Maintenance
28
SS-SVX004C-EN
Blower Belt Tensioning and Speed Adjustment
WARNING
Hazardous Voltage!
Disconnect all electric power, including remote
disconnects 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.
Figure 9.
Belt drive blower
Systems with belt drive blowers (refer to above figure) are
supplied with adjustable sheaves to change the blower
speed and adjustable motor bases for belt tensioning.
Perform the following procedure to change the blower
speed.
1. Turn the system off.
2. Turn off all power to the unit at the non-fused service
switch (RCU-O); use a lock-out/tag-out procedure. For
RCU-I, disconnect power to the unit at its main power
disconnect switch.
3. Remove the blower belt(s).
4. Loosen the set screw in the side of the sheave with an
Allen wrench.
5. Remove the sheave key.
6. Adjust the blower speed by closing the sheave one half
turn to increase speed or opening the sheave one half
turn to decrease speed.
7. Replace the sheave key and tighten set screw.
8. Proper belt tension is achieved when the belt has a
deflection of 1/2 inch per foot of span between the
blower and motor pulleys, with a firm pressure placed
on the side of the blower belt. Adjust the blower belt
tension by raising (to tighten) or lowering (to loosen)
the nuts on the adjustment rods of the motor base.
NOTICE
Belt Tension!
Do not over-tension belts as it could reduce fan and
motor bearing life, accelerate belt wear and possibly
cause shaft failure.
9. Restore power to the system.
10. Check the current draw on the blower motor to make
sure it does not exceed the nameplate rating of the
motor.
11. If current draw exceeds the nameplate rating of the
motor, repeat steps 1 through 10 to decrease blower
speed. If the motor pulls too much current, slow the
blower down by opening the adjustable sheave one
half turn at a time until the motor current is at or below
the nameplate FLA.
12. Check the motor overload on the blower starter to
confirm its setting is correct for the FLA of the motor.
Motor Base
Belt
Fixed Pulley
Blower
Tension Nut
Motor Base
Variable or
Addjustable
Pulley
Motor
Nameplate
Locknut
