Troubleshooting; Blower Does Not Operate - Greenheck VSU Installation, Operation And Maintenance Manual

Vsu make-up air unit with direct-fired gas heater
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Troubleshooting

Blower Does Not Operate

Proper supply power at
main disconnect
Yes
24 VAC between
terminals R and X?
Yes
24 VAC between
terminals G and X?
Yes
24 VAC across
terminals 3 and X?
Yes
24 VAC across
terminals 4 and X?
Yes
24 VAC across A2 and A1 on
supply contactor (ST1)
Yes
22
Model VSU Make-Up Air
No
Reference: Start-Up - Blower, Check the Voltage, pg. 14
No
No
Fire system contact (FSC) tripped/not installed.
No
Supply fan overload (ST1 OL) tripped.
Reference: Start-Up - Blower, Motor Check, pg. 14
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 units ladder diagram for terminals.
Check for loose connection. Repair or replace relay.
Reference: Maintenance - Routine, V-Belt Drives, pg. 31
One or more legs of three-phase is out.
At this time the supply contactor (ST1) should
pull in, passing power to the supply motor
Check main voltage.
Main disconnect (DS1) off.
Turn main disconnect (DS1) on.
Primary fuses blown.
Replace fuses.
Main transformer (TR1) defective.
Replace transformer.
Supply switch (S2) off.
Turn supply switch (S2) on.
Correct, replace.
Reset and check motor amps.
Correct, replace.
Reset.
Fan relay (RF) is not energized.
Broken fan belt.
Replace.
Defective motor or capacitor.
Repair, replace.
Blown motor fuse.
Replace.
Restore missing legs.
and the blower should start.
®

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