Scotsman FME804R Service Manual page 19

OPERATION: Refrigeration
The refrigeration system under low condenser air
temperatures is much the same as it is under
higher temperatures, with the exception that the
resulting low head pressures cause the head
pressure control to close off the liquid line between
the condenser and the receiver.
DISCHARGE
LINE
HEAD
PRESSURE
CONTROL
VALVE
Low Condensing Temperature
LIQUID LINE
KING
VALVE
RECEIVER
January 2000
NME654R & FME804R
This forces more refrigerant into the condenser
(with a small amount of discharge gas going into
the receiver to maintain pressure until the head
pressure is built back up to the rated gauge
pressure of 180 PSIG). At that pressure the valve
opens up the liquid line from the condenser to the
receiver.
Refrigeration Schematic
DETAIL OF HEAD
PRESSURE CONTROL
VALVE
LIQUID LINE
VALVE
SUCTION
LINE
COMPRESSOR
Page 19
REMOTE CONDENSER
THERMOSTATIC
EXPANSION
VALVE
EVAPORATOR