JOHNSON CONTROLS
49
SECTION 3 – OPERATION
FORM 160.81-NOM1
ISSUE DATE: 10/3/2020
3
Variable Orifice
Since liquid refrigerant is transferred from the Con-
denser to the Evaporator via the Condenser-Evaporator
pressure differential, a large differential can create an
excess refrigerant level in the evaporator. A small dif-
ferential can result in insufficient level in the Evapora-
tor. To maintain an appropriate refrigerant level in the
Evaporator under all conditions, the chiller is equipped
with a variable orifice. To maintain an appropriate re-
frigerant level in the Evaporator under all conditions,
a Variable Orifice is located in the refrigerant line be-
tween the condenser and evaporator. A liquid level
sensor, located in the condenser, detects the refriger-
ant level. The refrigerant level in the condenser is ex-
pressed as 0% (minimum) to 100% (maximum). While
the chiller is shut down, an open signal is applied to
the actuator, driving the orifice to the fully open po-
sition. When the chiller is started, a close signal is
applied to the Orifice actuator for the duration of the
“Start Sequence Initiated” period. This positions it to
approximately the 75% closed position prior to starting
the compressor motor, which occurs at the end of the
“Start Sequence Initiated” period. To allow for actua-
tor timing variances and assure the valve is positioned
at the 75% closed position, the duration of the “Start
Sequence Initiated” period is programmable.
OIL SYSTEM
Refer to the Oil Piping Schematic Drawing,
and the Filter Driers and Oil Eductor,
.
Oil flows from the oil separator into the compressor by
differential pressure. The oil flows from the oil separa-
tor through a 3 micron oil filter (or optional dual oil
filters). Filtered oil then flows to a oil manifold that is
located at compressor.
The oil pressure transducer is located on the compres-
sor. The differential pressure is measured as the dif-
ference between the Oil Pressure Transducer and the
Discharge Pressure Transducer, located on discharge
housing of compressor. This value is compared to the
limits in the control panel logic. If the oil filter differ-
ential reaches 20 PSID, a warning message is displayed
by the control panel display. If the oil filter reaches 25
PSID, a safety shutdown is initiated.
OIL
CHARGING
VALVE
OIL FILTER
OIL SOLENOID VALVE
FILTER DRYER
FILTER
DRYER
EDUCTOR
FIGURE 20 -
OIL FILTER SYSTEM
LD07964
