A system with a restricted metering device typically shows:

Superheat = actual suction line temperature − saturation temperature (from suction pressure for that refrigerant). It indicates how completely the refrigerant boiled off in the evaporator and helps protect the compressor from liquid floodback. Why it matters: • Too LOW superheat → risk of liquid entering compressor (floodback) • Too HIGH superheat → evaporator starved → reduced capacity, coil warmer than ideal Where it’s measured: • Pressure at evaporator outlet / suction (to find Tsat) • Temperature on suction line near evaporator outlet (for actual temp)   Worked example... Show more

Superheat = actual suction line temperature − saturation temperature (from suction pressure for that refrigerant). It indicates how completely the refrigerant boiled off in the evaporator and helps protect the compressor from liquid floodback.
Why it matters:
• Too LOW superheat → risk of liquid entering compressor (floodback)
• Too HIGH superheat → evaporator starved → reduced capacity, coil warmer than ideal
Where it’s measured:
• Pressure at evaporator outlet / suction (to find Tsat)
• Temperature on suction line near evaporator outlet (for actual temp)
 

Worked example (calculation):
Suction pressure corresponds to Tsat 38°F. Suction line temp = 52°F.
Superheat = 52 − 38 = 14°F.

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