20 McQuay IM 777-4
Operation Guidelines
Figure 32: Torque for FC Variable Inlet Vanes (in–lb)
Figure 33: Torque for AF Variable Inlet Vanes (in–lb)
Table 9: Unit Sizes 040 to 090
Fan operating limits
Forward curved—housed
Diameter 20 22.38 25 27.62 30.25 33 36
Maximum rpm Class I 1010 930 790 690 650 600 560
Maximum rpm Class Il 1281 1178 1011 910 835 763 715
Airfoil—housed
Diameter 20 22.25 24.5 27 30 33 36.5
Maximum rpm Class I 2077 1875 1691 1479 1328 1209 1073
Maximum rpm Class Il 2703 2413 2199 1928 1730 1579 1401
300
250
200
150
100
90
80
70
60
50
350
400
450
500
550
600
650
700
750
800
850
900
1000
1500
2000
Fan speed (rpm)
FC22.25
FC20.00
FC18.00
FC15.00
FC12.62
FC24.50
Torque (in–lb)
300
250
200
150
100
600
650
700
750
800
850
1000
Fan speed (rpm)
900
400
350
550
900
AF40.25
AF27.00
AF24.50
AF22.25
AF20.00
AF38.50
AF33.00
AF30.00
500
600
700
800
2000
1000
1500
1500
2000
3000
2500
Torque (in–lb)
Table 10: 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
Maximum rpm Class I 2895 2589 2376 2256 2077 1875 1691 1479 1328 1209 1073 972 882 799 725 651
Maximum rpm Class II 3786 3384 3100 2959 2703 2413 2199 1928 1730 1579 1401 1264 1150 1043 938 847
Maximum rpm Class III 4000 4000 3887 3735 3409 3065 2780 2423 2182 1984 1756 1598 1447 1314 1178 1071
Table 11: 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