10
plate to the unit. Discard all lock washers.
9. Remove motor and motor mounting bracket from
unit.
10. Remove four bolts, flat washers, lock washers and
single external--t ooth lock washer attaching motor t o
the motor mounting plate. Discard all lock washers
and external--tooth lock washer.
11. Lift motor from motor mounting plate and set aside.
12. Slide motor mounting band from old motor.
13. Slide motor mounting band onto new motor and set
motor onto the motor mounting plate.
14. Remove variable pitch pulley from old motor and
attach it to the new motor.
15. Inspect variable pitch pulley for cracks and wear.
Replace the pulley if necessary.
16. Secure the pulley to the motor by tightening the
pulley setscrew to the motor shaft.
17. Insert four bolts and flat washers through mounting
holes on the motor into holes on the motor mounting
plate.
18. On one bolt, place a new external--tooth lock washer
betwee n the motor and motor mounting band.
19. Ensure the teeth of the external--tooth lock washer
make c ontact with the painted base of the motor.
This washer is essentia l for properly grounding motor.
20. Install four new lock washers and four nuts on the
bolts on the bottom of the motor mounting plate.
21. Do Not tighten the mounting bolts at this time.
22. Set new motor and motor mounting bracket back onto
the unit. See Fig. 15.
23. Install four bolts, four flat washers, four new lock
washers and four nuts attaching the motor assembly
to the unit.
24. Do Not tighten the mounting bolts at this time.
25. Install motor drive V--belt to motor pulley and blower
wheel pulley. See CAUTION.
26. Align the motor pulley and blower wheel pulley using
a straight edge. See Fig. 10.
27. Adjust the V--belt tension using adjustment tool.
28. Turn two jack bolts clockwise, moving the motor
assembly away from the blower pulley, increasing the
V--belt tension.
29. Tighten the four bolts securing the motor mount ing
bracke ts to the unit. Torque four bolts to 120 12
in--lbs (14 1.4 Nm).
30. Remove cover on motor connecti on box.
31. Re--connect all electrical leads to the motor and
repla ce the connect ion box cover.
32. Re--connect all electrical power to the unit. Remove
lockout tags on a ll electrical power sources.
33. Start unit and allow to run for a designated period.
34. Shut off unit and make any necessary adjustments to
the V--belt tension or the motor and blower wheel
pulley alignment.
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--lbs.
Changing Fan Wheel Speed
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 diameter to
increase wheel speed) or select a new system (both
pulleys and matching belt).
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
capa ble of operating at the new operating condition. Fan
shaft loading increases dramatically as wheel speed is
increased.
To reduce vibration, replace the motor’s adjustable pit ch
pulley with a fixed pitch pulley (after the final airflow
bala nce adjustment). This will reduce the amount of
vibration generated by the motor/belt--drive system.
48HC
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