Operation: Refrigeration - Scotsman FME1504R Service Manual

OPERATION: Refrigeration

Beginning at the compressor, the refrigerant is
compressed into a high temperature gas. The
discharge line directs this gas to the condenser
and to the head pressure control At the remote
condenser the gas is cooled by air and it then
condenses into a liquid. This high pressure liquid
then goes through the liquid line to the liquid line
connection at the head pressure control. If the
head pressure is high enough the liquid refrigerant
will go through the valve and enter the receiver.
From the receiver, the liquid refrigerant flows
through the liquid line valve and then to the
expansion valve.
The thermostatic expansion valve meters liquid
refrigerant into the evaporator, the volume of
liquid refrigerant depending upon the temperature
DISCHARGE
LINE
HEAD
PRESSURE
CONTROL
VALVE
RECEIVER
of the evaporator; warmer evaporators get more
refrigerant and colder evaporators get less. At the
evaporator, the refrigerant enters an area of
relatively low pressure, where it can easily "boil off"
or evaporate. As it evaporates, it absorbs heat
from the evaporator and whatever is in contact with
it (such as the water inside it). After the
evaporator, the refrigerant, now a low pressure
vapor, goes through the suction line back to
compressor, where the cycle is repeated.
LIQUID LINE
LIQUID LINE
January 2000
Page 17
NME1254R & FME1504R
REMOTE CONDENSER
DETAIL OF HEAD
PRESSURE CONTROL
VALVE
VALVE
THERMOSTATIC
EXPANSION
COMPRESSOR
VALVE
EVAPORATOR