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Symptom
Possible Cause
Blown fuse or open circuit
breaker.
Defective motor or capacitor.
Blower Fails to
Motor starter overloaded.
Operate
Electrical.
Drive.
Control power (24 Vac) wiring
run is too long (resistance
should not exceed 0.75 ohms).
Motor Starters
Incoming supply power is
"Chatter" or Do
less than anticipated. Voltage
Not Pull In
supplied to starter coil must
be within +10% / -15% of
nominal voltage stated on
the coil.
Cfm too high.
Static pressures are higher or
lower than design.
Blower rotation is incorrect.
Motor Over Amps
Motor voltage incorrect.
Motor horsepower too low.
Shorted windings in motor.
Unit damper not fully open.
System static pressure too high
Blower speed too low.
Fan wheels are operating
backwards.
Low Airflow (cfm)
Dirty filter or energy wheel.
Leaks in ductwork.
Elbows or other obstructions
may be obstructing fan outlet.
Belt slippage.
Blower fan speed too high.
Filter(s) not in place.
High Airflow (cfm)
Insufficient static pressure (Ps)
(airflow resistance).
* Always provide the unit model and serial number when requesting parts or service information. * Always check motor amps and compare to nameplate rating.
Trouble Shooting
Corrective Action
Replace fuse or reset circuit breaker and check amps.
Replace
Reset starter and check amps.
Check for On/Off switches. Check for correct supply voltage.
Check for broken or loose belts. Tighten loose pulleys.
Shorten wiring run to mechanical room or install a relay
which will turn unit on/off (C/F for relay information).
Need to increase supply power or use a special control
transformer which is sized for the actual supply power.
Check cfm and adjust drives if needed.
If higher, ductwork should be improved.
If lower, fan rpm should be lower.
Check rotation and reverse if necessary.
Check motor nameplate versus supplied voltage.
See specifications and catalog for fan curves to determine if
horsepower is sufficient.
Replace motor.
Adjust damper linkage or replace damper motor.
Improve ductwork to eliminate losses using good duct
practices.
Check for correct drives and rpm with catalog data.
For 3-phase see Fan Wheel Rotation on page 15.
Follow cleaning procedures on pages 18 and 21.
Repair.
Correct or improve ductwork.
Adjust belt tension.
Check for correct fan rpm. Decrease fan speed if necessary.
Install filters.
Induce Ps into system ductwork. Make sure grilles and
access doors are installed. Decrease fan speed if necessary.
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