All installations and services must be performed by qualified service personnel.
3.Condenser Subcooling:
Before taking subcooling measurements, allow the system to stabilize through continuous operation for at least 15 minutes. To determine subcooling, measure the refrigerant pressure at the liquid line as it leaves the condenser. It is preferable to measure pressure of the liquid line at the evaporator, but most manufacturers, including Thermo Pride, do not include test ports (or Schraeder valves) at the evaporator. Typically, it would be necessary to compensate for the pressure drop through the line connecting the condenser and the expansion valve. However, due to the close proximity of these components, the pressure drop will be small and can be neglected.
Once the liquid line pressure is known, the refrigerant temperature must be taken on the liquid line as it enters the evaporator. Use a good resistive thermometer or thermocouple protected with a rag or insulation. Subtract the measured temperature from the saturation temperature of the refrigerant. The result is the degree of refrigerant subcooling.
Refer to Example 4, in Appendix B: Calculations of this manual, for a sample calculation of how to figure the degree of subcooling for the condenser. In general, Thermo Pride recommends the evaporator operate with a subcooling of between 10°F and 15°F.
4.Definition of Superheat:
Superheat is extra heat added to refrigerant above the vaporization pressure/temperature of the refrigerant. A small amount of refrigerant superheat is usually beneficial and needed to help assure the best operation of the cooling system.
Superheat cannot be measured with a pressure gauge alone. Both pressure and temperature readings of the suction line are required to evaluate the amount of refrigerant superheating. The degree of superheating gives an indication of two important
Highly superheated vapor is also detrimental to system operation. The highly superheated refrigerant may overheat the compressor, resulting in premature failure and/or intermittent thermal cutout of the compressor. High superheat at the evaporator also indicates the evaporator is operating very inefficiently by vaporizing the refrigerant too quickly in the evaporator coil. High superheat at the evaporator results in some loss of the evaporator heat removal capacity.
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