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TRG-TRC016-EN 41
period two
Chilled-Water System Design
notes
Primary-Secondary (Decoupled) Configuration
If the water flow through the chillers (production) could be hydraulically
isolated from the water flow through the coils (distribution), many of the
problems encountered in parallel and series configurations could be
eliminated.
Figure 47 shows a configuration that separates, or “decouples,” the production
capacity from the distribution load. This scheme is known as a primary-
secondary system, also referred to as a decoupled system. This
configuration is unique because it dedicates separate pumps to the
“production” and “distribution” loops. A bypass pipe that connects the supply
and return pipes is the key component in decoupling the system.
The chillers in the production loop receive a constant flow of water, while the
coils in the distribution loop, controlled by two-way modulating valves, receive
a variable flow of water.
Primary-Secondary Configuration
production
production
pumps
pumps
two
two
-
-
way valve
way valve
distribution
distribution
pump
pump
distribution
distribution
loop
loop
production
production
loop
loop
b
y
p
a
s
s
p
i
p
e
b
y
p
a
s
s
p
i
p
e
Figure 47