Page 239 - HVAC Pump Handbook

Rishel_CH08.qxd 21/4/06 6:16 PM Page 236

The Use of Water in HVAC Systems

236 The HVAC World

DP
Building coils with
control valves

C Crossover bridge
Building pump
Return valve loss
is equal to hydraulic
gradient of system

96'
Chiller

Variable C
primary
pump

Figure 8.9 Energy waste of crossover bridges on variable speed systems.
(From Patterson Pump Company, HVAC Pumps and Systems Manual, 2004.)

8.7 Categorization of HVAC Water Systems
HVAC water systems can be categorized by whether they are open or
closed. Any classification will create some confusion, but these cate-
gories should be adequate for evaluating pumps on all HVAC water
systems.
Open systems have no external pressures placed on them, and usu-
ally, they include an open tank holding a reservoir of water. Water
makeup is made to these systems at the reservoir or tank. Following
is a listing of open-type systems and chapter of this book that
describes them.

Cooling tower pumps Chap. 11
Pumps for process cooling Chap. 12
Open thermal storage systems Chap. 13

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.