TL;DR
An aeration fan that will not start is usually a tripped overload, a failed contactor, or a supply power issue. Check the overload relay, measure supply voltage, and inspect the contactor before replacing the motor.
What you might see
- fan control shows run command but fan does not start
- overload relay tripped indicator on the control panel
- no air movement from the aeration duct
- motor hum but no rotation on startup
Likely causes
Overload relay tripped from a locked rotor or high ambient temperature
Contactor coil failed or main contacts pitted from wear
Supply power phase lost from a blown fuse or open feeder
Motor winding fault from moisture ingress in an outdoor installation
Required tools
- Multimeter rated for supply voltage
- Megohmmeter (500V)
- LOTO kit
Safety first
- All energized electrical work requires category-rated PPE.
- Outdoor aeration fans in humid grain environments are at elevated risk of winding moisture faults. Never restart a motor that has been exposed to standing water without an insulation resistance check.
Procedure
- 1
Check the overload relay on the motor starter. If tripped, determine whether the bin is in a heat emergency requiring immediate fan operation. Press reset once after allowing 10 minutes for cooling.[1]
- 2
If the overload trips again on restart, do not keep resetting. Investigate the cause before any further reset attempt.
- 3
Measure supply voltage at the starter terminals L1, L2, L3 with a multimeter rated for the supply voltage.
Warning: Energized electrical measurement requires category-rated PPE and appropriate authorization. - 4
Compare each phase voltage to the nameplate. A phase loss or significant imbalance will cause the motor to stall or hum without starting.[1]
- 5
Check the contactor. Energize the coil manually and verify all three main contacts close simultaneously. Pitted or welded contacts require contactor replacement.
- 6
If supply and contactor are healthy, disconnect the motor leads and megger the windings to check for winding-to-ground fault. Outdoor motors are exposed to moisture.
- 7
Replace the motor if insulation resistance is below 1 MΩ. Replace the contactor or overload relay if faults are found in those components.
Sources
Brock Grain Systems Brock M-Series Grain Silo / Storage Bin general technical documentation, Brock Grain Systems
Grain bin aeration fan motor diagnostics and starter maintenance, general grain storage practice (general)
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