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Troubleshooting
Blower Does Not Operate
Proper supply power at
main disconnect
Yes
24 VAC between
terminals R and C?
Yes
24 VAC between
terminals G and C?
Yes
24 VAC across
terminals 2 and C?
Yes
24 VAC across
terminals 4 and C?
Yes
24 VAC across A2 and A1 on
supply contactor (ST1)
Yes
®
No
No
Main Transformer (TR1) Defective
No
Fire system contact (FSC) tripped/not installed
No
Supply Fan Overload (ST1 OL) Tripped
(Reset and check motor amps, reference Blower Start-Up Step #4)
Optional Exhaust Fan Interlocks (ST2-ST5) Open
No
(Optional) Freeze Protection (RT4) Tripped
No
(Optional) Damper Limit Switch (DL1) Holding
(Wait for actuator to open fully or adjust limit switch)
(Optional) Damper Limit Switch Jumper Missing
(Install jumper, reference the unit ladder diagram for terminals)
(Check for loose connection) (Repair or replace relay)
(Replace - Reference V-Belt Drives in the Maintenance section)
One or more legs of 3 phase is out
At this time the supply contactor (ST1) should pull in,
passing power to the supply motor
Check Main Voltage
(See Blower Start-Up Step #1)
Main Disconnect (DS1) Off
(Turn Main Disconnect DS1 On)
Primary Fuses Blown
(Replace Fuses)
(Replace Transformer)
Supply Switch (S2) Off
(Turn Supply Switch (S2) On)
(Correct/Replace)
(Correct/Replace)
(Reset)
Fan Relay (RF) is not energized
Broken Fan Belt
Defective motor or capacitor
(Repair/Replace)
Blown Motor Fuse
(Replace)
(Restore missing legs)
and the blower should start.
Model IG / IGX Make-Up Air
21
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