Oil Eductor Circuit - York MILLENNIUM YS Manual

OIL SYSTEM (CONT'D)
lets are collected on the extended surface area of the
wire mesh pads where the oil falls by gravity into the oil
reservoir.
The third and final stage of oil separation is achieved in
the oil coalescing element section of the oil separator.
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 par-
ticles wet the coalescer element media and form larger
oil droplets which fall by gravity to the bottom of the
coalescer element section. The oil collected 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 paragraph Oil Eductor
Circuit.
Three 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 sys-
tem load and operating conditions.
A low oil level safety switch is provided in the bottom of
the oil separator. A safety shutdown will be initiated if
the oil level is below the switch setting for 30 continu-
ous seconds after the chiller has been running for 3 min-
utes.
An oil drain and charging valve is located on the bottom
of the oil separator. A 5/8 inch male 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
service.
Do not add oil. York YS Chiller pack-
ages are pre-charged with the correct
amount of York oil during functional
testing after manufacture. Refer to the
Oil Usage Table 6 in the Maintenance
Section.
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.
YORK INTERNATIONAL
The oil is not "lost" but has migrated into the refrigerant
charge and is most likely in the evaporator. Excessive
amounts of oil in the evaporator will result in opera-
tional problems.
Oil management problems result if the compressor dis-
charge superheat is not maintained at the values listed
in Table 8. Compressor discharge superheat is the dif-
ference between the compressor discharge tempera-
ture and the saturated condenser temperature. Com-
pressor discharge superheat is used in conjunction with
the evaporator approach to determine the most efficient
refrigerant charge.
Should the control panel display EX-
CESS CHARGE WARNING this is
most likely the result of excessive
amounts of oil in the evaporator. Ex-
cess amounts of oil in the refrigerant
will cause foaming. The oil foam car-
ries liquid refrigerant into the com-
pressor. This results in lowering the
compressor discharge superheat to
low levels. If the compressor discharge
superheat falls to within 10ºF of the
saturated condensing temperature the
control panel will display EXCESS
CHARGE WARNING. Compressor
loading will be inhibited while the
EXCESS CHARGE WARNING is
displayed. The inhibit loading will re-
main in effect until the compressor
discharge superheat increases to 15ºF.

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 three refrigerant and
oil filter driers, two "jet pump" eductors and the inter-
connecting piping. Refer to Figures 20 and 21.
The eductors operate using the "jet pump" principle.
Discharge pressure gas and oil flows through a filter
dryer located at the bottom of the oil separator. The
FORM 160.47-NOM3
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