can also be clamp mounted using a
junction box knockout, if desired. This mounting
option does not require the use of the mounting plate.
To mount the transformer within the knockout:
1. Insert the primary leadwires and clamp and
screw on transformer end bell through suitable
1/2 in. (13 mm) knockout in junction box. Clamp
screw must be turned almost completely out in
order to get clamp through knockout.
2. Tighten clamp screw securely against rim of
knockout. Avoid damaging the leadwires with the
screwdriver.