7
the fan shaft and an adjustable−pitch driver pulley is on
the motor. The pulleys are connected using a V−belt. See
Fig. 8.
BLOWER PULLEY
V-BELT
MOTOR
PULLEY
MOTOR
MOTOR MOUNTING
PLATE
MOUNTING
BOLTS (4)
C11504
Fig. 8 − Typical Belt Drive Motor Mounting
Variable Frequency Drive (VFD)
For units equipped with a VFD factory installed option
(FIOP), refer to the following supplement: “Variable
Frequency Drive (VFD) Installation, Setup and
Troubleshooting.”
Belt
Check the belt condition and tension quarterly. Inspect the
belt for signs of cracking, fraying or glazing along the
inside surfaces. Check belt tension by using a spring−force
tool, such as Browning’s “Belt Tension Checker” (p/n:
1302546 or equivalent tool); tension should be 6−lbs at a
5
/
8
−in (1.6 cm). deflection when measured at the
centerline of the belt span. This point is at the center of
the belt when measuring the distance between the motor
shaft and the blower shaft.
NOTE: Without the spring−tension tool, place a straight
edge across the belt surface at the pulleys, then push down
on the belt at mid−span using one finger until a
1
/
2
−in.
(1.3 cm) deflection is reached. See Fig. 9.
Adjust belt tension by loosening the motor mounting plate
front and rear bolts and sliding the plate toward the fan (to
reduce tension) or away from fan (to increase tension).
Ensure the blower shaft and the motor shaft are parallel to
each other (pulleys aligned). When finished, tighten all
bolts and torque to 65−70 in−lb (7.4 to 7.9 Nm).
BROWNING BELT
TENSION CHECKER
STRAIGHTEDGE
1/2”
(1.3 cm)
BELT
DEFLECTION
C12093
Fig. 9 − Checking Blower Motor Belt Tension
Replacing the Belt:
NOTE: Use a belt with same section type or similar size.
Do not substitute a FHP−type belt. When installing the
new belt, do not use a tool (screwdriver or pry−bar) to
force the belt over the pulley flanges, this will stress the
belt and cause a reduction in belt life. Damage to the
pulley can also occur.
Use the following steps to replace the V−belt. See Fig. 8.
1. Loosen the front and rear motor mounting plate bolts.
2. Push the motor and its mounting plate towards the
blower housing as close as possible to reduce the
center distance between fan shaft and motor shaft.
3. Remove the belt by gently lifting the old belt over
one of the pulleys.
4. Install the new belt by gently sliding the belt over
both pulleys and then sliding the motor and plate
away from the fan housing until proper tension is
achieved.
5. Check the alignment of the pulleys, adjust if necessary.
6. Tighten all bolts and torque to 65−70 in−lb (7.4 to 7.9
Nm).
7. Check the tension after a few hours of runtime and
re−adjust as required.
EQUIPMENT DAMAGE HAZARD
Failure to follow this CAUTION can result in
premature wear and damage to equipment.
Do not use a screwdriver or a pry bar to place the new
V−belt in the pulley groove. This can cause stress on
the V−belt and the pulley resulting in premature wear
on the V−belt and damage to the pulley.
CAUTION
Adjustable−Pitch Pulley on Motor:
The motor pulley is an adjustable−pitch type that allows a
servicer to implement changes in the fan wheel speed to
match as−installed ductwork systems. The pulley consists
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