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RLC-PRC020-EN12
The RLA is based on the motor’s
performance when reaching full rated
horsepower. The kW rating of the motor
will equal or exceed the kW requirement
indicated by the Series R computer
selection program at design conditions.
If motor kW draw at design conditions is
less than the kW rating of the motor, the
RLA at design conditions is determined
by multiplying the motor RLA (at the
desired voltage) by this ratio: design kW/
motor kW rating. This calculation is
performed within the Series R chiller
computer selection program, making
RLA available as part of the design
predictions. Predicted values include
power factor variation from point to
point.
A voltage utilization range is tabulated
for each voltage listed. Series R chillers
are designed to operate satisfactorily
over a utilization range of ±10 percent of
the standard design voltages: (a) 200 V,
230 V, 380 V, 460 V, and 575 V for 60
Hertz, 3-phase, and (b) 380 V, 400 V,
415 V for 50 Hertz, 3-phase.
Evaporator and Condenser Pressure
Drop
Pressure drop data is determined by the
Series R chiller computer selection
program available through local Trane
sales offices.
Part Load Performance
Actual air-conditioning system loads are
frequently less than full-load design
conditions. Depending on the number of
chillers on the job and the load profile,
chillers may operate at full load a small
percentage of the time. With their
excellent part-load performance
characteristics and highly energy-
efficient operation, Series R chillers can
provide significant operating savings at
these part-load conditions.
Selection
Procedure
System Considerations
Part-load chiller operation is frequently
associated with reduced condenser
water temperatures. However, rather
than focusing only on the chiller, it is
important to balance these temperatures
to achieve the most efficient system
operation possible. At part-load
operation, the heat rejected to the
cooling tower is less than at full-load
operation.
Part-load chiller operation is also
typically associated with reduced outside
wet bulb temperatures, resulting in
improved cooling tower performance.
The net result of reduced heat rejection
and lower wet bulb temperatures can be
cooler condenser water entering the
chiller, ultimately improving unit
performance. However, this does not
improve pump or tower efficiency. To
achieve the most efficient system
operation possible, it is best to minimize
the total power draw of the chiller, tower,
and pumps, which may not mean
limiting the condenser water
temperature to what the tower can
provide. To determine specific unit and
system part-load performance for chiller
selection purposes, use the Series R
chiller computer selection program or
contact the local Trane sales office.