Carrier WeatherExpert 50LC 07 Series Service And Maintenance Instructions page 4

NOTE: Without the spring-tension tool, place a straight edge
across the belt surface at the pulleys, then deflect the belt at mid-
span using one finger to a /
1
2
Adjust belt tension by loosening the motor mounting plate front
bolts and rear bolt 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). Tighten all bolts when finished.
To replace the belt:
1. Use a belt with same section type or similar size. Do not sub-
stitute 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.
2. Loosen the motor mounting plate front bolts and rear bolts.
3. 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.
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 and then sliding the motor and plate away from the fan
housing until proper tension is achieved.
6. Check the alignment of the pulleys, adjust if necessary.
7. Tighten all bolts.
8. Check the tension after a few hours of runtime and re-adjust
as required.
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. 6.)
FAN PULLEY
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
MOTOR PULLEY
Fig. 6 — 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 realignment of
the pulleys after any adjustment of the movable flange. Also reset
the belt tension after each realignment.
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.
To change fan speed:
1. Shut off unit power supply.
-in. deflection.
MOVABLE
FLANGE
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
2. Loosen belt by loosening fan motor mounting nuts. (See
Fig. 5.)
3. Loosen movable pulley flange setscrew. (See Fig. 6.)
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 maximum
speed specified.
5. Set movable flange at nearest keyway of pulley hub and
tighten setscrew to torque specifications.
To align fan and motor pulleys:
1. Loosen fan pulley setscrews.
2. Slide fan pulley along fan shaft. Make angular alignment by
loosening motor from mounting.
3. Tighten fan pulley setscrews and motor mounting bolts to
torque specifications.
4. Recheck belt tension.
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. 7.)
Fig. 7 — 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 to 120 ± 12 in.-lb.
CHANGING FAN WHEEL SPEED BY CHANGING
PULLEYS
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 install a replacement motor
pulley with a smaller pitch diameter than provided on the original
factory pulley. Change fan wheel speed by changing the fan pulley
(larger pitch diameter to reduce wheel speed, smaller pitch diame-
ter to increase wheel speed) or select a new system (both pulleys
and matching belt(s)).
Before changing pulleys to increase fan wheel speed, check the
fan performance at the target speed and airflow rate to determine
new motor loading (bhp). Use the fan performance tables in
Appendix C or use the Packaged Rooftop Builder software pro-
gram. Confirm that the motor in this unit is capable of operating at
4
LOCKING COLLAR
T--- 25 TORX SOCKET
HEAD CAP SCREW