Carrier 39LA25 Installation, Start-Up And Service Instructions Manual Download

Page: 50 / 60

Then:

Example:

Actual

Approximate

Nameplate Motor



Rpm =

1760

Mtr Sheave Pitch



Diameter

8.9 in.

9.0 (OD)

Fan Sheave Pitch



Diameter

12.4 in.

12.5 (OD)

Fan Rpm

1760 x 8.9 1760 x 9

12.4

12.5

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.

SERVICE

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.

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.