ICESQUARE / Troubleshooting
What superheat is and why it matters in refrigeration
Superheat is the number of degrees a vapor is above its saturation temperature at the measured pressure. It helps assess evaporator feed and the risk of liquid refrigerant returning to the compressor.
- Vapor reading 8 °C
- Minus saturation −2 °C
- Superheat 10 K
Measure pressure and temperature at the same location
With the system stable, identify the refrigerant and take nearby suction-line pressure and temperature readings. Measure at the evaporator outlet to assess valve feeding, or at the compressor inlet to assess the vapor entering the compressor. Insulate the temperature clamp from ambient air.
Convert pressure to saturation temperature
Use the refrigerant pressure–temperature chart. For blends with glide, use the dew point. Subtract the saturation temperature from the actual tube temperature. If the tube is at 8 °C and the pressure corresponds to −2 °C, superheat is 10 K.
Interpret the reading alongside the load
Low superheat can point to overfeeding or low evaporator load. High superheat can suggest underfeeding, a restriction or operation outside design conditions. Check airflow or water flow, coil condition, subcooling and the valve setting before adjusting.
Guide for trained technicians. Follow the manufacturer’s procedure and limits for the refrigerant and equipment model being serviced.
Technical references
- Danfoss · Dimensioning of Refrigeration Components, Part 2 · “Thermostatic Expansion Valves”
- Danfoss · Ref Tools, Refrigerant Slider · “Dew and Bubble Point”
- Danfoss · Troubleshoot Cold Room Faults · Diagnosis Guide