Page 297 - HVAC Pump Handbook

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Basics of Pump Application for HVAC Systems

294 The HVAC World

TABLE 10.3 Typical Wire-to-Shaft Efficiencies for Variable-Speed Drives with
High-Efficiency Motors

Motor horsepower
Percent
full load 15 50 75 100 150 200
000 0 0 0 0 0 0
040 50.2 63.0 61.5 59.2 67.2 67.0
060 73.2 81.3 80.5 79.6 84.4 84.7
080 84.4 88.3 88.3 88.6 90.9 90.6
090 86.5 89.8 90.9 91.0 91.8 91.8
100 87.7 90.9 91.4 92.2 92.9 93.1

the drive manufacturer from calculations and tests of various motor
and drive combinations. It cannot be just a multiplication of the motor
and drive efficiencies. All variable-frequency drives notch or disturb
the sine wave, which affects the efficiency of the motor.
Typical wire-to-shaft efficiencies for high-efficiency motors and
variable-speed drives from 10 through 200 hp are shown in Table 10.3.
Actual wire-to-shaft efficiencies for a specific application should be
secured from the variable-speed drive manufacturer after receipt of
information on the proposed pump motor.

10.8.1 Wire-to-water efficiency for two pumps
An example of this wire-to-water efficiency program is given in
Table 10.4. This table is for the two-pump system for the hospital

TABLE 10.4 Wire-to-Water Efficiency Calculations for Two 100 Percent Capacity Pumps

System System Water Fitting Pump Pump Pump Input W/W
gal/min head, ft hp loss, ft head, ft rev/min efficiency kW efficiency
0500 23.6 3.0 0.4 24.0 723 67.0 4.8 45.9
0625 25.4 4.0 0.6 26.0 771 73.1 5.8 51.2
0750 27.5 5.2 0.9 28.4 827 77.0 7.1 55.2
1000 32.9 8.0 1.6 34.5 947 81.3 10.2 60.6
1250 39.4 12.4 2.5 41.9 1071 83.3 14.5 63.9
1500 47.2 17.9 3.6 50.8 1204 84.2 20.2 65.9
1625 51.5 21.2 4.2 55.8 1273 84.4 23.7 66.7
1750 56.2 24.8 4.9 61.1 1343 84.5 27.5 67.2
1875 61.1 28.9 5.6 66.7 1414 84.5 31.9 67.7
2000 66.3 33.5 6.4 72.7 1486 84.6 36.8 68.0
2125 71.8 38.5 7.2 79.0 1559 84.5 42.2 68.1
2250 77.6 44.1 8.1 85.7 1632 84.5 48.3 68.1
2375 83.7 50.2 9.0 92.7 1706 84.5 55.0 68.1
2500 90.0 56.8 10.0 100.0 1780 84.4 62.6 67.7
NOTE: Pump and wire-to-water efficiencies are in percent.

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