Liquid Refrigerant Circuit; Dual Service Chillers; Filter Driers And Oil Eductor; Variable Orifice Pressure Differential Setpoints - York MILLENNIUM YS Manual

Operation
OIL EDUCTOR CIRCUIT (CONT'D)
discharge pressure gas and oil flows through a regulat-
ing orifice and nozzle located in the eductor block. 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.
Oil-rich refrigerant flows into the eductor block through
the filter drier from the evaporator. The oil rich refrig-
erant mixes with the discharge pressure gas and flows
into the compressor suction line.
A second eductor flows oil, which may have collected
in the evaporator trough through the second filter drier
located on the eductor block. This oil mixes with the
discharge gas in the eductor block and flows to the com-
pressor at port SC-5.
The filter driers should be changed annually or when
excessive amount of oil is indicated in the refrigerant
charge.
HIGH PRESSURE OIL AND REFRIGERANT
FROM OIL SEPARATOR
FILTER DRIERS
PRESSURE RELEASE
VALVE
FIG. 20 – FILTER DRIERS AND OIL EDUCTOR

LIQUID REFRIGERANT CIRCUIT

Liquid refrigerant flows from the condenser into the
evaporator by differential pressure. Sub-cooled liquid
refrigerant flows out of the condenser into the liquid
line. A metering orifice is installed in the liquid line to
control the rate liquid refrigerant flows into the evapo-
rator. The orifice is selected based upon the operating
conditions of the chiller. Refer to Figure 22.
34
YS Chillers (S0 – S5) are supplied with a variable ori-
fice arrangement. In parallel with the metering orifice
is a solenoid valve and hand-throttling valve. The sole-
noid is energized open by the DIFFERENTIAL PRES-
SURE set point that is field programmable from the
panel. The differential pressure between condensing
pressure and evaporating pressure is compared to the
set point value. When the differential pressure is at or
less than the setpoint, the solenoid valve is energized
open. The solenoid valve is de-energized closed when
the differential pressure is equal to or greater than the
setpoint plus 10 psig. A hand-throttling valve is provided
to adjust the refrigerant flow rate through the solenoid
valve to match the system operating conditions.
Dual Service Chillers – Ice duty and comfort cooling
air conditioning applications will require the solenoid
valve to be energized open in the air conditioning mode
of operation since this represents the low differential
pressure mode of operation.
The differential pressure set point is field programmable
within the ranges specified in Table 5 for different re-
frigerants and EPROM version S.01F.17 and later. See
York Service Bulletin 160.47-M2 (SB18) for program-
ming instructions.
TABLE 5 – VARIABLE ORIFICE PRESSURE
A liquid line hand-isolation valve is located between the
condenser and the metering orifice plate. This valve, in
EDUCTOR
combination with the hand isolation valve between the
MANIFOLD BLOCK
oil separator and the condenser, allows all of the refrig-
00089VIP
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.
DIFFERENTIAL SETPOINTS
REFRIGERANT
PRESSURE RANGE
R-22
R-134A
DIFFERENTIAL
25 - 150 PSID
15 - 110 PSID
YORK INTERNATIONAL