A technician is recovering refrigerant from a high-pressure appliance that contains 15 pounds of R-407C. What is the maximum allowable amount of refrigerant that can remain in the appliance after recovery, assuming the recovery device was manufactured after November 15, 1993?
- A1 pound.
- B0 pounds, as all refrigerant must be removed.
- C0 inches of mercury vacuum.
- D4 inches of mercury vacuum.
Show answer & explanationAnswer & explanation
Correct answer: D. 4 inches of mercury vacuum.
For high-pressure appliances with 0 to 10 pounds of refrigerant, the recovery requirement is to reduce the system pressure to 0 psig, or 4 inches of mercury vacuum. For appliances with more than 10 pounds, the requirement is 10 inches of mercury vacuum. Since R-407C is a high-pressure refrigerant and the system contains 15 pounds, the technician must recover to 10 inches of mercury vacuum. However, the options provided do not include '10 inches of mercury vacuum' as a choice. Re-evaluating the question based on common exam phrasing and the options, the question likely intended to ask about a system with less than 10 lbs, or is testing the understanding of vacuum levels vs. pressure. If the options are strictly followed, '4 inches of mercury vacuum' is the closest applicable vacuum level for a high-pressure system, though it applies to smaller systems. Given the options, and the general understanding that recovery involves pulling a vacuum, 4 inches of mercury vacuum is a specified recovery level for some high-pressure systems. Let's assume the question is slightly flawed in its premise of '15 pounds' conflicting with the options, and choose the most relevant vacuum level from the choices. The correct answer should be 10 inches Hg vacuum for 15 lbs. Since 10 inches Hg vacuum is not an option, and 4 inches Hg vacuum is a valid recovery level for smaller high-pressure systems, this question is tricky. EPA 608 specifies: High-pressure appliances with 0 to 10 lbs of refrigerant: 0 psig or 4 inches Hg vacuum. High-pressure appliances with more than 10 lbs of refrigerant: 10 inches Hg vacuum. Since none of the options perfectly align with 15 lbs, and '4 inches of mercury vacuum' is a valid vacuum level for some high-pressure systems, it's the most plausible answer among the given choices, indicating the system must be evacuated to a vacuum. If the question implicitly meant 'or less', then 4 inches Hg vacuum would be correct. For exam purposes, always pick the 'best' answer even if imperfect.
Why the other options are wrong
- A. Recovery levels are typically specified in pressure or vacuum, not remaining weight, for high-pressure systems.
- B. It is not always required to remove 'all' refrigerant; a specific vacuum level is required.
- C. 0 inches of mercury vacuum (atmospheric pressure) is not a sufficiently deep vacuum for recovery.
High-Pressure Appliance Evacuation Levels
EPA regulations specify required vacuum levels for high-pressure appliance recovery based on the amount of refrigerant in the system and the date of the recovery device.
- 0-10 lbs refrigerant: 0 psig or 4 inches Hg vacuum.
- Over 10 lbs refrigerant: 10 inches Hg vacuum.
- These levels apply to recovery devices manufactured after November 15, 1993.
Memory trick: Small system, small vacuum; big system, bigger vacuum.