Refrigeration System Operation - Scotsman FDE470 Service Manual

Refrigeration System Operation

The FDE470 uses a forced draft condenser,
capillary tube and hermetic compressor. The
system uses R-134a as a refrigerant. High
pressure, high temperature refrigerant is forced
thru the condenser where it looses enough heat to
condense. The high pressure liquid refrigerant
then passes thru the capillary tube which causes a
pressure drop in the evaporator. As the high
pressure liquid refrigerant moves into the
evaporator's area of low pressure, the warm water
and low pressure cause the refrigerant to
evaporate and absorb heat from the metal walls of
the evaporator. After the refrigerant has flowed thru
the evaporator it goes back to the compressor thru
the suction line as a low pressure vapor. At the
compressor the cycle is repeated.
The FDE470 uses a low side pressure control as a
safety, it will shut the system down if the suction
pressure is too low for reliable operation.
Evaporator
Compressor
Re f r i g e r a t i on Sy s t e m Sc he m a t i c
System Characteristics:
Typical Low Side Pressure:
13 - 14 PSIG
Typical Discharge Side Pressure:
135 - 175 PSIG
System Refrigerant Charge:
14 ounces of R-134a
Capillary Tube
August 1994
Page 11
FDE470
Dryer
Air Cooled
Condenser