In the push-pull method of liquid recovery from a large R-22 system, what does the recovery machine do?
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
In the push-pull method of liquid recovery from a large R-22 system, what does the recovery machine do?
- It pumps liquid directly through its compressor
- It moves vapor from the cylinder into the system to push liquid outCorrect answer
- It heats the system so the liquid boils over into the recovery cylinder
- It runs the system's own compressor to pump down
Why “It moves vapor from the cylinder into the system to push liquid out” is correct
In push-pull, the machine draws vapor off the recovery cylinder, lowering its pressure, and pushes that vapor into the appliance. The pressure difference pushes liquid from the appliance into the cylinder.
Source: EPA: Test Topics
Why the other answers are wrong
- It pumps liquid directly through its compressor — Push-pull keeps liquid out of the machine's compressor.
- It heats the system so the liquid boils over into the recovery cylinder — Heating is a separate way to speed recovery.
- It runs the system's own compressor to pump down — Using the system's compressor is system-dependent recovery, not push-pull.
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