A technician is preparing to recover refrigerant from a high-pressure appliance that has a charge of 30 pounds. The recovery unit being used has a listed maximum allowable working pressure (MAWP) of 300 psig. Which of the following conditions would prevent the technician from using this specific recovery unit?
- AThe refrigerant is R-410A.
- BThe saturated vapor pressure of the refrigerant at 100°F is 350 psig.
- CThe system pressure is 150 psig.
- DThe ambient temperature is 70°F.
Show answer & explanationAnswer & explanation
Correct answer: B. The saturated vapor pressure of the refrigerant at 100°F is 350 psig.
Recovery equipment must be able to handle the pressures of the refrigerant being recovered. The MAWP of the recovery unit (300 psig) must be greater than or equal to the maximum expected system pressure, which can be estimated by the refrigerant's saturated vapor pressure at the highest ambient temperature it might encounter. If the saturated vapor pressure of the refrigerant at 100°F (a common maximum ambient temperature for equipment rating) is 350 psig, and the recovery unit's MAWP is only 300 psig, then the unit is not rated for the pressures it could potentially face, making it unsafe and unsuitable for use.
Why the other options are wrong
- A. R-410A is a high-pressure refrigerant, but its mere presence does not prevent recovery unless its pressure exceeds the unit's MAWP.
- C. A system pressure of 150 psig is below the recovery unit's MAWP of 300 psig, so this would not prevent its use.
- D. An ambient temperature of 70°F is well within normal operating ranges and would not inherently prevent recovery.
Recovery Unit MAWP Matching
The maximum allowable working pressure (MAWP) of a refrigerant recovery unit must always be equal to or greater than the highest expected pressure of the refrigerant being recovered, typically considering its saturated vapor pressure at 100°F.
- MAWP must exceed refrigerant's max pressure.
- Consider saturated vapor pressure at high ambient temps (e.g., 100°F).
- Ensures safe and compliant operation.
Memory trick: MAWP must always overpower the refrigerant's highest pressure punch.