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3.0 Refrigerant Control
3.1 Suction and Interstage Piping
To avoid problems related to refrigerant and/or oil control,
piping design is crucial. Carlyle requires suction and mid-
stage header designs that do not allow free draining of
refrigerant or oil into an off compressor. This avoids liquid
refrigerant and oil accumulation in off compressors or
suction line traps (see Fig. 10 for piping recommenda-
tions.) For that reason, suction and mid-stage manifolds
are recommended to be located below their respective
compressor inlet locations. However, this lower location
does not eliminate the need to avoid refrigerant and
especially oil from accumulating in large quantities in
these manifolds. Unless this is avoided, large slugs of liq-
uid refrigerant and especially oil can be drawn into run-
ning compressors. To avoid this, piping must be
configured as shown in the figure below. If suction or
interstage piping is to be located above the compressor
the recommendations in the figure below also apply.
Suction and Midstage Header Above Compressors
Suction and Midstage Header Below Compressors
Fig. 10 — Piping Recommendations
22
Interstage manifolds are commonly applied with parallel
06CC rack designs and are frequently used to provide a
point of connection for the suction side of the subcooler
or economizer. The cool suction gas exiting the subcooler
is used to provide additional motor cooling in 06CC mod-
els. This design reduces the amount of liquid injection
required for motor cooling. These manifolds act to effi-
ciently distribute cool refrigerant gas to the interstage
connection points of all applied 06CC model compres-
sors. To prevent uneven distribution of the cool refrigerant
gas, the suction line of the subcooler must be connected
to the interstage manifold near the center of the manifold.
This design allows for reduced liquid injection at the
peripheral compressor models due to more even refriger-
ant gas flow. End feeding the interstage manifold results
in poor liquid distribution to the compressors if flooding
occurs. The individual line to each compressor from the
common interstage manifold should be piped from the
top of the manifold for best liquid distribution if flooding
occurs.
To help prevent liquid refrigerant floodback and oil slug-
ging into the suction inlet of the Carlyle
Cooling compressors, a suction accumulator should be
used in conjunction with a properly designed suction
manifold, although use of a well designed and sufficiently
oversized suction manifold may also suffice. In multiple
compressor applications, one large accumulator mani-
folded to individual compressors is recommended rather
than smaller individual accumulators on each compres-
sor.
®
Compound
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