TRG-TRC010-EN 39
period five
Application Considerations
notes
Constant or Variable Evaporator Water Flow
Previous chiller designs required that a constant flow rate of water be
maintained through the evaporator. This requirement has changed due to
advances in chiller controls. Increased sensing and control capabilities now
allow chiller manufacturers to design controls that monitor, and respond faster
to, fluctuating conditions.
While the chiller may be able to handle variable water flow through the
evaporator, the specific application of the chilled water system may not warrant
variable flow. As always, each application should be analyzed to determine if
variable evaporator water flow is warranted.
The controls on many current chiller designs can properly control the chiller in
response to varying evaporator flow rates, with the following limitations:
evaporator water flow
Constant or Variable Flow
variable-
variable-
speed
speed
drive
drive
chilled
chilled
water
water
pump
pump
evaporator
evaporator
Figure 54
variable evaporator water flow
Limitations
▲ Maintain minimum and maximum water flow
rates through the chiller evaporator
▲ Rate at which the evaporator water flow
changes must be kept below the
corresponding limit to:
◆ Maintain the chilled water set point control
◆ Keep the chiller on line
◆ Protect the chiller from damage
Figure 55
trgtrc010_book.book Page 39 Wednesday, September 1, 1999 10:42 AM
