Why must an idle low-pressure chiller usually be brought above atmospheric pressure before it is leak tested?
Leak detection · EPA 608 Type III. The correct answer, and the reasoning behind it.
Pressurizing low-pressure systems for leak tests, signs of leaks, inspections and reports.
The question
Why must an idle low-pressure chiller usually be brought above atmospheric pressure before it is leak tested?
- Leak detectors only work above 15 psig
- EPA requires every low-pressure leak test to be done at exactly 10 psig
- R-123 cannot be detected while it is a liquid
- Below atmosphere, leaks pull air in instead of pushing refrigerant outCorrect answer
Why “Below atmosphere, leaks pull air in instead of pushing refrigerant out” is correct
At room temperature an R-11 or R-123 chiller sits near or below atmospheric pressure. Any leak then draws air inward, so there is no refrigerant escaping for a detector or bubble solution to find. Raising the internal pressure slightly above atmosphere makes the leaks push refrigerant out where they can be located.
Source: EPA: Test Topics
Why the other answers are wrong
- Leak detectors only work above 15 psig — Detectors do not need 15 psig, and that pressure would be unsafe on a low-pressure chiller.
- EPA requires every low-pressure leak test to be done at exactly 10 psig — No rule sets a leak test pressure; 10 psig is a maximum, not a required value.
- R-123 cannot be detected while it is a liquid — The issue is the direction of flow through the leak, not the state of the refrigerant.
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