11
Model MSCF Modular Small Cabinet Fan
®
Symptom
Possible Cause
Corrective Action
Blower fails to
operate
Blown fuse or open circuit breaker
Replace fuse or reset circuit breaker and check amps
Broken fan belt
Replace
Defective motor or capacitor
Replace
Motor starter overloaded
Reset starter and check amps
Motor overamps
Airflow too high
Check airflow and adjust drives if needed
Static pressures are higher or lower
than design
If higher, ductwork should be improved
If lower, fan RPMs should be lower
Blower rotation is incorrect
Check rotation and correct
Motor voltage incorrect
Check motor nameplate and supplied voltage
Motor horsepower too low
See specifications and catalog for fan curves to determine
if horsepower is sufficient
Shorted windings in motor
Replace motor
Insufficient airflow
Mixing box damper not fully open
Adjust damper linkage or replace damper motor
System static pressure too high
Improve ductwork to eliminate losses using good duct
practices
Blower speed too low
Check for correct drives and RPMs with catalog data
Mixing box dampers closed
Open and adjust
Dirty or clogged filters
Clean or replace
Leaks in ductwork
Repair
Elbows, or other obstructions may
restrict fan outlet
Correct or improve ductwork
Belt slippage
Adjust belt tension
Unit running backwards
Correct as shown in System Start-Up section, Step #2,
page 10
Excessive dirt buildup on wheels
Clean wheel
Too much airflow
Blower fan speed too high
Check for correct fan RPM
Filter(s) not in place
Install filters
Insufficient static pressure
(airflow resistance)
Induce static pressure into system ductwork
Excessive noise or
vibration
Wheel improperly aligned and rubbing on
housing
Center wheel
Loose wheel on shaft
Tighten wheel setscrew
Loose motor or blower sheave
Tighten sheave setscrew
Belts too loose
Adjust belt tension after 24 hours of operation
Belts too tight
Loosen to maintain 3/8 inch deflection per ft. of span
between sheaves
Worn belt
Replace
Motor base or blower loose
Tighten mountings bolts
Worn bearings
Replace
Bearing and drive alignment
Realign
Motor out of balance
Replace
Unbalanced wheel caused by excessive
dirt and grease buildup
Replace or rebalance
Sheaves eccentric or out-of-balance
Replace or rebalance
Accumulation of material on wheel
Clean wheel and housing
Foreign objects in wheel or housing
Remove objects. Check for damage or unbalance.
Troubleshooting
NOTE
Before taking any corrective action, ensure unit is incapable of operation during repairs.