RLC-PRC006-EN14
Application
Considerations
Figure A3. Typical series chiller arrangement
Series chiller arrangements can be
controlled in several ways. Figure A3
shows a strategy where each chiller is
trying to achieve the system design set
point. If the cooling load is less than 50
percent of the systems capabilities,
either chiller can fulfill the demand. As
system loads increase, the Chiller 2
becomes preferentially loaded as it
attempts to meet the leaving chilled
water setpoint. Chiller 1 will finish
cooling the leaving water from Chiller 2
down to the system design setpoint.
Staggering the chiller set points is
another control technique that works
well for preferentially loading Chiller 1. If
the cooling load is less than 50 percent
of the system capacity, Chiller 1 would
be able to satisfy the entire call for
cooling. As system loads increase,
Chiller 2 is started to meet any portion of
the load that Chiller 1 can not meet.
Typical Water Piping
All building water piping must be
flushed prior to making the final
connections to the chiller. To reduce heat
loss and prevent condensation,
insulation should be installed. Expansion
tanks are also usually required so that
chilled water volume changes can be
accommodated.
Series Chiller Arrangements
Another energy-saving strategy is to
design the system around chillers
arranged in series. The actual savings
possible with such strategies depends
on the application dynamics and should
be researched by consulting your Trane
Systems Solutions Representative and
applying the Trane System Analyzer
program. It is possible to operate a pair
of chillers more efficiently in a series
chiller arrangement than in a parallel
arrangement. It is also possible to
achieve higher entering-to-leaving chiller
differentials, which may, in turn, provide
the opportunity for lower chilled water
design temperature, lower design flow,
and resulting installation and operational
cost savings. The Trance screw
compressor also has excellent
capabilities for “lift,” which affords an
opportunity for savings on the
evaporator water loop.
