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INSTALLATION AND SERVICE MANUAL 917N-CMT, 927CMT, 957CMT
184617-02
10.1 The Refrigeration System
(See Figures 10-1 and 10-2) The com-
pressor discharges the refrigerant to the
condenser as a high-temperature, high-
pressure gas. Either by water-cooling or
air-cooling, the refrigerant gas con-
denses to liquid. This high pressure
liquid flows into the receiver which serves
as the refrigerant reservoir. Upon leaving
the receiver, the refrigerant flows through
the filter drier, sight glass, and cylinder
solenoid valve (which is controlled by the
cylinder thermostat).
When the cylinder thermostat calls for
cooling, the cylinder solenoid coil is
energized and the valve opens to permit
the flow of refrigerant to the automatic
expansion valve. This expansion valve
controls the flow of refrigerant in the
evaporator in such a way as to keep
practically the entire coil filled with
evaporating refrigerant.
As the refrigerant in the cylinder evapo-
rator absorbs the heat, it changes to a
low pressure vapor. This vapor is re-
turned to the low pressure side of the
compressor through the suction line
leading from the freezing cylinder, thus
completing the refrigeration cycle.
In water-cooled systems the flow of
cooling water to the condenser is me-
tered by a pressure-controlled regulating
valve. Here, two forces control the size of
the valve opening through which con-
denser water may flow. An adjustable
tension spring tends to keep the valve
closed while a bellows, connected by
tubing to the high-pressure side of the
system, tends to open the valve. When
the refrigeration system begins opera-
tion, the increased pressure caused by
the compressor opens the water regulat-
ing valve and permits water to flow
through the condenser. When the unit
cycles off, the water continues to flow
through the valve until the condensing
pressure has decreased below the valve
setting. (See Section 8.2, for settings.)
10 Equipment Operation