Specifications

44 YORK INTERNATIONAL
oil separator and the condenser, allows all of the refrig-
erant charge to be stored in the condenser.
A ½ inch liquid refrigerant supply is piped from the bot-
tom of the liquid line to the refrigerant cooled oil cooler.
The refrigerant gas from the oil cooler is piped directly
into the evaporator.
A liquid refrigerant-charging valve is piped into the liq-
uid line between the evaporator and the metering ori-
fice. A ¾ inch male flare connection is provided for
connecting hoses or transfer lines.
CAPACITY CONTROL
Refer to the Capacity Control Piping Schematic piping,
Fig. 26.
Capacity control is accomplished by using differential
pressure to move the slide valve. As the slide valve is
moved axially between the compressor rotors the vol-
ume of gas pumped by the compressor is changed to
match the system requirements.
Leaving evaporator fluid temperature is continuously
monitored by the microprocessor. The Leaving Evapo-
rator fluid temperature is compared to the Leaving
Evaporator fluid Set Point. When the leaving evapora-
tor fluid temperature is beyond the range of the set point
value a signal is sent to the relay output board. A signal
is sent from the relay output board to energize the
4-way valve directional solenoid valves.
When Solenoid Valve B is energized the slide valve be-
gins to move in the load direction. The 4-way direc-
tional valve opens Port P to Port B and Port A to Port
T. Oil pressure from the oil circuit flows into the 4-way
solenoid valve sub-plate manifold at Port P. Oil pres-
sure flows through the sub-plate manifold block and out
Port B to Compressor Port SC-2. Simultaneously, oil
flows out of Compressor Port SC-1 into Port A on the
sub-plate manifold, through the sub-plate manifold block
and out of the sub-plate manifold block at Port T to
suction pressure.
When the Solenoid Valve A is energized, the slide valve
will move in the unload direction. The 4-way directional
valve opens Port P to Port A and Port B to Port T. See
Figure 24. High pressure oil flows into Compressor Port
SC-1 and oil is relieved out of Compressor Port SC-2 to
suction pressure.
A slide valve potentiometer is used to provide feedback
to the microprocessor to display slide valve position as
a percentage of full load. See Fig. 25.
Four manual isolation valves are incorporated into the
4-way solenoid sub-plate to isolate the 4-way directional
valve for service. Remove the steel hexagonal caps to
gain access to the service valve stem. Use a refrigera-
tion service valve wrench to close or open the valves.
FIG. 24 – 4-WAY DIRECTIONAL VALVE SUBPLATE
SERVICE ISOLATION
VALVE CAP
PORT “T”
PORT “A”
PORT “P”
PORT “B”
00093VIP
FIG. 25 – SLIDE VALVE POTENTIOMETER
LD05117
PHOTO TO COME
Operation