Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual page 177

4. Check tightness of fan-shaft bearing mounting. See
Fig. 156.
5. Recheck sheave alignment and belt tension. (Refer to
Fig. 47 and 48.)
6. Hand turn fan to make certain fan wheel does not rub
in housing.
7. Check fan speed with a strobe-type tachometer or use
the following formula:
Obtain the motor rpm from the fan motor nameplate
and read sheave pitch diameters marked on the fan and
motor pulleys, or approximate the pitch diameters by
using the pulley ODs.
Then:
Motor Rpm x Motor Sheave
Pitch Diameter (in.)
Fan RPM =
Fan Sheave Pitch Diameter (in.)
EXAMPLE:
Nameplate Motor
=
RPM
Motor Sheave Pitch
=
Diameter
Fan Sheave Pitch
=
Diameter
Fan RPM =
=
Refer to Table 6 for maximum allowable fan speeds
for fan wheels. Excessive fan speed may result in con-
densate carryover from cooling coil or fan motor over-
load and wheel failure.
8. Check direction of rotation (see Table 35). Arrow on
drive side of fan housing indicates correct direction of
rotation.
IMPORTANT: Drive ratios of 1:1 may cause excessive
vibration. Avoid if possible.
9. Check vibration. If excessive vibration occurs, check
for the following:
a. Variable sheave (if air balance of system has been
accomplished; replace sheave with fixed sheave
for continuous application).
b. Drive misalignment.
c. Mismatched, worn, or loose belts.
d. Wheel or sheaves loose on shaft.
e. Loose bearings.
f. Loose mounting bolts.
g. Motor out of balance.
h. Sheaves eccentric or out of balance.
i. Vibration isolators improperly adjusted.
j. Out-of-balance or corroded wheel (rebalance or
replace if necessary).
k. Accumulation of material on wheel (remove
excess material).
ACTUAL APPROXIMATE
1760 1760
8.9 9.0 (OD)
12.4 12.5 (OD)
1760 x 8.9 1760 x 9.0
12.4 12.5
1263 RPM = 1267 RPM
DRIVE PULLEY
NOMINAL
SCREW SIZE
NO. 6
NO. 8
NO. 10
1 /
4
5
/
16
3 /
8
Fig. 155 — Fan, Shaft and Bearing Details —
Roller — Extended Race, One or Both Sides
TORQUE TABLE
CAPSCREW AND
SETSCREW
SIZE (NO./in.)
10
1
/
4
5
/
16
3 /
8
7 /
16
1
/
2
5 /
8
3 /
4
BEARING HOLDDOWN BOLT TORQUE
BOLT SIZE (in.) TORQUE (ft-lb)
3 / - 16
8
1 / - 13
2
5
/ - 11
8
3
/ - 10
4
Fig. 156 — Fan, Shaft and Bearing Details —
Squeeze-Type Locking Collar
177
TORQUE
(in.-lb)
9
16
30
70
140
216
HEX HEAD SQUARE HD
ACROSS ACROSS
FLATS (in.) FLATS (in.)
3 / —
32
1
/ —
8
5
/ —
32
3 / —
16
7 / —
32
1 1
/ /
4 2
5 / —
16
3 / —
8
30
63
100
165
TORQUE
25 in.-lb
60 in.-lb
10 ft-lb
17 ft-lb
25 ft-lb
40 ft-lb
90 ft-lb
125 ft-lb