9
Model G/GB Centrifugal Roof Exhaust Fans
®
Troubleshooting
WARNING: Before taking any corrective action, make certain unit is not capable of operation during repairs.
PROBLEM CAUSE CORRECTIVE ACTION
Excessive noise
or vibration
Wheel rubbing inlet
Adjust wheel and/or inlet cone. Tighten wheel hub or bearing collars
on shaft.
V-belt drive
Tighten pulleys on motor/fan shaft. Adjust belt tension. Align pulleys
properly, see page 6, Figure 9-10. Replace worn belts or pulleys.
Bearings
Replace defective bearing(s). Lubricate bearings. Tighten collars
and fasteners.
Wheel unbalance
Clean all dirt off wheel. Check wheel balance, rebalance in place if
necessary.
Belts too tight or too loose Adjust tension, see page 7, Figure 12a-b.
Wheel improperly aligned and
rubbing
Center wheel on inlet, see page 6, Figure 7.
Loose drive or motor pulleys Align and tighten. See “Pre-Starting Checks”, see page 6.
Foreign objects in wheel or housing Remove objects, check for damage or unbalance.
Fan base not securely anchored Secure properly.
Motor hood loose and rattling Tighten screws securing motor hood.
Defective or loose motor bearings Replace motor with same frame size, RPM-HP.
High horsepower
Fan
Check rotation of wheel, see page 6, Figure 8. Reduce fan speed.
Duct system
Resize ductwork. Check proper operation of face and bypass dampers.
Check filters and access doors.
Fan does
not operate
Electrical supply
Check fuses/circuit breakers. Check for switches off. Check for correct
supply voltage.
Drive Check for broken belts. Tighten loose pulleys.
Motor Assure motor is correct horsepower and not tripping overload protector.
Motor overloads
or overheats
Lubrication Check for excessive or insufficient grease in the bearing.
Mechanical
Replace damaged bearing. Relieve excessive
belt tension. Align bearings. Check for bent shaft.
Belt slippage
Adjust tension or replace bad belts, see page 6-7.
Over/Under line voltage Contact power company.
Incorrect wheel rotation Check motor wiring (page 4) verify motor is wired for correct rotation.
Wheel RPM too high
Check drives or slow down fan by opening variable pitch pulley on
motor shaft.
Undersized motor Check motor ratings with catalog speed and air capacity chart.
Motor wired incorrectly Check motor wiring to wiring diagram located on fan motor.
Reduced airflow
System resistance too high
Check system: Proper operation of backdraft or control dampers,
obstruction in ductwork, clean dirty filters.
Unit running backwards Correct as shown on page 6, Figure 8.
Excessive dirt buildup on wheels Clean wheel.
Improper wheel alignment Center wheel on inlets, see Pre-Starting checks on page 6, Figure 7.
Dampers closed Inspect and repair.
Blocked duct/clogged filter Clean or replace.
Belt slippage Replace and adjust tension.
Speed too slow Check for correct drives.
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