JOHNSON CONTROLS
45
FORM 160.81-NOM1
ISSUE DATE: 10/3/2020
3
SECTION 3 – OPERATION
BASIC DESCRIPTION
The YORK YR Chiller package uses a refrigerant-
flooded evaporator and a liquid-cooled condenser. The
compressor is a heavy-duty, industrial-rated rotary
screw compressor. The YR package consists of five
major components – Driveline, Oil Separator, Con-
denser, Evaporator and OptiView™ Control Center.
COMPONENTS
Driveline
The driveline is made up of the compressor and a
2-pole industrial induction hermetic motor. The motor
is mounted to the compressor which eliminates the ne-
cessity to align the motor and compressor.
The compressor is a positive displacement, variable
volume, direct drive, twin helical rotary screw com-
pressor. The male rotor is a direct drive by the motor;
the female rotor is an idler that is driven by the male ro-
tor. The rotors do not touch each other or the compres-
sor housing. 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 differ-
ential pressure to lubricate the bearings, seal the rotors
and remove the heat of compression. The oil that is in-
jected 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 fe-
male rotors, that moves axially to match the compres-
sor capacity 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 two stage design.
Most of the oil separates by a centrifugal force in the
first stage. The final stage is a coalescer element(s) that
removes 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 an evaporator eductor.
The oil separator is also a reservoir for the oil. A tem-
perature controlled immersion heater is installed in the
oil reservoir.
Condenser
Oil free refrigerant gas leaving the oil separator flows
into the condenser. Water flowing through the con-
denser tubes removes the evaporator heat load, the heat
of compression and condenses the refrigerant gas into
refrigerant liquid.
The liquid refrigerant then flows through the integral
liquid sub-evaporator located in the bottom of the con-
denser. The sub-cooled liquid refrigerant flows into the
evaporator by deferential pressure.
Evaporator
Condensing pressure refrigerant flows out of the liquid
sub-evaporator into the liquid line where the liquid re-
frigerant is metered into the evaporator by a variable
orifice. The liquid refrigerant begins to flash (and cool)
after flowing through the orifice. The refrigerant is dis-
tributed in the bottom of the evaporator. Liquid refrig-
erant floods the evaporator and the heat is exchanged
from the chilled liquid, flowing on the inside of the
evaporator tubes, to the liquid refrigerant on the out-
side of the tubes.