Specifications

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6720649497 SM HP270-1 2012/09 en
In the ideal cooling circuit the superheat is 0°C. This means that the whole evaporator is being used for
vaporization, and the efficiency is as high as possible
 We need a few degrees of superheat in order to establish the expansion valve operation and make sure
that no liquid is brought inside the suction side of the compressor
Attention: If liquid gets into the compression chamber of a piston compressor it will cause serious damage
High superheat; Frosting on the pipe after the expansion valve, poor efficiency, high hot gas temperature.
Low superheat; Ice and frosting on the suction line to the compressor, evaporating pressure and superheat is
oscillating.
Note: High and Low pressure switch in the refrigeration circuit will activate when pressures are out of range
Adjusting the superheat
In this type of appliances the adjustment of the superheat is made by opening or closing of the expansion valve.
Closing the expansion valve = superheat increase (Less refrigerant is let into the evaporator, causing a lower
evaporating pressure and higher superheat).
Opening the expansion valve = superheat decrease (More refrigerant is let into the evaporator, causing a higher
evaporating pressure and less superheat).
Expansion Valve actuation:
- Suction line to compressor is too cold (too much liquid in evaporator to be boiled properly): decreased
pressure above diaphragm causes valve to close.
- Feeler bulb senses enough heat in suction line – diaphragm makes valve open, allowing more R134a into
evaporator coil.