Filter
Top Products
56 TRG-TRC016-EN
notes
period two
Chilled-Water System Design
Starting and stopping of pump-and-chiller pairs in a primary-secondary system
depends on the direction and quantity of water flow in the bypass pipe.
n Whenever there is deficit flow through the bypass pipe for a specified period
of time (typically 15 to 30 minutes in a comfort-cooling system), another
pump-and-chiller pair started.
n Whenever there is excess flow through the bypass pipe that is greater than
the flow being produced by the next pump-and-chiller pair to be turned off,
that pump and chiller are turned off. To prevent short cycling as the result of
a slight increase in load, the chiller-plant control system will typically allow
excess flow of from 110 to 115 percent of the flow produced by the next
production pump to be turned off.
n If neither of the above conditions exist, no action is taken.
Control of Primary-Secondary System
condition
deficit flow for
specified period of
time
excess flow greater
than 110% to 115% of
next pump to turn off
neither
condition
deficit flow for
specified period of
time
excess flow greater
than 110% to 115% of
next pump to turn off
neither
response
start another
chiller and pump
turn off next chiller
and pump
do nothing
response
start another
chiller and pump
turn off next chiller
and pump
do nothing
Figure 62