MUA-SVX01A-EN • Direct-Fired Make-up Air
55
Maintenance
WARNING
Dangerous
Voltage!
Disconnect all electric power, including remote disconnects and discharge all
motor start/run capacitors before servicing. Follow proper lockout/tagout
procedures to ensure the power can not be inadvertently energized. Failure to
disconnect power before servicing could result in death or serious injury.
Belt Tensions and Adjustments
Belt tension is adjusted during the initial run-in and test periods at the factory.
However, belts are run as slack as possible to prevent excessive damage to the
bearings, yet tight enough to prevent slippage.
If necessary, tighten all belts during the first few months of operation, and verify
proper tension weekly during the first 60-days, after which, 30-day check intervals
are sufficient.
CAUTION
Equipment
Damage!
Tightening any belt or belts by changing the pitch of an adjustable pulley will
change the speed of a driven pulley. This could cause the unit to be rendered out
of air balance. Improper unit operation or motor failure could result.
Suggested Belt Tension Method
1.
Check tension frequently during the first 24 to 48-hours of run-in operation.
Ideal tension is the lowest tension at which the belt will not slip under peak
load conditions. Over tensioning shortens belt and bearing life.
2.
To properly tension a conventional V-belt drive, use the following method:
a. Measure the span length.
b. At the center of the span, apply a force perpendicular to the span to
deflect the belt 1/64-inch for every inch of span length. For example: for a
40-inch span, apply a force that will deflect the belt 40/64 or 5/8 of an inch.
c. Compare the force applied with the values given in Table 8. If the force is
between the values for normal tension and 1-1/2 times normal tension, the
belt tension should be satisfactory. If the belt tension is not within this
range, it can be adjusted by loosening the motor mounting bolts and
adjusting the position of the motor along its base.
Note: A new drive can be tightened to two times the minimum value shown to
allow for normal drop in tension during the run-in period.
Note 19.
For recommendations of other belt types, consult respective manufacturers.
Small Pulley Diameter Range in Inches
3.4-4.2
4.4-4.6
5.8-8.6
Belt Manufacturer & Belt Type
Gates Hi-Power
Pounds Force for Normal Tension
4.4
4.9
5.8
Pounds Force for 1 1/2 times Normal Tension
6.6
7.4
8.7
