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Model VSU Make-Up Air
®
Blower Does Not Operate
Troubleshooting
Proper supply power at
main disconnect
Check main voltage.
Reference: Start-Up - Blower, Check the Voltage, pg. 14
Main disconnect (DS1) off.
Turn main disconnect (DS1) on.
Primary fuses blown.
Replace fuses.
24 VAC between
terminals R and X?
Main transformer (TR1) defective.
Replace transformer.
24 VAC between
terminals G and X?
Supply switch (S2) off.
Turn supply switch (S2) on.
Fire system contact (FSC) tripped/not installed.
Correct, replace.
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Broken fan belt.
Replace.
Reference: Maintenance - Routine, V-Belt Drives, pg. 31
Defective motor or capacitor.
Repair, replace.
Blown motor fuse.
Replace.
One or more legs of three-phase is out.
Restore missing legs.
24 VAC across A2 and A1 on
supply contactor (ST1)
24 VAC across
terminals 4 and X?
24 VAC across
terminals 3 and X?
Supply fan overload (ST1 OL) tripped.
Reset and check motor amps.
Reference: Start-Up - Blower, Motor Check, pg. 14
Optional exhaust fan interlocks (ST2-ST5) open.
Correct, replace.
(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.
Fan relay (RF) is not energized.
Check for loose connection. Repair or replace relay.
(Optional) freeze protection (RT4) tripped.
Reset.
At this time the supply contactor (ST1) should
pull in, passing power to the supply motor
and the blower should start.