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Troubleshooting – Unit
Symptom
Possible Cause
Blown fuse or open circuit breaker.
Defective motor or capacitor.
Blower fails to
operate
Motor overloaded.
Electrical.
One or both
Blower fan motor overloads are tripping and auto-
blowers turn off
resetting.
intermittently and
back on after two
Exhaust only frost control sensors are tripping.
minutes
Control power (24 VAC) wiring run is too long.
(Resistance should not exceed 0.75 ohms).
Motor starters
"chatter" or do not
pull in
Incoming supply power is less than anticipated.
Voltage supplied to starter coil must be within
+10% / -15% of nominal voltage stated on the coil.
Static pressures are higher than design.
Motor voltage incorrect.
Motor over amps
Motor horsepower too low.
Shorted windings in motor.
Unit damper not fully open.
System static pressure too high.
Blower speed too low.
Low airflow (cfm)
Fan wheels are operating backwards.
Dirty filter.
Leaks in ductwork.
Elbows or other obstructions may be obstructing
fan outlet.
Blower fan speed too high.
High airflow (cfm)
Filter(s) not in place.
Insufficient static pressure (Ps).
(airflow resistance)
Fan wheel rubbing on inlet.
Bearings.
Excessive noise or
Loose wheel on shaft.
vibration
Motor base or blower loose.
Noise being transmitted by duct.
Corrective Action
Replace fuse or reset circuit breaker and check
amps.
Replace.
Reset VFD and check amps.
Check for On/Off switches. Check for correct
supply voltage. Check Control wiring.
Decrease fan speed.
Adjust frost temperature sensor set point as
needed.
Shorten wiring run to mechanical room or install a
relay to turn unit on/off. Consult factory for relay
information. Increase wire gauge size so that
resistance is 0.75 ohms or less.
Need to increase supply power or use a special
control transformer which is sized for the actual
supply power.
Check for dirty filters. Improve ductwork.
Check motor wiring. 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 maximum motor RPM and compare with
catalog data. Verify that external control wiring is in
place if required.
For 3-phase, see Direction of Fan Wheel Rotation in
Start-Up Components section.
Replace filters or follow cleaning procedures in
Routine Maintenance section of this manual.
Repair.
Correct or improve ductwork.
Check for correct maximum fan RPM. Decrease
maximum fan speed if necessary with the variable
frequency drive.
Install filters.
Induce Ps into system ductwork. Make sure grilles
and access doors are installed. Decrease fan speed
if necessary.
Adjust wheel and/or inlet cone. Tighten wheel hub
or bearing collars on shaft.
Replace defective bearing(s). Lubricate bearings.
Tighten collars and fasteners.
Tighten wheel hub.
Tighten mounting bolts.
Make sure ductwork is supported properly. Make
sure ductwork metal thickness is sized for proper
stiffness. Check duct size at discharge to ensure
that air velocities are not too high.
VersiVent Energy Recovery Ventilator
35
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