Cooling; Evaporator Coil - Carrier WeatherExpert 48LC 14 Series Service And Maintenance Instructions

FAN PULLEY
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
MOTOR PULLEY
Fig. 6 — Supply-Fan Pulley Adjustment
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 or use
the Packaged Rooftop Builder software program. Confirm that the
motor in this unit is capable of operating at the new operating con-
dition. Fan shaft loading increases 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 adjust-
MOVABLE
FLANGE
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
FIXED FLANGE
SINGLE - GROOVE
LOCKING COLLAR
T--- 25 TORX SOCKET
HEAD CAP SCREW
ment). This will reduce the amount of vibration generated by the
motor/belt-drive system.
To determine variable pitch pulley diameter, perform the follow-
ing calculation:
1. Determine full open and full closed pulley diameter.
2. Subtract the full open diameter from the full closed diameter.
3. Divide that number by the number of pulley turns open from
full closed.
This number is the change in pitch datum per turn open.
EXAMPLE
• Pulley dimensions 2.9 to 3.9 in.(full close to full open)
• 3.9 - 2.9 = 1
• 1 divided by 5 (turns from full close to full open)
• 0.2 change in pulley diameter per turn open
• 2.9 + 0.2 = 3.1-in. pulley diameter when pulley closed one
turn from full open
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this warning could cause personal injury,
death and/or equipment damage.
This system uses R-410A refrigerant, which has higher pres-
sures than R-22 and other refrigerants. No other refrigerant
may be used in this system. Gage set, hoses, and recovery sys-
tem must be designed to handle R-410A refrigerant. If unsure
about equipment, consult the equipment manufacturer.

Evaporator Coil

The evaporator coil is traditional round-tube, plate-fin technology.
Tube and fin construction is of various optional materials and
coatings (see Appendix A). Coils are multiple-row. On two com-
pressor units, the evaporator coil is a face split design, meaning the
two refrigerant circuits are independent in the coil. The bottom
portion of the coil will always be circuit A, with the top of the coil
being circuit B.
COIL MAINTENANCE
RECOMMENDATION
Routine cleaning of coil surfaces is essential to maintain proper
operation of the unit. Elimination of contamination and removal of
harmful residues will greatly increase the life of the coil and ex-
tend the life of the unit. The following maintenance and cleaning
procedures are recommended as part of the routine maintenance
activities to extend the life of the coil.
Remove Surface Loaded Fibers
Surface loaded fibers or dirt should be removed with a vacuum
cleaner. If a vacuum cleaner is not available, a soft non-metallic
bristle brush may be used. In either case, the tool should be ap-
plied in the direction of the fins. Coil surfaces can be easily dam-
aged (fin edges can be easily bent over and damage to the coating
of a protected coil) if the tool is applied across the fins.
NOTE: Use of a water stream, such as a garden hose, against a
surface loaded coil will drive the fibers and dirt into the coil. This
will make cleaning efforts more difficult. Surface loaded fibers
must be completely removed prior to using low velocity clean wa-
ter rinse.
Periodic Clean Water Rinse
A periodic clean water rinse is very beneficial for coils that are
applied in coastal or industrial environments. However, it is very
important that the water rinse is made with very low velocity
5

COOLING

WARNING
AND CLEANING