York YCAJ44HE8, Installation, Operation And Maintenance Manual, Page: 68 / 92

68 YORK INTERNATIONAL
“Z” COMPRESSOR (STYLE B)
LOADING /UNLOADING
An external line, connected to the discharge side of the
compressor, supplies high pressure gas to the unloader
mechanism which is mounted next to the associated
bank of cylinders. The unloader mechanism consists of
a solenoid valve integrally mounted on the outside of the
cover plate, and an internal spring loaded piston.
“J” COMPRESSOR (STYLE G)
LOADING/UNLOADING
An internal line, connected to the discharge side of the
compressor, supplies high pressure gas to the unloader
mechanism which is mounted next to the associated
bank of cylinders. The unloader mechanism consists of
a solenoid valve integrally mounted on the outside of the
cover plate, and an internal spring loaded piston.
NOTE: 6 cylinder compressors do not connect the loading sole-
noid wiring on cylinders 1 & 2, effectively making them
permanently loaded in the “standard” unloading scheme.
The loading solenoid wiring on these cylinders are con-
nected to additional electronics for extra steps of unload-
ing. Currently, extra steps of unloading are not available.
Cylinders 3 & 4 have no loading solenoids and are “truly”
permanently loaded.
FIG. 27 – “Z” COMPRESSOR UNLOADING
SEQUENCE
UNLOADING
When the solenoid valve is energized, discharge gas
pressure is applied to the top of the unloader piston, forc-
ing it down against spring pressure. The bottom end of
the piston seats against the recessed opening to the
suction plenum, effectively blocking the flow of suction
gas into the cylinders (blocked suction unloading). The
cylinders are now unloaded.
LOADING
When the solenoid valve is de-energized, gas pressure
on top of the unloader piston is relieved to the suction
plenum. The coil spring forces the piston up, uncovering
the recessed opening which allows the suction gas to
flow through the port and into the cylinders. The cylin-
ders are now loaded.
UNLOADING
When the solenoid valve is energized, discharge gas
pressure is applied to the top of the unloader piston, forc-
ing it down against spring pressure. The bottom end of
the piston seats against the recessed opening to the
suction plenum, effectively blocking the flow of suction
gas into the cylinders (blocked suction unloading). The
cylinders are now unloaded.
LOADING
When the solenoid valve is de-energized, gas pressure
on top of the unloader piston is relieved to the suction
plenum. The coil spring forces the piston up, uncovering
the recessed opening which allows the suction gas to
flow through the port and into the cylinders. The cylin-
ders are now loaded.
NOTE: 6 cylinder compressors do not connect the loading sole-
noid wiring on cylinders 1 & 2, effectively making them
permanently loaded in the “standard” unloading scheme.
The loading solenoids on these cylinders are connected
to additional electronics for extra steps of unloading.
Currently, extra steps of unloading are not available. Cyl-
inders 3 & 4 have no loading solenoids and are “truly”
permanently loaded.
FIG. 28 – “J” COMPRESSOR UNLOADING
SEQUENCE
LD02181
LD02182