Installation, Operation and Maintenance Manual
VariCool EZ-Fit
26
Subject to change without notice.
Belt Tensioning
Excessive belt tension is the number one cause for blower
bearing failure Proper belt tension and pulley alignment are
essential for trouble free operation
Deflection is the amount the belt gives when force is applied,
usually by finger, to the belt at the approximate center point
to the belt span
Insufficient deflection indicates that the belt tension is
entirely too tight, and if not loosened somewhat, noise due
to excessive vibration, premature bearing failure, shortened
belt life, and a reduction in supply air blower performance
may result Tight belts may also overload the motor and
cause the efficiency to drop considerably or even premature
motor failure as well
Excessive deflection is an indication that the belt is not tight
enough If not corrected, slippage may occur causing loss of
blower speed and belt failure The belts will glaze then crack
or even break due to increased temperatures caused by
slippage Belts may slip during start-up, but slipping should
stop as soon as the fan reaches full speed
If the midpoint (midway between the blower and motor shaft)
of the belt is pressed inward, there should be about 1/2” to a
1” of deflection when the belt is properly tensioned
Refer to Figure 8 – Belt Tensioning below
Figure 8 – Belt Tensioning
For proper tensioning, use the following equation:
Deflection =
Belt Span
64
Belt span is in inches from center pulley to center pulley
(see Figure 8)
Belt tension is adjusted by using the adjusting bolt on the
end of the motor mounting frame
Check the alignment of the sheaves to make sure that the
sheave faces are in the same plane Check this by placing
a straight edge across the face of the sheaves Any gap
between the edge and sheave faces indicates misalignment
NOTE: This alignment method is only valid when the width of
the surfaces between the belt edges is the same for
both sheaves� When they are not equal or when using
adjustable pitch pulleys, adjust so that the belts have
approximately equal tension� Both shafts should be
at right angles to the belt. Check the setscrew and/or
bushing bolt tightness�
Belts tend to stretch somewhat after installation Recheck
belt tension after several hours of operation
Direct Drive Blowers
Verify the spring isolators have the shipping locks removed
and the leveling bolts are adjusted to the proper height
for suspension If the shipping locks are not removed and
adjusted, the fans will be very noisy and cause damage to
them
Deflection Point
Belt Span
INFORMATION
Some models of IDDP fans will have
a max impeller RPM that is less than
the motor built with it UCA factory will
program the VFD to maintain the de-rated
RPM required by the fan Reference the
table below for de-rated RPM values All
motors supplied operate at 3450 RPM at
60hz
Summary of Contents for VariCool EZ-Fit Series
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