* Always provide the unit model and serial number when requesting parts or service information. * Always check motor amps and compare to nameplate rating.
23
Control power (24 Vac) wiring
run is too long (resistance
should not exceed 0.75 ohms).
Shorten wiring run to mechanical room or install a relay
which will turn unit on/off (C/F for relay information).
Incoming supply power is
less than anticipated. Voltage
supplied to starter coil must
be within +10% / -15% of
nominal voltage stated on
the coil.
Need to increase supply power or use a special control
transformer which is sized for the actual supply power.
Motor Starters
“Chatter” or Do
Not Pull In
Blown fuse or open circuit
breaker.
Replace fuse or reset circuit breaker and check amps.
Possible CauseSymptom Corrective Action
Defective motor or capacitor. Replace
Motor starter overloaded. Reset starter and check amps.
Electrical. Check for On/Off switches. Check for correct supply voltage.
Drive. Check for broken or loose belts. Tighten loose pulleys.
Blower Fails to
Operate
Cfm too high. Check cfm and adjust drives if needed.
Static pressures are higher or
lower than design.
If higher, ductwork should be improved.
If lower, fan rpm should be lower.
Blower rotation is incorrect. Check rotation and reverse if necessary.
Motor voltage incorrect. Check motor nameplate versus supplied voltage.
Motor horsepower too low. See specifications and catalog for fan curves to determine if
horsepower is sufficient.
Motor Over Amps
Shorted windings in motor. Replace motor.
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.
Fan wheels are operating
backwards.
For 3-phase see Fan Wheel Rotation on page 15.
Dirty filter or energy wheel. Follow cleaning procedures on pages 18 and 21.
Leaks in ductwork. Repair.
Elbows or other obstructions
may be obstructing fan outlet.
Correct or improve ductwork.
Belt slippage. Adjust belt tension.
Blower fan speed too high. Check for correct fan rpm. Decrease fan speed if necessary.
Filter(s) not in place. Install filters.
Insufficient static pressure (Ps)
(airflow resistance).
Induce Ps into system ductwork. Make sure grilles and
access doors are installed. Decrease fan speed if necessary.
Low Airflow (cfm)
High Airflow (cfm)
Trouble Shooting