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Symptom Possible Cause Solution
Blower fails Blown fuse or open circuit breaker Replace fuse or reset circuit breaker and
to operate check amps
Broken fan belt Replace
Defective motor or capacitor Replace
Motor starter overloaded Reset starter and check amps
Motor overamps cfm too high Check cfm and adjust drives if needed
Static pressures are higher or lower If higher, ductwork should be improved
than design If lower, fan rpm 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 Unit 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 rpm
with catalog data
Dampers or registers closed. Open and adjust
Dirty or clogged filters Clean or replace
Leaks in ductwork. Repair
Elbows, or other obstructions
Correct or improve ductwork
may restrict fan outlet.
Belt slippage Adjust belt tension
Too much airflow Blower fan speed too high Check for correct fan rpm
Filter(s) not in place. Install filters
Insufficient static pressure (Ps) Induce Ps into system ductwork.
(airflow resistance)
Excessive noise Wheel rubbing on housing Center wheel
or vibration
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 in. 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
Wheel out of balance Replace or rebalance
Sheaves eccentric or out of balance Replace or rebalance
Accumulation of material on wheel Clean wheel and housing
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Trouble Shooting Instructions:
Blower System
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