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www.DaikinApplied.com 131
IM 893-10 • ROOFPAK SINGLEZONE UNITS
Propeller Exhaust Fan
Propeller Exhaust Fan Option on page 87
Vibration Levels
Each unit as shipped is trim balanced to operate smoothly. To
provide satisfactory operation after shipping and installation,
use accepted industry guidelines for field balancing fans. See
NOTE:
Excessive vibration from any cause contributes to
premature fan and motor bearing failure. Monitor overall
vibration levels every six months of operation. An
increase in levels is an indication of potential trouble.
Table 29: Vibration Levels
Fan speed (RPM)
Vibration
800 or less
5 mils maximum displacement
801 or greater
0.20 in/sec maximum velocity
Vibration Causes
1. Wheel imbalance.
a. Dirt or debris on wheel blades.
b. Loose setscrews in wheel hub.
c. Wheel distorted from overspeed.
2. Bent shaft.
3. Faulty drive.
a. Variable pitch sheaves—Axial and radial runout of
flanges; uneven groove spacing; out of balance.
Also similar faults in driven sheave.
b. Bad V-belts; lumpy, or mismatched; belt tension
too tight or too loose.
4. Bad bearings, loose bearing hold-down bolts.
5. Motor imbalance.
6. Fan section not supported evenly on foundation.
Periodic Service and Maintenance
1. Check all moving parts for wear every six months.
2. Check bearing collar, sheave, and wheel hub setscrews,
sheave capscrews, and bearing hold-down bolts for
tightness every six months.
Setscrews
Setscrews are used to lock sheaves, locking collars, and fan
wheels to their shafts. They must be checked periodically to
see that they have not loosened. If this is not done, severe
equipment damage could occur.
Using
, check the tightness of all setscrews with a
torque wrench. Note that if the return fan bearings setscrews
must be retightened, a special procedure is required to equally
load both bearings (see “Return Fan Bearing Setscrews” ).
Table 30: Setscrew Minimum Torque Specifications
Setscrew diameter (in .)
Minimum torque (ft .lb)
1/4
5.5
5/16
10.5
3/8
19.0
7/16
29.0
1/2
42.0
5/8
92.0
Return Fan Bearing Setscrews
IMPORTANT
To maintain proper drive alignment and fan-to-tunnel
clearance, the fan and shaft must not drop at all when the
setscrews are loosened in Step 4.
Because the return fan is mounted on a vertical shaft, the
following procedure must be used to retighten any return fan
bearing setscrews that have loosened. This procedure will
provide that both bearings are equally loaded. If one bearing is
carrying the entire weight of the fan, it could fail prematurely.
1. Loosen the fan belts.
2. Support the weight of the fan and the fan shaft with
timbers or some other suitable means (see the fan shaft
support in
).
3. Verify that the upper shaft collar is securely fastened to
the shaft. Check the setscrew torque.
4. Loosen the upper and lower bearing setscrews. The
entire weight of the fan and shaft is now supported by
the fan shaft support.
5. Retighten all bearings to the torque specification given
in
. Remove the fan shaft support and retension
the belts.
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