92
McQuay IM 987
Unit Options
Belts
Premature belt failures are frequently caused by improper belt
tension (either too tight or too loose) or misaligned pulleys.
The proper tension for operating a V-belt is the lowest tension
at which the belts will not slip peak load conditions. For initial
tensioning, the proper belt deflection half way between pulley
centers is 1/64" for each inch of belt span. For example, if the
belt span is 64 inches, the belt deflection should be one inch
using moderate thumb pressure at midpoint of the drive
(see
Figure 106
).
Check belt tension two times during the first 24 hours of
operation and periodically thereafter. To adjust belt tension,
simply loosen four fasteners (two on each side of the motor
plate) and slide the motor plate away from the fan shaft until
proper belt tension is attained. On some fans, fasteners
attaching the motor to the motor plate must be loosened to
adjust the belt.
It is very important that the drive pulleys remain in proper
alignment after adjustments are made (see
Figure 107
).
Misalignment of pulleys results in premature belt wear noise,
vibration, and power loss.
Figure 106: Belt Adjustment
Figure 107: Drive Pulley Alignment
Figure 108: Propeller Exhaust Fan Replacement Parts List
WARNING
Rotating parts can cause severe personal injury or death.
Replace all belt/fan guards that are removed temporarily for
service.
B e l t S p a n
D e f l e c t i o n = B e l t S p a n
6 4
C e n t e r l i n e s
m u s t c o i n c i d e
M u s t b e
p a r a l l e l
M u s t b e
p a r a l l e l
A d j u s t a b l e
S h e a v e
M o t o r
B e a r i n g
9
8
7
1 0
6
5
4
1
2
3
1 . F a n P a n e l
2 . P r o p e l l e r
3 . D r i v e F r a m e
C h a n n e l ( 2 )
4 . M o t o r P l a t e
5 . M o t o r
6 . M o t o r P u l l e y
7 . S h a f t P u l l e y
8 . F a n S h a f t
9 . B e a r i n g s
1 0 . B e l t
1 1 . B e a r i n g P l a t e
