Carrier WeatherMaker 50KCQ A04 Series Service And Maintenance Instructions page 7

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 pulleys,
then sliding the motor and plate away from the fan hous-
ing until proper tension is achieved.
5. Check the alignment of the pulleys and 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 re-
adjust as required.
CAUTION
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.
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.
CHANGING THE FAN SPEED
1. Shut off unit power supply. Use proper lockout/tag-out
procedures.
2. Loosen belt by loosening fan motor mounting nuts. See
Fig. 8.
3. Loosen movable pulley flange setscrew. See Fig. 10.
MOVABLE
FLANGE
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
4. Screw movable flange toward fixed flange to increase
speed and away from fixed flange to decrease speed.
Increasing fan speed increases load on motor. Do not
exceed the maximum specified speed.
5. Set movable flange at nearest keyway of pulley hub.
Tighten setscrew and torque to 65 to 70 in. lb (7.4 to
7.9 Nm).
ALIGNING BLOWER AND MOTOR PULLEYS
1. Loosen blower pulley setscrews.
2. Slide blower pulley along blower shaft. Make angular
alignment by loosening motor mounting plate front and
rear bolts.
3. Tighten blower pulley setscrews and motor mounting
bolts. Torque bolts to 65 to 70 in. lb (7.4 to 7.9 Nm).
4. Recheck belt tension.
BEARINGS:
The fan system uses bearings featuring concentric split locking
collars. A Torx T-25 socket head cap screw is used to tighten
the locking collars. Tighten the locking collar by holding it
tightly against the inner race of the bearing. Tighten the socket
head cap screw. Torque cap screw to 55 to 60 in. lb (6.2 to
6.8 Nm). See Fig. 11. Check the condition of the motor pulley
for signs of wear. Glazing of the belt contact surfaces and ero-
sion on these surfaces are signs of improper belt tension and/or
belt slippage. Pulley replacement can be necessary.
Fig. 11 — Tightening Locking Collar
MOTOR
When replacing the motor, also replace the external-tooth lock
washer (star washer) under the motor mounting base; this is
part of the motor grounding system. Ensure the teeth on the
lock washer are in contact with the motor's painted base.
Tighten motor mounting bolts and torque to 120 ± 12 in. lb
(14 ± 1.4 Nm).
Change fan wheel speed by changing the fan pulley (larger
pitch diameter to reduce wheel speed, smaller pitch diameter to
increase wheel speed) or select a new system (both pulleys and
matching belt). The horsepower rating of the belt is primarily
dictated by the pitch diameter of the smaller pulley in the drive
system (typically the motor pulley in these units). Do not in-
stall a replacement motor pulley with a smaller pitch diameter
than was provided on the original factory pulley.
Before changing pulleys to increase fan wheel speed, check the
fan performance at the target speed and airflow rate to deter-
mine new motor loading (bhp). Use the fan performance tables
(pages 61 to 67) or use the Packaged Rooftop Builder software
program. Confirm that the motor in this unit is capable of oper-
ating at the new operating condition. Fan shaft loading increas-
es dramatically as wheel speed is increased.
To reduce vibration, replace the motor's adjustable pitch pulley
with a fixed pitch pulley (after the final airflow balance
adjustment). This will reduce the amount of vibration generat-
ed by the motor/belt-drive system.
7
LOCKING COLLAR
T--- 25 TORX SOCKET
HEAD CAP SCREW