EPA Section 608 Universal Certification ExamCoreMedium
A technician is checking the superheat of a commercial refrigeration system. Which of the following is the correct calculation for determining superheat?
- ACondenser saturation temperature - Liquid line temperature
- BSuction line temperature - Evaporator saturation temperature
- CDischarge line temperature - Condenser saturation temperature
- DEvaporator saturation temperature - Suction line temperature
Show answer & explanationAnswer & explanation
Correct answer: B. Suction line temperature - Evaporator saturation temperature
Superheat is the difference between the actual temperature of the refrigerant vapor in the suction line (measured at the evaporator outlet) and its saturation temperature at the evaporator pressure. This value indicates if all liquid refrigerant has boiled off in the evaporator.
Why the other options are wrong
- A. This formula describes subcooling, not superheat.
- C. This represents the amount of superheat in the discharge line, but not the evaporator superheat which is crucial for system efficiency.
- D. This calculation would result in a negative value if superheat is present, as suction line temperature should be higher than saturation temperature for superheated vapor.
Superheat Calculation
Superheat is the difference between the actual temperature of the refrigerant vapor in the suction line (measured at the evaporator outlet) and the refrigerant's saturation temperature at the evaporator pressure.
- Indicates if all liquid refrigerant has boiled off in the evaporator.
- Proper superheat ensures the compressor only handles vapor.
- Too low superheat can lead to liquid slugging (compressor damage).
- Too high superheat indicates undercharge or inefficient evaporator.
Memory trick: Superheat: Suction temp MINUS saturation, vapor's extra heat.