5
Adjustable--Pitch Pulley on Motor
The motor pulley is an adjustable--pitch type that allows a
servicer to implement changes in the fan wheel speed to match
as--installed ductwork systems. The pulley consists of a fixed
flange side that faces the motor (secured to the motor shaft) and
a movable flange side that can be rotated around the fixed
flange side that increases or reduces the pitch diameter of this
driver pulley. (See Fig. 6.)
As the pitch diameter is changed by adjusting the position of the
movable flange, the centerline on this pulley shifts laterally
(along the motor shaft). This creates a requirement for a
realignment of the pulleys after any adjustment of the movable
flange. Also reset the belt tension after each realignment.
Check the condition of the motor pulley for signs of wear .
Glazing of the belt contact surfaces and erosion on these
surfaces are signs of improper belt tension and/or belt slippage.
Pulley replacement may be necessary.
To change fan speed:
1. Shut off unit power supply.
2. Loosen belt by loosening fan motor mounting nuts. (See
Fig. 5.)
3. Loosen movable pulley flange setscrew. (See Fig. 6.)
4. Screw movable flange toward fixed flange to increase
speed and away from fixed flange to decrease speed. In-
creasing fan speed increases load on motor. Do not exceed
maximum speed specified.
5. Set movable flange at nearest keyway of pulley hub and
tighten setscrew to torque specifications.
To align fan and motor pulleys:
1. Loosen fan pulley setscrews.
2. Slide fan pulley along fan shaft. Make angular alignment
by loosening motor from mounting.
3. Tighten fan pulley setscrews and motor mounting bolts to
torque specifications.
4. Recheck belt tension.
FIGURE 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
capscrewto65--70in--lb(7.4--7.9Nm).SeeFig.7.
FIGURE 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--lbs.
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(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 condition. 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
adjustment). This will reduce the amount of vibration generated
by the motor/belt--drive system.
COOLING
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 pressures than R--22 and other refrigerants. No
other refrigerant may be used in this system. Gauge
set, hoses, and recovery system must be designed to
handle R--410A refrigerant. If unsure about
equipment, consult the equipment manufacturer.
!
WARNING