Carrier 50TCQD17-D24 Service And Maintenance Instructions page 5

1. Loosen the four front and rear motor mounting plate
bolts.
2. Loosen the two jack bolt jam nuts.
3. Turn the two jack bolts counterclockwise to loosen
bringing the motor closer to the blower.
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. and then sliding the motor and plate
away from the fan housing until proper tension is
achieved.
Fig. 6 - - Replacing the V- - Belt
6. Turn the jack bolts clockwise to increase the tension
of the V- - belt.
7. Adjust the V- - belt tension using Browning's "Belt
Tension Checker" (p/n 1302546 or equivalent tool) to
6- - lbs at a ⅝- - in (1.6 cm) deflection when measured at
the centerline of the belt span. The tension can also
be checked depressing the belt at mid- - span with one
finger until a ½- - in (1.3 cm) deflection is reached.
8. Check alignment of the pulleys, adjust the motor
mounting base as needed. Tighten four motor mounting
bolts. Torque all bolts to 65- - 70 in- - lb (7.4 to 7.9 Nm).
9. Tighten two jack bolt jam nuts. Torque jam nuts to
65- - 70 in- - lb (7.4 to 7.9 Nm).
10. 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
servicer to implement changes in the fan wheel speed to
match previously 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. 7.
BLOWER PULLEY
V-BELT
MOTOR PULLEY
MOTOR
MOTOR MOUNTING
BOLTS (4)
JACK BOLT
JAM NUT (2)
JACK BOLT (2)
C12034
Fig. 7 - - 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 realignment of the pulleys after any
adjustment of the movable flange. 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. Replace pulley if necessary.
Changing the Fan Speed:
1. Shut off unit power supply. Use proper Lockout/
Tagout procedures.
2. Loosen belt by loosening fan motor mounting nuts.
See Fig. 7.
3. Loosen movable pulley flange setscrew. See Fig. 7.
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 the maximum specified speed.
5. Set movable flange at nearest keyway of pulley hub.
Tighten setscrew and torque to 65- - 70 in- - lb (7.4 to 7.9
Nm).
Aligning Fan and Motor Pulleys:
1. Loosen fan pulley setscrews.
2. Slide fan pulley along fan shaft. Make angular align-
ment by loosening motor mounting plate front and
rear bolts.
3. Tighten fan pulley setscrews and motor mounting
bolts and torque to 65- - 70 in- - lb (7.4 to 7.9 Nm).
4. Recheck belt tension.
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C07075