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Basics of Pump Application for HVAC Systems

Basics of Pump Application for HVAC Systems 295

project discussed earlier, and the pump curve is shown in Fig. 10.10b.
Only one pump runs at a time.

10.8.2 Wire-to-water efficiency for three pumps
The wire-to-water efficiency for the three-pump system for the hospi-
tal discussed earlier is listed in Table 10.5, and the pump curve is
described in Fig. 10.10c. One or two pumps run depending on the wire-
to-water efficiency.

TABLE 10.5 Wire-to-Water Efficiencies for Three 50 Percent System 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
One pump running
0500 23.6 3.0 1.6 25.2 845 84.6 3.3 66.3*
0625 25.0 4.0 2.5 27.9 927 86.8 4.4 67.7*
0750 27.0 5.2 3.6 31.1 1012 87.3 5.8 67.2*
0875 30.0 6.6 4.9 34.9 1104 86.8 7.5 65.7*
1000 32.9 8.3 6.4 39.3 1201 85.9 9.7 63.7
1125 36.0 10.2 8.1 44.1 1302 85.0 12.4 61.7
1250 39.4 12.4 10.0 49.4 1406 84.0 15.5 59.9
1375 43.2 15.0 12.1 55.3 1511 83.0 19.2 58.2
1500 47.2 17.9 14.4 61.6 1619 82.1 23.6 56.6
1625 51.5 21.2 16.9 68.4 1728 81.3 28.7 55.1
1685 53.7 22.9 18.2 71.9 1780 81.0 31.4 54.3
Two pumps running
0875 30.0 6.6 1.2 31.3 924 78.2 7.7 64.4
1000 32.9 8.3 1.6 34.5 978 80.7 9.3 66.7*
1125 36.0 10.2 2.0 38.0 1035 82.5 11.2 68.2*
1375 43.2 15.0 3.0 46.2 1158 84.7 16.0 69.9*
1500 47.2 17.9 3.6 50.8 1222 85.4 19.0 70.4*
1625 51.5 21.2 4.2 55.8 1289 85.9 22.3 70.6*
1750 56.2 24.8 4.9 61.1 1356 86.3 26.2 70.8*
1875 61.1 28.9 5.6 66.7 1425 86.5 30.5 70.9*
2000 66.3 33.5 6.4 72.7 1494 86.7 35.2 70.9*
2125 71.8 38.5 7.2 79.0 1565 86.0 40.5 70.9*
2250 77.6 44.1 8.1 85.7 1636 87.0 46.4 70.9*
2375 83.7 50.2 9.0 92.7 1707 87.1 52.9 70.7*
2500 90.0 56.8 10.0 100.0 1779 87.1 60.3 70.3*
NOTE: Pump and wire-to-water efficiencies are in percent.
*Denotes most efficient operation and correct number of pumps to operate at each sys-
tem gallons per minute.

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