REFRIGERATION DIVISION
V SERIES
SCREW COMPRESSOR HANDLING MANUAL
Supersedes all previous version. This information is for reference use only and subject to change without notice
Revision 2 (June 05,2000) Page 8 of 61
As shown in Fig. 10A, the radial port of a conventional model becomes larger as Vi becomes smaller.
In the case of V-Series compressors, the stop position of the variable Vi unloader slide valve moves to
the discharge side and changes Vi by reducing the size of the radial port at full load operation.
As Fig. 11 shows, the refrigeration capacity changes only slightly under various Vi and other
conditions. Refrigeration capacity is influenced considerably by shaft power but changes little in
response to slight changes in operating conditions, as the diagram shows, consequently, once Vi is
adjusted to the operating conditions, it is not necessary to alter it in response to slight changes in
operating conditions.
Fig. 10-A Difference between Conventional Fig. 11 Conventional Screw Capacity Curve
Discharge Port and V-Series Discharge Port
The Vi must be adjusted only when there are major changes in operating conditions such as a change
in the application of the compressor. For instance, when the operating conditions of the compressor
are changed from cooling at approx. 0qC evaporative temperature to refrigeration at -40q C
evaporative temperatures with the compressor Vi set to the L port configuration, shaft power must be
double. In such a case it is advisable to change the Vi to the H port configuration. Similarly, if the
compressor is to be used for refrigeration at an evaporative temperature of 0qCa-30qC, it is advisable
to set the Vi to the M port configuration.
Temperature drops and the compression ratio “Vi” increases as refrigeration progresses but Vi should
not be changed according to the varying conditions. The Vi should be fixed during operation (when Vi
must be changed according to operating conditions, a Maximizer Screw Compressor, namely a new
V-Series unit, should be used).
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