Greenheck MSX (470658) - Manual (Page 27)

27 Modular Supply Make-Up Air Unit
®
Proper supply power at
main disconnect
24 VAC between
terminals R and X?
24 VAC between
terminals G and X?
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Blower Does Not Operate
24 VAC across A2 and A1 on
supply contactor (ST1)
24 VAC across
terminals 4 and X?
24 VAC across
terminals 3 and X?
Troubleshooting
Check main voltage
(See Blower Start-Up Step #1)
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)
Fire System Contact (FSC) tripped/not installed
(Correct/Replace)
Broken fan belt
(Replace. Reference Maintenance section)
Defective motor or capacitor
(Repair/Replace)
Blown motor fuse
(Replace)
One or more legs of 3 phase is out
(Restore missing legs)
Supply Fan Overload (ST1 OL) tripped
(Reset and check motor amps. Reference Blower Start-Up #4)
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 unit’s 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.