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The percent of voltage imbalance is
then calculated:
100 x {[226-221] + [230-226] + [227-226]}
2 x 226
= 2.2% (Unacceptable)
In this example, 2.2 percent imbalance
is not acceptable and the power
company should be notified to correct
it.
7. Check unit vibration if the fan speed
is changed more than 5% from the
original designed rpm, or if parts
such as shafts, fan wheels, bear-
ings, or other drive components are
replaced. Do not exceed max. fan
rpm.
8. Pay particular attention to any
vibration, noise or overheating of the
motor and fan bearings.
(Bearings may run warm during
break in.)
Excessive Vibration
EXCESSIVE VIBRATION MUST BE
CORRECTED TO PREVENT BEAR-
ING AND SHAFT DAMAGE. SEE THE
SECTION
TITLED
"TROUBLE-
SHOOTING" FOR DETAILS ON THE
COMMON CAUSES FOR VIBRATION.
Determine Fan RPM
Fan rpm can be determined by using a
strobe-type tachometer, or revolution
counter.
Start - Up
Sheave Alignment
Align the fan and motor sheaves by
using a straightedge. The straightedge
must be long enough to span the
distance between the outside edges
of the sheaves. For more details refer
to maintenance section.
25
TRANE
R
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