JOHNSON CONTROLS
50
FORM 160.81-NOM1
ISSUE DATE: 10/3/2020
SECTION 3 – OPERATION
The oil leaving the oil eductor manifold block flows
into the compressor to lubricate the compressor bear-
ings. All of the oil that is injected into the compressor
mixes with refrigerant gas during compression. The oil
and refrigerant gas is discharged into the oil separator,
where it is separated and returned to the oil sump. A
high discharge temperature safety is located in the dis-
charge line, between the compressor and oil separator.
This safety will initiate a safety shutdown.
Oil cooling is accomplished by liquid injection into the
discharge of the compressor.
Oil is separated from the refrigerant gas in the oil sepa-
rator in a two step process.
The second and final stage of oil separation is achieved
in the oil coalescing element section of the oil sepa-
rator. The oil mixed with the refrigerant entering the
coalescer element is a very fine aerosol mist about the
size of cigarette smoke particles. These small aerosol
mist particles wet the coalescer element media and
form larger oil droplets which fall by gravity to the
bottom of the coalescer element section. The oil col-
lected in the coalescer section is drained from the oil
separator with a small amount of refrigerant gas. This
provides the high pressure “gas drive” for the eductors
to return oil from the evaporator. Refer to section titled
OIL EDUCTOR CIRCUIT, in next column.
Two sight glasses are provided in the oil separator for
monitoring the oil level and verifying performance of
the coalescer element. Liquid oil should be visible in
the top glass of the oil separator when the chiller is off.
During operation, oil may be higher or lower due to
system load and operating conditions.
An oil drain and charging valve is located on the bot-
tom of the oil separator. A flare connection is provided
for ease of connecting a hose to quickly drain used oil
into a EPA approved recovery cylinder or tank. Oil can
be added into the oil reservoir with the chiller in ser-
vice.
Do not add oil. YORK YR Chiller packages
are pre-charged with the correct amount
of YORK oil during functional testing
after manufacture. Refer to Table 16 on
page 58, YORK Oil Types, in the Section
5 - Maintenance.
Oil loss is most often the result of operating conditions
at loads under 10% of the chillers rated capacity and
with condensing water that is too cold for load and op-
erating condition.
The oil is not “lost” but has migrated into the refrig-
erant charge and is most likely in the evaporator. Ex-
cessive amounts of oil in the evaporator will result in
operational problems.
Oil management problems can result if the compres-
sor discharge superheat drops below 12ºF. Compressor
discharge superheat is the difference between the com-
pressor discharge temperature and the saturated con-
denser temperature. Compressor discharge superheat
is used in conjunction with the evaporator approach to
determine the most efficient refrigerant charge.
Should the control panel display EXCESS
CHARGE WARNING this is most likely
the result of excessive amounts of oil in
the evaporator. Excess amounts of oil in
the refrigerant will cause foaming. The
oil foam carries liquid refrigerant into
the compressor. This results in lowering
the compressor discharge superheat to
low levels. If the compressor discharge
superheat falls to within 10°F (69°C) of
the saturated condensing temperature
the control panel will display EXCESS
CHARGE WARNING. Compressor load-
ing will be inhibited while the EXCESS
CHARGE WARNING is displayed. The
inhibit loading will remain in effect until
the compressor discharge superheat in-
creases to 15°F (69°C).
OIL EDUCTOR CIRCUIT
An oil eductor circuit is provided to properly manage
the amount of oil in the refrigerant charge. A small
amount of oil is normal in the refrigerant charge and
will be found in the evaporator. If not properly man-
aged the oil will accumulate and have adverse conse-
quences regarding chiller performance.
The oil eductor circuit consists of oil filter drier, educ-
tors, and interconnecting piping. Refer to
The eductors operate using the “jet pump” principle.
Discharge pressure gas and oil flows through a filter
dryer located at the oil separator. YR Chillers are sup-
plied with a variable orifice arrangement. The reduced
pressure (pumping action) is created by the velocity of
the discharge pressure gas and oil flowing through the
orifice and nozzle. This creates a reduced pressure area
that allows the oil-rich refrigerant and oil to flow from
the evaporator into the compressor.
