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© FANTECH
2016
INSTALLATION, WIRING DIAGRAMS & FAN TROUBLE SHOOTING
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FAN TROUBLE SHOOTING
7.0 PERFORMANCE (Cont.)
Problem
Possible Cause
Recommended Action
7.1 Low air flow (Cont.)
The ductwork is undersized.
Check the ductwork and grilles are the
correct size. If smaller than design this
will increase the system resistance.
Fan speed is too low.
Check the motor speed and, if belt-
driven, the pulley ratios. If wrong change
to suit.
7.2 High 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.
If an axial fan check the pitch angle and,
if wrong, adjust.
The ductwork is oversized.
Check the ductwork and grilles are the
correct size. If larger than design this will
decrease the system resistance.
Fan speed is too high.
Check the motor speed and, if belt-
driven, the pulley ratios. If wrong change
to suit.
7.3 System resistance is greater
than estimated.
The ducting and/or the grilles, coils etc.
may be smaller than design, which will
increase the system resistance.
Check that the ductwork and system
components are the correct size. Check
that all dampers are open. Check that all
registers and grilles are open.
Check the ducting is clear of rubbish.
Check flexible connectors are installed
correctly.
Check if filters are dirty, clean or replace
as necessary. Check if coils are dirty and
clean them if necessary.
Check duct take-offs and general duct
fittings are correctly installed and of good
design.
7.4 System resistance is lower than
estimated.
If the duct system and associated
components are larger than design this
will reduce the system resistance.
Check the ductwork and associated
components are the correct size. Check
for leaks around flexible connections.
There may be leakage from the
ductwork.
Check the ductwork for leakage and
rectify as necessary.
Leakage around the base of Roof
Ventilators.
Ensure there is a proper seal between
the unit base and the up-stand. If there is
no seal then install one.