Why might a technician add a trace amount of R-22 to the nitrogen used to pressure test a system?
Leak detection · EPA 608 Type II. The correct answer, and the reasoning behind it.
Signs of leaks in high-pressure systems and leak testing before charging.
The question
Why might a technician add a trace amount of R-22 to the nitrogen used to pressure test a system?
- So an electronic leak detector can sense the escaping gasCorrect answer
- To lubricate the compressor during the test
- To raise the test pressure without using any more nitrogen
- To dry out moisture inside the system
Why “So an electronic leak detector can sense the escaping gas” is correct
Electronic leak detectors respond to halogenated refrigerants, not to nitrogen. A small trace of R-22 in the nitrogen lets the detector find where the test gas escapes while keeping refrigerant use low.
Source: EPA: Test Topics
Why the other answers are wrong
- To lubricate the compressor during the test — A trace of refrigerant does not lubricate the compressor.
- To raise the test pressure without using any more nitrogen — The amount is too small to matter for pressure; nitrogen supplies the pressure.
- To dry out moisture inside the system — R-22 does not dry the system; evacuation removes moisture.
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