Instructions / Assembly

AT20, AT40, AT72D, AT87, AT88 AT TRANSFORMERS
5 69-1641EF—02
Fig. 9. Location of mounting holes.
Mounting the AT87 Transformer
Foot Mounting (Fig. 10)
Use screws or bolts through slots in the mounting feet to
fasten the transformer to the mounting surface.
Fig. 10. Foot mounting of AT87 Transformer.
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 mounting
plate (see Fig. 6).
2. Take transformer in one hand and mounting plate
in the other hand. Keyhole slots on mounting plate
should be up.
3. Place large knockout in mounting plate over
primary 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 (see Fig.
7).
4. Insert the mounting screw through the holes as
illustrated (Fig. 8).
5. Secure plate to transformer. Do not overtighten
screw.
Mounting Transformer and Plate to
Electrical Box.
The mounting plate can be mounted in 4 in. x 4 in. boxes
with regular and irregular spaced mounting holes, and on
4 in. octagonal boxes (Fig. 9).
1. Use the screws supplied with the junction box.
2. Place the screws through the appropriate mount-
ing holes in the plate and secure the transformer
and plate to the box.
3. Punch out appropriate knockouts for plate
mounting holes, as necessary.
NOTE: Transformer should always be outside of the
junction box.
Mounting the AT88 Transformer.
Use screws or bolts through slots in the mounting feet to
fasten the transformer to the mounting surface. See
Fig. 2.
WIRING
1. Disconnect power supply before installing
transformer. All wiring must comply with local
electrical codes and ordinances. Tape all unused
exposed leadwires separately.
2. Connect primary leadwires to line voltage power
supply. See Fig. 11 through Fig. 13.
3. Connect transformer secondary leadwires to 24
Vac control system.
Fig. 11. AT20/AT40 Transformer schematic.
Fig. 12. AT72D, AT87A Transformer schematic.
OCTAGON
BOX
M20658
IRREGULAR
4 X 4 INCH
BOX
(MOUNTING
HOLES IN
BOX ARE
SLIGHTLY
INDENTED)
REGULAR
4 X 4 INCH
BOX (2)
IRREGULAR
4 X 4 INCH
BOX
(MOUNTING
HOLES IN
BOX ARE
SLIGHTLY
INDENTED)
REGULAR
4 X 4 INCH
BOX (2)
OCTAGON
BOX
LOAD
N.E.C. CLASS 2
USE SCREWS OR
BOLTS THROUGH
SLOTS (4) IN
MOUNTING FEET
M20659
MOUNTING FOOT (2)
SCREW
TERMINALS
FOR
SECONDARY
CONNECTIONS
LEADWIRES
FOR PRIMARY
CONNECTIONS
SECONDARY CONNECTIONS ARE BLUE AND YELLOW
LEADWIRES.
BLACK IS COMMON WITH RESPECT TO THE TRANSFORMER
WINDING ONLY AND NOT THE EXTERNAL CIRCUIT.
WHITE (120V) OR ORANGE (240V)
COMMON
1 24 VAC
2
BLACK
1
2
M20660
1
1 SECONDARY CONNECTIONS ARE SCREW TERMINALS.
2 BLACK IS COMMON WITH RESPECT TO THE TRANSFORMER
WINDING AND NOT THE EXTERNAL CIRCUIT.
2
120 VAC
WHITE
208 VAC
240 VAC
BLACK
RED
ORANGE
24 VAC
M18321