Page 154 - HVAC Pump Handbook

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HVAC Pump Performance

HVAC Pump Performance 151

1780. A system head curve is shown with a static head of 26 ft and a
friction head of 34 ft for a total head of 60 ft. A discussion of system
head curves will be included in Chap. 10. These typical multiple pump
curves are for three pumps operating at a constant speed or full speed
for variable-speed pumps. What happens when the pumps become
variable speed?
Figure 6.10 is a pump operating area for one variable speed pump
while Fig. 6.11 is for two pumps, and Fig. 6.12 is for three pumps.

90

60%
80
75%

70 85%
Best
88% efficiency
area
System and pump head—ft. 50 85% 75%
60
88%

40

30

20
968 RPM

10

0
0 1000 2000 3000
System flow—GPM
Figure 6.10 Single pump performance under variable speed.

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