SECTION 4
®SULLAIR®
28
3700 Operator’s Manual and Parts List
1. Check incoming voltage. Be sure that compressor is 
wired for the correct incoming voltage.
2. Check the motor starter for correct size, properly 
sized overload relay, and correct heaters for the 
load.
3. Check all electrical connections for tightness. Check 
all grounding connection for bond.
4. “DRY RUN” the electrical controls by disconnecting 
the three (3) motor leads from the starter. Energize 
the control circuits by pressing the “I” (START) pad, 
and check all protective devices to be sure that they 
will de-energize the starter coil when tripped.
5. Reconnect the motor leads and jog the motor for a 
direction of rotation check as explained in Section 
4.7.  Wiring diagram for standard compressors is 
supplied with the machine.
4.7 MOTOR ROTATION DIRECTION 
CHECK 
Motor rotation check must be made at compressor start-
up. The compressor will not operate correctly if it runs in 
the wrong direction. Open the compressor door to view 
the motor rotation. After the electrical wiring has been 
done, it is necessary to check the direction of the motor 
rotation.  Pull out the EMERGENCY STOP button and 
press once, quickly and in succession, the “I” (START) 
and “O” (STOP) pads. This action will bump start the 
motor for a very short time. When looking at the motor 
from the end opposite the compressor unit, the shaft 
should be turning clockwise. If the reversed rotation is 
noted, disconnect the power to the starter and exchange 
any two of the three power input leads, then re-check 
rotation. A “Direction of Rotation” decal is located on the 
motor to show proper motor/compressor rotation. An 
alternative to this procedure is to set the Microprocessor 
to display P1 sump pressure.  Pull out the EMERGENCY 
STOP button and press once, quickly and in succession, 
the “I” (START) and “O” (STOP) pads.  This action will 
bump start the motor for a very short time. If motor 
rotation is correct there will be immediate pressure 
shown. If no pressure is present, reverse rotation is 
occurring. Disconnect the power to the starter and 
exchange any two of the three power input leads.  
Recheck rotation as outlined above. 
4.8 FAN MOTOR ROTATION CHECK
On initial start-up check that the fan is rotating in the 
proper direction. The correct rotation is counterclockwise 
when viewing the fan motor from the driveshaft end.
A DANGER
Lethal shock hazards exist inside. 
Disconnect all power at source and lock 
out before opening or servicing.
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