Coils; Service; General; Fan Motor Replacement - Carrier 39LA-25 Installation, Start-Up And Service Instructions Manual

Then:
Motor Rpm x Motor Sheave
Fan Rpm =
Fan Sheave Pitch Diameter (in.)
Example:
Actual
Nameplate Motor
Rpm = 1760
Mtr Sheave Pitch
Diameter = 8.9 in.
Fan Sheave Pitch
Diameter = 12.4 in.
Fan Rpm = 1760 x 8.9 1760 x 9
= 12.4
= 1263 Rpm 1267 Rpm
Refer to Table 1, Physical Data for maximum allowable fan
speeds for standard wheels. Excessive fan speed may result in con-
densate carryover from cooling coil or fan motor overload and
wheel failure.
1. Check direction of rotation (see Fig. 52). Arrow on drive side
of fan housing indicates correct direction of rotation.
Fig. 52 — Fan Wheel Rotation
2. Check vibration. If excessive vibration occurs, check for the
following:
a. Variable sheave (if air balance of system has been
accomplished: replace sheave with fixed sheave for con-
tinuous application).
b. Drive misalignment.
c. Mismatched, worn or loose belts.
d. Wheel or sheaves loose on shaft.
e. Loose bearings.
f. Loose mounting bolts.
g. Motor out of balance.
h. Sheaves eccentric or out of balance.
i. Vibration isolators improperly adjusted.
j. Out-of-balance or corroded wheel (rebalance or replace
if necessary).
k. Accumulation of material on wheel (remove excess
material).

COILS

Chilled Water Coil
Typical coil vents, drains, and lifting points for the Chilled Water
Coil are shown in Fig. 32.
DX Coil
Charge refrigerant. Also refer to condensing unit service and in-
stallation instructions. Refrigerant operating charge for unit coil is
shown in Table 2.
Pitch Diameter (in.)
Approximate
1760
9.0 (OD)
12.5 (OD)
12.5

General

1. Place a suitable walkway to protect floor insulation whenever
entering the fan section.
2. Review Safety Considerations at beginning of these instruc-
tions. Good safety habits are important tools when perform-
ing service procedures.
3. To make speed measurements, use a strobe-style tachometer
or calculate per Step 6 of Start-Up, Check List on page 49.

Fan Motor Replacement

1. Shut off motor power.
2. Disconnect and tag power wires at motor terminals.
3. Loosen motor brace-to-mounting-rail attaching bolts. Loosen
belt tensioning bolts to adjust the motor position so V-belts
can be removed without stretching over grooves.
4. Mark belt as to position. Remove and set aside belts.
5. Remove motor to motor bracket holddown bolts.
6. Remove motor pulley and set aside.
7. Remove motor.
8. Install new motor. Reassemble by reversing Steps 1-6. Be
sure to reinstall multiple belts in their original position. Use a
complete new set if required. Do not stretch belts over
sheaves. Review the sections on motor and sheave installa-
tion, sheave alignment and belt tensioning discussed previ-
ously (Fig. 29 and 30).
9. Reconnect motor leads and restore power. Check fan for
proper rotation as described in Start-Up, Check List.

Coil Cleaning

DETERGENT

Spray mild detergent solution on coils with garden-type sprayer.
Rinse with fresh water. Check to ensure condensate line is free.
Excess water from cleaning may flood unit if condensate line is
plugged.
STEAM
Remove coil to facilitate cleaning and prevent damage to unit in-
sulation. See Coil Removal section on page 51.

Winter Shutdown (Chilled Water Coil Only)

It is recommended that auxiliary drain piping be added to coil pip-
ing if yearly winterizing of coils is anticipated. This auxiliary pip-
ing should be located at the highest and lowest point on the respec-
tive header connection for each coil.

ANTIFREEZE METHODS OF COIL PROTECTION

1. Close coil water supply and return valves.
2. Drain coil as follows:
3. Method I — 'Break' flange of coupling at each header loca-
tion. Separate flange or coupling connection to facilitate coil
draining.
4. Method II — Open both valves to auxiliary drain piping.
5. After coil is drained, Method I, connect line with a service
valve and union from upper nozzle to an antifreeze reservoir.
Connect a self-priming reversible pump between the low
header connection and the reservoir. Method II, make connec-
tion to auxiliary drain valves.
6. Fill reservoir with any inhibited antifreeze acceptable to code
and underwriter authority.
7. Open service valve and circulate solution for 15 minutes; then
check its strength.
50

SERVICE