Measure the temperature of the liquid line. Take the temperature as close as possible to the expansion valve, before the metering device, for accurate results. The metering device controls the flow of liquid refrigerant in a system and is located between the condenser and the expansion valve on the liquid line. Attach a digital thermometer to the liquid line to take the temperature. Use twist ties to hold it in place.
Calculate the liquid line pressure of the cooling device. Attach a pressure gauge to the liquid services valves. The gauge will display the pressure in pounds per inch.
Convert the liquid line pressure to a boiling point temperature by using the refrigerant product's chart or gauge. Check that you have the proper gauge or chart for the type of refrigerant used.
Subtract the liquid line temperature from the boiling point, also referred to as saturation temperature at pressure, to check the subcooling amount. This will tell you the correct amount of subcooling that has been performed by the device.
Things You Will Need
- Digital thermometer
- Twist ties
- Pressure gauge
- Temperature chart or gauge
- Another way to check or calculate subcooling is to use a subcooling instrument, based on the type of refrigerant used. Hook the pressure port on the instrument to the liquid line. Attach the thermocouple to the liquid line. The device will produce a digital readout of the amount of subcooling performed.
- Leave the pressure gauge attached for up to 10 minutes, so it accurately reads the temperature.