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© FANTECH
2016
INSTALLATION, WIRING DIAGRAMS & FAN TROUBLE SHOOTING
FAN TROUBLE SHOOTING
N
5.0 ELECTRICAL (Cont.)
Problem
Possible Cause
Recommended Action
5.5 Motor overheating or high
current draw. (Cont.)
If the fan is a forward-curved centrifugal
there may be insufficient system
resistance.
Ensure the duct system is installed
correctly and, if necessary, lower the fan
speed.
Alternatively, increase the system
resistance by fitting perforated metal on
the fan inlet but note that this is
inefficient.
Axial fan impeller overpitched.
Re-pitch to the correct angle.
Error in the motor selection for the
required duty.
Check the motor nameplate and change
as necessary.
With belt-drive units incorrect pulley
selection or pulleys on the wrong shafts
Check the pulley ratio and that the
pulleys are on the correct shafts.
Gas density greater than design.
Increase the motor size to suit.
6.0 DUAL & TAP WOUND MOTORS
Problem
Possible Cause
Recommended Action
6.1 High current draw and/or
‘growling’ bearings
Tap-wound motors can create problems
if the 'star point' contactor is not
connected. The motor will be fine in low
speed but in high speed will have a high
current draw and a severe electrical
noise that sounds like noisy bearings.
The motor will not last long when run in
this condition.
Dual-wound motors are rarely a problem.
Faulty wiring in the switchboard, check
the correct contactor is connected.
7.0 PERFORMANCE
NOTE: Refer to Do’s and Don’ts section of this catalogue for design advice.
Problem
Possible Cause
Recommended Action
7.1 Low air flow
Faulty instruments
Ensure instruments are accurate and
calibrated where necessary.
The wrong size fan has been installed.
Check the fan specifications are correct
for the particular system.
The fan is running backwards.
Check rotation of the impeller. If the
rotation is wrong refer to the 'Electrical'
section above.
Pitch-angle of an axial fan may be wrong.
Check the pitch-angle against the
schedule, if wrong contact the supplier.
Site adjustment may be practical.
Fan speed is too slow.
Check the motor speed and, if belt-
driven, the pulley ratios. If wrong change
to suit.
The ductwork is undersized.
Check the ductwork and grilles are the
correct size. If smaller than design this
will increase the system resistance.
If a centrifugal fan check the cut-off
position.
Contact the supplier.
Bad installation.
Check the entry and discharge
conditions to the fan are of a good
design.
If the fan is mounted close to bends on
the intake or discharge this will impact on
the fans' performance.
Check there are no duct obstructions on
the intake or discharge of the fan.
Internal duct lining may have come
loose, check and repair.