Installation, Operation and Maintenance Manual
VariCool
®
VAV
18
Subject to change without notice.
10.20-IM (0818)
Blower Speed Adjustment
Blower speed may be changed by adjusting the variable
diameter sheave provided on the blower drive motor
Sheave may be adjusted by removing the belt and loosening
the setscrew located in the hub of the outer flange. With the
setscrew loosened, the flange may be turned clockwise
to increase blower speed or counter-clockwise to reduce
blower speed
Typically the motor and drive packages have been sized and
designed for the specific CFM and external static pressure
(ESP) of the application. Before making any changes confirm
what the performance was designed for and what the actual
performance is
INFORMATION
Setscrew must be positioned directly
above the flat section of the threaded
sheave shaft before tightening to hold
adjustment
INFORMATION
Reduction of airflow through excessive
external air friction losses, lowered blower
speed operation with dirty filters, or
obstructed air flow may result in excessive
condensation at air outlets, short cycling,
or total unit shut- down due to evaporator
coil icing
INFORMATION
Verify that the motor current draw does
not exceed the motor nameplate current
by more than 10%
Blower Bearing Lubrication
INFORMATION
Unit must be shut off at the disconnect
switch before the blowers are serviced
Bearings on the smaller units are permanently sealed, but
should be checked periodically for signs of wear
Larger units have pillow block bearings Bearings will need
to be lubricated based on the use of the equipment
Duty
Grease Interval
Low Usage
12 Months
Periodic
6 Months
Continuous
1 – 2 Months
Use a high quality lithium grease for blower pillow block
bearings. Wipe off the “Zerk” fitting with a rag before adding
grease so as not to introduce dirt into the bearing
Slowly rotate the shaft while pumping it in Pump the grease
in slowly so as not to blow out the bearing seal When the
grease starts to “seep” out of the bearing you have put in
enough new lubricant
Over lubricating can cause a bearing to fail from overheating
or it can blow out the seal
Both excessive or inadequate grease may cause premature
failure Provided there is some grease in the bearings for
lubrication, under lubrication is better than over lubrication
as grease can easily be added but not removed Always
allow a slight bead around the circumference of the seals to
protect the bearing from foreign matter and helps flush out
the bearing as well
Wipe off the “Zerk” fitting with a rag after adding grease
Belts
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.
Содержание VariCool VAV
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