Evaporator Fan Service And Replacement; Belt Tension Adjustment; Evaporator-Fan Motor Replacement; Condenser-Fan Adjustment - Carrier 48AJ Operating And Service Manual

13. Reinstall drive belts. (Refer to Belt Tension Adjustment
section below.)
14. Visually inspect the assembly. If the shafts are overly mis-
aligned, the drive shaft flange will not be parallel with the
shaft flanges.
15. Recheck nut torque after 1 to 2 hours of operation. Bolts
tend to relax after being initially torqued.

Evaporator Fan Service and Replacement

1. Turn off unit power supply.
2. Remove supply-air section panels.
3. Remove belt and blower pulley.
4. Loosen setscrews in blower wheels.
5. Remove locking collars from bearings.
6. Remove shaft.
7. Remove venturi on opposite side of bearing.
8. Lift out wheel.
9. Reverse above procedure to reinstall fan.
10. Check and adjust belt tension as necessary.
11. Restore power to unit.
Belt Tension Adjustment —
1. Turn off unit power supply.
2. Loosen motor mounting nuts and bolts. See Fig. 38.
3. Loosen fan motor nuts.
4. Turn motor jacking bolts to move motor mounting plate
left or right for proper belt tension. A slight bow should
be present in the belt on the slack side of the drive while
running under full load.
5. Tighten nuts.
6. Adjust bolts and nut on mounting plate to secure motor in
fixed position. Recheck belt tension after 24 hours of
operation. Adjust as necessary. Refer to Installation In-
structions for proper tension values.
7. Restore power to unit.

Evaporator-Fan Motor Replacement

1. Turn off unit power supply.
2. Remove upper outside panel and open hinged door to
gain access to motor.
3. Fully retract motor plate adjusting bolts.
4. Loosen the 2 rear (nearest the evaporator coil) motor plate
nuts.
5. Remove the 2 front motor plate nuts and carriage bolts.
6. Slide motor plate to the rear (toward the coil) and remove
fan belt(s).
7. Slide motor plate to the front and hand tighten one of the
rear motor plate nuts (tight enough to prevent the motor
plate from sliding back but loose enough to allow the
plate to pivot upward).
To adjust belt tension:
CENTER DRIVE
SHAFT
Fig. 37 — Evaporator Fan Coupling
121
8. Pivot the front of the motor plate upward enough to allow
access to the motor mounting hex bolts and secure in
place by inserting a prop.
9. Remove the nuts from the motor mounting hex bolts and
remove motor.
10. Replace the locktooth washer under the motor base with a
new washer. Be sure that the washer contacts the motor
base surface.
11. Reverse above steps to install new motor.

Condenser-Fan Adjustment

1. Turn off unit power supply.
2. Remove fan guard.
3. Loosen fan hub setscrews.
4. Adjust fan height on shaft using a straightedge placed
across venturi and measure per Fig. 39.
5. Fill hub recess with permagum if rubber hubcap is missing.
6. Tighten setscrews and replace panel(s).
7. Turn on unit power.
Four-Inch Filter Replacement —
Change Mode variable is used to service the unit when 4-in.
filters are used. When the filters need to be changed, set
→
Service Test F.4.CH = YES. The unit will be placed in
Service Test mode and the economizer will move to the 40%
open position to facilitate removal of the 4-in. filters. After the
filters have been changed, set Service Test
return the unit to normal operation.
The economizer damper motor is a
Power Failure —
spring return design. In event of power failure, dampers will
return to fully closed position until power is restored.
Refrigerant Charge —
listed on unit nameplate. Refer to Carrier GTAC II; Module 5;
Charging, Recovery, Recycling, and Reclamation section for
charging methods and procedures.
Unit panels must be in place when unit is operating during
charging procedure.
NOTE: Do not use recycled refrigerant as it may contain
contaminants.
NO CHARGE — Use standard evacuating techniques. After
evacuating system, weigh in the specified amount of refriger-
ant from the unit nameplate.
LOW CHARGE COOLING — Connect the gage set and a
temperature measuring device to the liquid line. Ensure that all
condenser fans are operating. It may be necessary to block part
of the coil on cold days to ensure that condensing pressures are
high enough to turn on the fans. Adjust the refrigerant change
in each circuit to obtain 20 F ± 2° F of liquid subcooling with
the exceptions of 18 F ± 2° F for size 036 units and 15 F ± 2° F
for size 041 and 051 units.
NOTE: Indoor-air cfm must be within normal operating range
of unit.
FLEX SHAFT
MEMBER FLANGE
The 4-Inch Filter
→
F.4.CH = NO to
Amount of refrigerant charge is
SHAFT BEARINGS
A50-5146