Variable Frequency Drive (Vfd); Belt; Adjustable-Pitch Pulley On Motor - Carrier WeatherMaster 50HCQ04-12 Service And Maintenance Instructions

MOUNTING
BOLTS (4)
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 sur-
faces. Check belt tension by using a spring-force tool, such as
Browning's "Belt Tension Checker" (P/N: 1302546) or equiva-
lent tool; tension should be 6 lbs at a
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
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 re-
duce 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 to 70 in.-lb (7.4 to 7.9 Nm).
BELT
DEFLECTION
Fig. 9 — Checking Blower Motor Belt Tension
REPLACING THE BELT
NOTE: Use a belt with same section type or similar size. Do not
substitute an 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.
BLOWER PULLEY
V--- BELT
MOTOR
PULLEY
MOTOR
MOTOR MOUNTING
PLATE
5 / -in. (1.6 cm) deflection
8
1 / -in. (1.3 cm) deflection is
2
STRAIGHTEDGE
BROWNING BELT
TENSION CHECKER
1/2"
(1.3 cm)
.
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.
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 to 70 in.-lb (7.4 to
7.9 Nm).
7. Check the tension after a few hours of runtime and read-
just as required.

Adjustable-Pitch Pulley on Motor

The motor pulley is an adjustable-pitch type that allows a ser-
vicer to implement changes in the fan wheel speed to match as-
installed ductwork systems. The pulley consists of a fixed
flange side that faces the motor (secured to the motor shaft)
and a movable flange side that can be rotated around the fixed
flange side that increases or reduces the pitch diameter of this
driver pulley. See Fig. 10.
FAN PULLEY
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
MOTOR PULLEY
Fig. 10 — Supply-Fan Pulley Adjustment
As the pitch diameter is changed by adjusting the position of
the movable flange, the centerline on this pulley shifts laterally
(along the motor shaft). This creates a requirement for a re-
alignment of the pulleys after any adjustment of the movable
flange. Reset the belt tension after each realignment.
Inspect the condition of the motor pulley for signs of wear.
Glazing of the belt contact surfaces and erosion on these sur-
faces are signs of improper belt tension and/or belt slippage.
Replace pulley if wear is excessive.
7
CAUTION
MOVABLE
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
FLANGE