Page 305 - HVAC Pump Handbook

Rishel_CH10.qxd 21/4/06 6:20 PM Page 302

Basics of Pump Application for HVAC Systems

302 The HVAC World

160

100% Capacity
pump
140
60% Possible 75%
50%
70% capacity pump
70%
80%
120 80%
86%
84%
50% Capacity
pump 86% 89%
100 Efficiency is

Pump head—ft. 80 86.5% at 1500 GPM

Efficiency is
89.2% at 3000 GPM

60
System head curve
for one 50%
capacity pump
System head curve
40 for two 50% or one
100% capacity pumps

20

0
0 500 1000 1500 2000 2500 3000
System flow—GPM
Figure 10.15 Percent head-flow and system head curves.

A third computation was run with all three pumps in operation.
There were no energy savings for this system with all three pumps
running, so the calculations were not included. Such is not the case
with many three-pump systems where operating all three pumps,
save energy at the highest flows in the water system.
The data of Tables 10.8, 10.9, and 10.10 demonstrates the advan-
tages of each of the three installations. A summary of the kW inputs
is shown graphically in Fig. 10.16. This indicates the following:

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