Specifications

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FORM 160.80-NOM1
YORK INTERNATIONAL
SECTION 3 – OPERATION
BASIC DESCRIPTION
The YORK YS Chiller package uses a refrigerant-
flooded evaporator and a liquid-cooled condenser. The
compressor is a heavy-duty, industrial-rated rotary screw
compressor. The YS package consists of four major com-
ponents - Driveline, Oil Separator, Condenser, and
Evaporator. Refer to the Chiller Package Component
drawing, Figure 14.
COMPONENTS
Driveline
The driveline is made up of the compressor and a
2-pole industrial induction motor. The motor is mounted
to the compressor with a “D”-flange spacer. The “D”-
flange eliminates the necessity to align the motor and
compressor.
The compressor is a positive displacement, variable vol-
ume, direct drive, twin helical rotary screw compressor.
The male rotor is a direct drive by the motor; the female
rotor is an idler that is driven by the male rotor. The
rotors do not touch each other or the compressor hous-
ing. The rotors are separated by a hydraulic oil seal,
which prevents high pressure gas from leaking into low
pressure areas.
Evaporator pressure gas is drawn into the compressor
and compressed by the male and female rotors as they
rotate together and reduce the volume of gas.
The compressor bearings are industrial duty rated, anti-
friction rolling element bearings. No sleeve bearings are
used. Oil is injected into the compressor by differential
pressure to lubricate the bearings, seal the rotors and re-
move the heat of compression. The oil that is injected into
the compressor mixes with the compressed gas and is
separated from the refrigerant gas in the oil separator.
A slide valve is positioned between the male and female
rotors, that moves axially to match the compressor ca-
pacity to that of the evaporator refrigeration load. The
slide valve is moved by differential pressure. As the slide
valve moves toward the unloaded position, less suction
gas is pumped through the compressor. The control panel
automatically positions the slide valve to match the load
requirements. The slide valve can be operated manually.
When the compressor is shut off, a spring returns the
slide valve to unloaded position. The compressor starts
with the slide valve in the unloaded position.
Oil Separator
The oil separator removes the oil that was injected into
the compressor. The oil separator is a three stage de-
sign. Most of the oil separates by a reduction in velocity
in the first stage. The discharge gas is then directed
through a high surface area that collects more of the
oil. The final stage is a coalescer element(s) that re-
moves the fine aerosol particles of oil.
The oil separator is very efficient and removes nearly
100% of the oil. The very small amount of oil that does
pass through the oil separator is returned to the com-
pressor through a filter drier.
The oil separator is also a reservoir for the oil. A tem-
perature controlled immersion heater is installed in the
oil reservoir. The oil heater is interlocked with a low oil
level safety switch.
Condenser
Oil free refrigerant gas leaving the oil separator flows
into the condenser. Water flowing through the condenser
tubes removes the evaporator heat load, the heat of com-
pression and condenses the refrigerant gas into refrig-
erant liquid.
The liquid refrigerant then flows through the integral
liquid sub-cooler located in the bottom of the condenser.
The sub-cooled liquid refrigerant flows into the evapo-
rator by deferential pressure.
Evaporator
Condensing pressure refrigerant flows out of the liq-
uid sub-cooler into the liquid line where the liquid re-
frigerant is metered into the evaporator by an orifice.
The liquid refrigerant begins to flash (and cool) after
flowing through the orifice plate. The refrigerant is
distributed in the bottom of the evaporator. Liquid re-
frigerant floods the evaporator and the heat is ex-
changed from the chilled liquid, flowing on the inside
of the evaporator tubes, to the liquid refrigerant on the
outside of the tubes.
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