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TRG-TRC016-EN 29
period two
Chilled-Water System Design
notes
A three-way control valve is one method used to regulate the flow of chilled
water through a cooling coil. As the space cooling load decreases, the
modulating valve directs less water through the coil, decreasing its capacity.
The excess water bypasses the coil and mixes downstream with the water that
flows through the coil. As a result, the temperature of the water returning from
the system decreases as the space cooling load decreases.
Systems that use three-way valves have the following characteristics:
n The temperature of the water returning from the system varies as the
cooling load varies.
n The water flow through each load terminal (water through the coil plus
water bypassing the coil) is relatively constant at all load conditions.
n The pump energy is constant at all loads because the use of three-way
valves results in constant water flow throughout the system.
n Water-flow balance is very critical to proper operation because the flow
is constant.
Three-Way Valve Control
three
three
-
-
way
way
modul ati ng
modulating
valve
valve
airflow
airflow
bypass
bypass
pipe
pipe
Figure 34