25
Fig. 21 — Fan Shaft, Bearings, and Fan Wheel (Typical)
Centering Fan Wheel
If fan and fan shaft assembly are not properly centered, blades
may scrape against the blower side scroll plate or may create
an objectionable whistling noise. It may be necessary to adjust
individual fan wheels or move entire fan shaft. See the follow
-
ing 2 sections.
Individual Fan Wheel Adjustment
Loosen the 2 locking bolts holding the fan wheel hub to shaft.
(See Fig. 21.) Position fan wheel in center of the fan housing
and tighten locking bolts. Clearance between wheel and hous
-
ing should be the same on both sides.
Fan Shaft Position Adjustment
Loosen setscrew or locking collar of each fan shaft bearing.
Slide shaft into correct position and replace locking collar. (See
Fig. 22). To replace locking collar, push collar up against inner
face of bearing. Turn collar in direction of fan rotation until
tight, and tighten setscrew. Tightening locking collar in direc
-
tion of fan rotation results in further tightening of collar should
setscrew work itself loose.
Fig. 22 — Fan Shaft Bearing
Fan Belts
Motor mounting plate and motor support angles are slotted to
permit both vertical and horizontal adjustment. Adjust belt(s)
for correct deflection by loosening motor plate mounting bolts,
moving motor/plate assembly forward or back, and re-
tightening bolts. Press down on belt with one finger midway
between fan and motor pulleys to check deflection. For units
with motor sizes up to and including 3.7 Hp (2.76 kW), correct
deflection is 3/16 in. (4.8 mm). For larger motor sizes, correct
deflection is 1/8 in. (3.2 mm). (See Fig. 23.)
If complete belt replacement is required during servicing, loos
-
en the motor plate mounting bolts (Fig. 23), move motor/plate
assembly towards fan pulley, and pull belt(s) off pulleys.
Reverse the procedure with new bolts and readjust deflection.
Fan Rotation
Correct fan rotation with respect to fan outlet is shown in
Fig. 24.
To reverse the direction of rotation of a 3-phase fan motor,
reverse any 2 of the power leads. Refer to the connection
diagram on the inside of motor terminal box cover for proper
reversing procedure of a single-phase motor.
Fig. 23 — Fan Motor Mounting
