4
To replace the belt:
1. Use a belt with same section type or similar size. Do not
substitute a “FHP” type belt. When installing the new belt,
do not use a tool (screwdriver or pry-bar) to force the belt
over the pulley flanges. This will stress the belt and cause
a reduction in belt life.
2. Loosen the motor mounting plate front bolts and rear
bolts.
3. Loosen the Jack bolt lock nuts and using the Jack bolts
relieve the belt tension to allow easy removal of the belt
by hand.
4. Remove the belt by gently lifting the old belt over one of
the pulleys.
5. Install the new belt by gently sliding the belt over both
pulleys, then using the Jack bolts slide the motor plate
away from the fan housing until proper belt tension is
achieved.
6. Check the alignment of the pulleys; adjust if necessary.
7. Tighten all nuts to motor plate and Jack bolts.
8. Check the tension after a few hours of runtime and re-
adjust as required.
ADJUSTABLE-PITCH PULLEY ON MOTOR
The motor pulley is an adjustable-pitch type that allows a ser-
vicer 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.)
Fig. 6 — Supply-Fan Pulley Adjustment
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 re-
alignment 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 sur-
faces 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 and install lock-out tag.
2. Loosen belt by loosening the motor adjustment bolts as
described in the Belt Adjustment section above. (See
Fig. 4.)
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.
Increasing fan speed increases load on motor. Do not
exceed maximum speed listed in the Product Data or
motor amperage as listed on the unit rating plate.
5. Set movable flange at nearest keyway or flat of pulley hub
and tighten setscrew to torque specifications. Torque pul-
ley set screw to 72 ± 5 (in. lbs).
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.
BEARINGS
This fan system uses bearings featuring concentric split lock-
ing 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 — 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 bite through and 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 (typi-
cally the motor pulley in these units). Do not install a replace-
ment motor pulley with a smaller pitch diameter than provided
on the original factory pulley. Change fan wheel speed by
changing the fixed sheave 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 deter-
mine new motor loading (bhp). Use the fan performance tables
or use the Packaged Rooftop Builder software program. Con-
firm that the motor in this unit is capable of operating at the
new operating condition. Fan shaft loading increases dramati-
cally 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-
ment). This will reduce the amount of vibration generated by
the motor/belt-drive system. To determine variable pitch pulley
diameter perform the following calculation:
1. Determine full open and full closed pulley diameter.
2. Subtract the full open diameter from the full closed diameter.
STRAIGHT EDGE
MUST BE PARALLEL
WITH BELT
SETSCREWS
MOTOR AND
FANSHAFTS
MUST BE
PARALLEL
FIXED FLANGE
MOVABLE
FLANGE
SINGLE - GROOVE
FAN PULLEY
MOTOR PULLEY
T --- 25 TORX SOCKET
HEAD CAP SCREW
LOCKING COLLAR
Summary of Contents for 50LC 14
Page 26: ...26 Fig 34 50LC 14 26 Control Wiring Diagram...
Page 27: ...27 Fig 35 50LC 14 26 RTU Open Control Wiring Diagram...
Page 28: ...28 Fig 36 50LC 14 20 208 230V 3 Phase Power Wiring Diagram...
Page 29: ...29 Fig 37 50LC 24 26 208 230V 3 Phase Power Wiring Diagram...
Page 30: ...30 Fig 38 50LC 14 26 460V 575V 3 Phase Power Wiring Diagram...