Unit installation
McQuay IM 777 21
Operation Guidelines
Figure 35: Torque Requirements at 100% WOV for
SWSI Plenum Fans with NESTED Inlet Vane
Fan Vibration Levels
Each unit as shipped is trim balanced to operate smoothly. To
provide satisfactory operation after shipping and installation,
use the accepted industry guidelines for field balancing fans.
See Table 14.
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.
Vibration Causes
1 Wheel imbalance.
a Dirt or debris on wheel blades.
b Loose set screws in wheel hub or bearing-to-shaft.
c Wheel distorted from overspeed.
2 Bent shaft.
3 Drive faulty.
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
Table 12: Operating Limits—Plenum Fans
Fan operating limits
Plenum fans
Diameter 13.5 15 16.5 18.25 20 22.25 24.5 27 30 33 36.5 40.25 44.50 49 54.25 60
Class 2222222222222222
Maximum rpm 3,909 3,468 2,820 2,930 2,674 2,403 2,183 1,860 1,783 1,620 1,465 1,329 1,202 1,091 986 891
Maximum motor HP 7.5101515152025304040506075757575
Table 13: Operating Limits—Inline Fans, Twin Fans
Fan operating limits
Inline fans
Diameter 18.25 20 22.25 24.5 27 30 33 36.5 40.25 44.50 49 54.25
Maximum rpm Class I 2727 2488 2236 2041 1835 1665 1476 1330 1208 1072 973 880
Maximum rpm Class II 3409 3111 2796 2551 2294 2082 1846 1662 1510 1340 1216 1100
Twin fans
Diameter 9 x 9 10.62 12.62 15 18.12 20
Maximum rpm 2575 2400 2000 1700 1400 1200
Maximum HP 10 15 15 30 40 40
6
0
0
700
600
500
400
100
900
300
200
Torque (lb./in.)
Fan Speed (rpm)
800
900
1000
1500
2000
400
500
600
700
300
200
3000
800
1000
2000
3000
4000
5000
5
4
2
4
9
0
4
4
5
4
0
2
3
6
5
3
3
0
3
0
0
2
7
0
2
4
5
Torque (in-lb)
Table 14: Vibration Levels
Fan speed (rpm) Vibration
800 or less 5 mils maximum displacement
801 or greater 0.20 in/sec. maximum velocity