The Subcooling Process
At saturation temperature, refrigerants can be a mix of both liquid and vapor. To ensure the proper operation of the metering device and indoor coil it is essential that enough heat is removed from the refrigerant so that it is 100% liquid. To do this the system is designed with additional coil circuitry to reject additional heat so that the refrigerant is well below the saturation temperature. If the saturation temperature is 126F, a properly charged system will cool the liquid approximately 16 more degrees below the saturation temperature. This subcooling occurs in the condensing coil after all of the hot gas has been condensed into a liquid. The process of removing heat from the refrigerant so that its’ temperature is below the saturation temperature is called Subcooling.Steps to Measuring Subcooling
- Attach your high side (liquid side) refrigerant gauge on the liquid line service port at the condenser coil. You can identify the liquid line because it is the smaller of the two refrigerant lines.
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Place a clamp on digital temperature probe near the outlet of the condenser coil. Somewhere near the service port.
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Read and record the pressure and corresponding temperature from your high side gauge. In this example, 450 PSIG for R-410A and 281.7 PSIG for R-22, both of these temperatures correspond to 126F.
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Read and record the temperature from you digital temperature probe. In this example, 110F.
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Subtracting the digital temperature from the temperature record from your gauges shows that the refrigerant leaving the coil is 16F cooler than the saturation temperature.
by Ron Walker