Questions and Answers
What is superheat?
Vapor refrigerant heated above its saturation temperature.
Where in a refrigeration system can superheat be found?
Superheat can be found at the discharge line, outlet of the evaporator, suction line, and inlet of the compressor.
What is the recommended superheat reading for a thermal expansion valve (TEV) refrigerator system?
10-12 degrees of superheat is recommended for a refrigerator.
What is the recommended superheat reading for a thermal expansion valve (TEV) freezer system?
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What pressure gauge, on the gauge manifold, is used to calculate superheat?
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A superheat reading of 10F measured at the evaporator outlet indicates the refrigerant at that location is in what condition?
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A superheat reading of 0F measured at the evaporator outlet indicates the refrigerant at that location is in what condition?
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Would a 1 degree superheat reading on the suction line, at the compressor, be a recommended reading?
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An infrared thermometer is the best tool to measure superheat.
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A superheat reading indicates that there is liquid refrigerant at the location.
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What is subcooling?
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Name two places in a refrigeration system that subcooled liquid can be found?
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What pressure gauge is used to determine subcooling?
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When the refrigerant is saturated, what would be the subcooling measurement?
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If the saturation temperature at the liquid line is 100 F, and the actual liquid line temp is 90 F, how much subcooling is present?
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If there is 15 F of subcooling at the condenser outlet, the refrigerant must be in what state?
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Study Notes
Superheat
- Superheat refers to vapor refrigerant heated above its saturation temperature.
- Found in discharge line, outlet of the evaporator, suction line, and inlet of the compressor.
- Recommended superheat for thermal expansion valve (TEV) refrigerator systems is 10-12 degrees.
- Recommended superheat for TEV freezer systems is 4-6 degrees.
- Low pressure gauge (blue) on gauge manifold is used to calculate superheat.
- A measurement of 10°F superheat at the evaporator outlet indicates vapor (gas) refrigerant.
- A 0°F superheat reading at the evaporator outlet indicates saturated refrigerant (liquid and vapor).
- A 1°F superheat reading on the suction line at the compressor is not recommended, as it suggests the refrigerant is close to saturation.
- A contact thermometer is the proper tool for measuring superheat, not an infrared thermometer.
- Superheat indicates the presence of vapor refrigerant, not liquid refrigerant.
Subcooling
- Subcooling is liquid refrigerant cooled below its saturation temperature.
- Subcooled liquid can be found at the condenser outlet and in the liquid line.
- High side pressure gauge is used to determine subcooling.
- When refrigerant is saturated, the subcooling measurement is 0°F (zero).
- If the saturation temperature at the liquid line is 100°F and the actual liquid line temperature is 90°F, there is 10°F of subcooling.
- If there is 15°F of subcooling at the condenser outlet, the refrigerant is entirely in liquid state.
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Test your knowledge on superheat and subcooling concepts with these quick flashcards. Learn the definitions, applications, and recommended readings related to vapor refrigerants and refrigeration systems. Ideal for students and professionals in HVAC and refrigeration fields.
