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 9 of 61
1.5 External Adjustment of Vi
a) Determine P
d
/P
s
during operation based on the anticipated operating conditions of the system.
P
d
/P
s
= Absolute value of discharge pressure = Discharge gauge pressure + 1.033 kgf/cm
2
Absolute value of suction pressure Suction gauge pressure + 1.033 kgf/cm
2
b) Find V
i
from the compression ratio
Vi = (P
d
/P
s
)
1/k
or Vi
k
= P
d
/P
s
Vi can be found directly from the graph. (Working pressure is, however, absolute pressure)(Fig. 12)
c) After determining the port, set the capacity control mechanism to the unload position.
d) Determine the number of turns needed on the Vi changing rod for the particular compressor as
given in Fig. 13.
e) Remove the cap seal on the Vi changing rod and loosen the lock nut.
Turn the Vi changing rod clockwise (CW) and confirm that the variable Vi slide valve is at the
maximum Vi position and that the Vi changing rod does not rotate (unreasonable force should
be avoided when turning the Vi changing rod). (Adjusted to H port configuration before
shipment). In case of medium port (M port), turn the Vi changing rod clockwise (CW) until it
stops and set the variable Vi slide valve to the H port position.
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