Product specifications

19
Oversizing Chillers
Ove rsi zi n g of chillers more than 5-10% is not
recommended. Oversizing causes energy inefficiency
and shortened compressor life due to excessive
compressor cycling. Larger future load requirements
may cause temporary oversizing of equipment which
will require careful unit selection. It may be better to
properly size for the present load and add another unit
later for future expansion. It is also recommended using
multiple units where operation at minimum load is
critical. Fully loaded equipment operates better and
more efficiently than large equipment running at or
near minimum capacity.
Hot gas bypass should not be a means to allow
oversizing of chillers. Hot gas bypass should only be
used where the equipment is sized properly for full
load but the load turn down is less than the minimum
unloading step available. See Table 1 on Page 8 for
estimated hot gas bypass turndown.
Sound and Vibration
ACDS-B compressors are mounted with rubber
grommets to the frame to absorb sound and vibration.
The compressors are not mounted on springs because
extra movement may cause line breakage and
refrigerant leaks. Unit isolation helps prevent any
remaining sound or vibration from entering the building
structure, piping or electrical service.
Water (Fluid) Strainers
It is recommended that 40-mesh strainers be installed
in the fluid piping as close to unit cooler as possible.
Multiple Chillers Per Chilled Water System
1. Where the load is greater than one ACDS-B can
supply or where standby capacity is required or
the load profile dictates, multiple chillers may be
piped in parallel. Units of equal size help to ensure
fluid flow balance, but balancing valves ensure
balanced flows even with dissimilar sized chillers.
Tem p e r a t u re c o n trol l e r s e n s o r s m a y o r ma y n o t
need to be moved to the common fluid piping
depending on the specific application.
2. Parallel Chiller Applications (Figure 12a). Both units
operate simultaneously modulating with load
variations. Each unit operates independently
sensing its own leaving water temperature. The
set point of each thermostat is set to maintain the
desired loading scheme.
Figure 12a
3. Series Chiller Applications (Figure 12b)
Where a large temperature range is required (over
25°F [13.9°C]), the chiller may be piped in series.
In this case the units are controlled independently.
The load is progressive by temperature so the chiller
selections are critical.
Figure 12b
R-OUT R-IN
W-IN
W-OUT
R-OUT R-IN
CHILLER
CHILLER
No. 2
No. 1
T
T
T
R-OUT R-IN
FLUID-IN FLUID-OUT
R-OUT R-IN
CHILLER
CHILLER
T
APPLICATION DATA (CONT.)