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TRG-TRC016-EN 53
period two
Chilled-Water System Design
notes
Primary-Secondary System Operation
We have seen that the production and distribution loops of the primary-
secondary system act independently. The next consideration is to match the
capacity of the production loop to the load of the distribution loop. The
operation of a primary-secondary system focuses on the direction and
amount of flow in the bypass line.
At the supply tee, which connects the supply and bypass pipes, a supply-and-
demand relationship exists. The total water flow from all operating production
(chiller) pumps is the “supply” flow. The “demand” flow is the total water flow
required to meet the loads on the cooling coils. Whenever the supply and
demand flows are unequal, water will either flow into, or out of, the bypass
pipe at the supply tee.
System Operation
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
return
return
tee
tee
supply
supply
tee
tee
s
u
p
p
l
y
s
u
p
p
l
y
f
l
o
w
f
l
o
w
d
e
m
a
n
d
d
e
m
a
n
d
f
l
o
w
f
l
o
w
Figure 59