Troubleshooting
Blower Does Not Operate
Proper supply power at | No |
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main disconnect |
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| Yes |
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24 VAC between | No |
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terminals R and X? |
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| Yes |
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24 VAC between | No |
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terminals G and X? |
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| Yes |
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24 VAC across | No |
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terminals 3 and X? |
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| Yes |
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24 VAC across | No |
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terminals 4 and X? |
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| Yes |
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24 VAC across A2 and A1 on | No |
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supply contactor (ST1) |
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| Yes |
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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)
Supply Fan Overload (ST1 OL) tripped
(Reset and check motor amps. Reference Blower
Optional Exhaust Fan Interlocks
(Correct/Replace)
(Optional) Freeze Protection (RT4) Tripped
(Reset)
(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)
Broken fan Bbelt
(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)
At this time the supply contactor (ST1) should pull in,
passing power to the supply motor and the blower should start.
26 | Model MSX | ® |
