Page 265 - HVAC Pump Handbook

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Configuring an HVAC Water System

262 The HVAC World

This will be explained further in this book with other design criteria
for this important method of water distribution.

9.5 Three Zones of HVAC Water Systems
Almost all HVAC water systems are of the loop type; this means that
the water is returned to its source such as a chiller, cooling tower, or
boiler. In rare cases, groundwater is used for cooling and is dumped
into a sewer or stream after use.
Most of these water systems consist of three zones, namely, (1) an
energy source, (2) energy transportation, and (3) energy use as
described in Fig. 8.4 for chilled or hot water. Cooling towers are simi-
lar in arrangement. Chapter 8 discussed the use of water, or the third
zone. It is important to understand that each of these three zones
must be designed individually for optimal use of energy. Therefore,
these zones often are combined together with resulting poor energy
generation, transportation, or use. Each zone must be evaluated sepa-
rately; the first and second zones will be reviewed in the chapters on
chillers and boilers. True energy conservation in HVAC systems
begins with careful analysis of energy consumption in boilers, chillers,
or cooling towers. Chapters 11, 14, and 19 of this book will study this
analysis of energy consumption.
Many times the second zone, energy transportation, is mixed with
energy generation; this can result in poor energy generation and
transportation if care is not used in evaluating the total energy con-
sumption of the system. Efficient energy transportation will be dis-
cussed in Chaps. 15, 16, 18, and 20 on cooling and heating systems.
Finally, the use of water in cooling and heating coils or heat
exchangers must be efficient or pumping costs will be excessive. As
indicated in Chap. 8, the indiscriminate use of balance valves, three-
way control valves, and improper heating and cooling coil connections
results in poor system efficiency. If these three zones are remembered
during design and each treated as efficiently as possible, this effort
should result in a good pumping and piping system.

9.6 Piping Configurations
A number of different piping configurations are used in HVAC water
systems; only the more popular types will be discussed here. These are:
1. Open or closed systems and how water is returned to the source,
namely, direct or reverse return
2. Number of pipes to transport the water through the system

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