Carrier 48TC series, Service And Maintenance Instructions, Page: 5 / 112

5
2. Loosen the two jack bolt locking nuts beneath the motor
mounting plate. Turn the jack bolt locking nut counterclock -
wise to loosen.
3. Turn the jack bolts counterclockwise to loosen and clockwise
to tighten.
4. Adjust the V-belt for proper tension.
5. Make sure the fan shaft and motor shaft are parallel before
tightening the motor mount nuts. See Fig. 7.
6. Make adjustments as necessary.
7. Tighten the four motor mounting nuts.
8. Check the V-belt tension. Make adjustments as necessary.
9. Re-tighten the four motor mounting nuts.
10. Tighten both jack bolt locking nuts securely.
Fig. 7 — Supply-Fan Pulley Adjustment
Replacing the V-belt:
1. Use a belt with same section type or similar size. Do not sub -
stitute a “FHP” or notched type V-belt.
2. Loosen (turn counterclockwise) the motor mounting plate
front bolts and rear bolts. See Fig. 5.
3. Loosen (turn counterclockwise) the jack bolt lock nuts.
Loosen (turn counterclockwise) the jack bolts, relieving the
belt tension and allowing easy removal of the belt by hand.
4. Remove the belt by gently lifting the old belt over one of the
pulleys.
5. Install the new belt by gently sliding the belt over both pul -
leys, then tighten (turn clockwise) the jack bolts, sliding the
motor plate away from the fan housing until proper belt ten -
sion is achieved.
6. Check the alignment of the pulleys, adjust if necessary. See
Fig. 7.
7. Tighten all bolts attaching the motor to the motor plate.
8. Tighten all jack bolt jam nuts by turning clockwise.
9. Check the tension after a few hours of runtime and re-adjust
as required. See Fig. 6.
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 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. 7.)
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 realignment of
the pulleys after any adjustment of the movable flange. Also reset
the belt tension after each realignment. The factory settings of the
adjustable pulley is five turns open from full closed.
Check the condition of the motor pulley for signs of wear. Glazing
of the belt contact surfaces and erosion on these surfaces are signs
of improper belt tension and/or belt slippage. Pulley replacement
may be necessary.
CHANGING FAN SPEED
1. Shut off the main unit power supply, and use the approved
lockout/tag-out procedures.
2. Loosen the belt by loosening the motor adjustment bolts as
described in the Belt Adjustment section. (See Fig. 6.)
3. Loosen the movable pulley flange setscrew. (See Fig. 7.)
4. Screw the movable flange toward fixed flange to increase
speed and away from fixed flange to decrease speed. Increas -
ing fan speed increases load on the motor. Do not exceed
maximum speed specified in the Product Data or motor
amperage listed on the unit rating plate.
5. Set the movable flange at the nearest keyway or flat of the
pulley hub and tighten the setscrew to torque of 72 ± 5 in.-lb
(8.14 ± 0.56 Nm).
ALIGNING THE FAN AND MOTOR PULLEYS
1. Loosen the fan pulley setscrews.
2. Slide the fan pulley along the fan shaft. Make angular align -
ment by loosening the motor from its mounting. See Fig. 6.
3. Tighten the fan pulley setscrews and motor mounting bolts to
torque specifications.
4. Recheck the belt tension. See Fig. 6.
Bearings
This fan system uses bearings featuring concentric split locking
collars. The collars are tightened through a cap screw bridging the
split portion of the collar. The cap screw has a Torx T25 socket
head. To tighten the locking collar: Hold the locking collar tightly
against the inner race of the bearing and torque the cap screw to
65 to 70 in.-lb (7.4 to 7.9 Nm). See Fig. 8.
Fig. 8 — Tightening Locking Collar
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.
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
FIXED FLANGE
MOVABLE
FLANGE
SINGLE - GROOVE
FAN PULLEY
MOTOR PULLEY
T --- 25 TORX SOCKET
HEAD CAP SCREW
LOCKING COLLAR