Supply Fan (Blower) Section - Carrier 48TC 04 Series Service And Maintenance Instructions

SUPPLY FAN (BLOWER) SECTION

WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could cause personal
injury or death.
Before performing service or maintenance operations
on the fan system, shut off all unit power and
lock- - out the unit disconnect switch. Place tag on
switch to notify others maintenance is being done.
Do not reach into the fan section with power still
applied to unit.
Supply Fan (Belt- - Drive)
The supply fan system consists of a forward- - curved
centrifugal blower wheel on a solid shaft with two
concentric type bearings, one on each side of the blower
housing. A fixed- - pitch driven pulley is attached to the fan
shaft and an adjustable- - pitch driver pulley is on the
motor. The pulleys are connected using a "V" type belt.
See Fig. 5.
MOUNTING
BOLTS (4)
Fig. 5 - - Belt Drive Motor Mounting
Belt
Check the belt condition and tension quarterly.
(1.3 cm)
BELT
DEFLECTION
Fig. 6 - - Checking Blower Motor Belt Tension
BLOWER PULLEY
V-BELT
MOTOR
PULLEY
MOTOR
MOTOR MOUNTING
PLATE
C11504
STRAIGHTEDGE
BROWNING BELT
TENSION CHECKER
1/2"
C12093
Changing Fan Speed:
1. Shut off unit power supply.
2. Loosen belt by loosening fan motor mounting nuts.
See Fig. 5.
3. Loosen movable pulley flange setscrew. See Fig. 7.
4. Screw movable flange toward fixed flange to in-
crease 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.
Align fan and motor pulleys:
1. Loosen fan pulley setscrews.
2. Slide fan pulley along fan shaft. Make angular align-
ment by loosening motor from mounting.
3. Tighten fan pulley setscrews and motor mounting
bolts to torque specifications.
4. Recheck belt tension.
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 ⅝ - - in. (1.6cm) 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. See Fig. 6.
1. Place a straightedge along the belt between the two
pulleys.
2. Set the tension checker to the desired tension. Place
the large O- - ring at that point.
3. Press the tension checker downward on the belt until
the large O- - ring is at the bottom of the straightedge.
4. Adjust the belt tension as needed.
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 ½ - - in. deflection.
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
securely when finished.
Replacing the belt:
1. 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.
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.
6