EPA Section 608 Universal Certification ExamType I (Small Appliances)Medium
A technician is preparing to recover refrigerant from a small appliance. What is the maximum allowable pressure for a recovery cylinder containing mixed refrigerants?
- AThe pressure corresponding to the saturation pressure of the highest boiling point refrigerant at 130°F (54.4°C).
- BThe pressure corresponding to the saturation pressure of the highest boiling point refrigerant at 105°F (40.6°C).
- CThe pressure corresponding to the saturation pressure of the lowest boiling point refrigerant at 105°F (40.6°C).
- DThe pressure corresponding to the saturation pressure of the lowest boiling point refrigerant at 130°F (54.4°C).
Show answer & explanationAnswer & explanation
Correct answer: A. The pressure corresponding to the saturation pressure of the highest boiling point refrigerant at 130°F (54.4°C).
Recovery cylinders, especially those with mixed refrigerants, must not exceed a safe working pressure. This is determined by the highest possible pressure the mixture could reach, which is related to the highest boiling point component at an elevated temperature to account for potential heating.
Why the other options are wrong
- B. While using the highest boiling point refrigerant is correct, the 105°F temperature is not the appropriate upper limit for determining the maximum allowable pressure for a recovery cylinder for safety.
- C. Using the lowest boiling point refrigerant would result in an under-pressurized cylinder for a mixed refrigerant scenario, as other components would exert higher pressures. The 105°F temperature is also not the correct upper limit for this calculation.
- D. This option incorrectly combines the lowest boiling point refrigerant with the higher temperature, which would not accurately reflect the maximum pressure of a mixed refrigerant and could lead to an unsafe condition.
Mixed Refrigerant Recovery Cylinder Pressure Limit
When recovering mixed refrigerants, the recovery cylinder's maximum allowable pressure must be based on the saturation pressure of the highest boiling point refrigerant in the mix, at 130°F (54.4°C).
- Applies to cylinders containing mixed refrigerants.
- Uses the highest boiling point refrigerant as the reference.
- Calculated at 130°F (54.4°C) to account for elevated temperatures.
Memory trick: Highest boiling point, highest temperature, safest storage.