Near the end of recovering vapor from an R-22 system, recovery slows down. Why?

Recovery techniques · EPA 608 Type II. The correct answer, and the reasoning behind it.

Recovering liquid first, speeding recovery, and avoiding cross-contamination.

The question

Near the end of recovering vapor from an R-22 system, recovery slows down. Why?

• AThe recovery cylinder is getting colder
• BLower system pressure means thinner vapor, so less moves per strokeCorrect answer
• CThe machine's filter-drier has clogged and stopped flow almost entirely
• DThe oil is turning into vapor

Why “Lower system pressure means thinner vapor, so less moves per stroke” is correct

As the system pressure drops, the vapor becomes less dense, so each pump stroke moves less refrigerant. The pressure difference also shrinks as the cylinder fills, so the final stage is the slowest.

Source: EPA: Test Topics

Why the other answers are wrong

• The recovery cylinder is getting colder — A colder cylinder would speed recovery, not slow it.
• The machine's filter-drier has clogged and stopped flow almost entirely — A working filter does not usually explain the normal slowdown.
• The oil is turning into vapor — Oil does not turn into vapor in recovery.

Practice more of this

More EPA 608 Type II practice questions, or see every EPA 608 practice test.