Why does a leak in a low-pressure chiller make the purge unit work harder?

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 does a leak in a low-pressure chiller make the purge unit work harder?

• ARefrigerant escaping out through the leak forces the purge to make up the loss
• BThe leak lowers the oil level, starving the purge pump
• CThe leak raises evaporator pressure above atmospheric
• DAir drawn in through the leak collects as noncondensables to be purgedCorrect answer

Why “Air drawn in through the leak collects as noncondensables to be purged” is correct

Air and moisture enter wherever the machine is below atmospheric pressure. The air does not condense, so it gathers in the condenser and the purge unit must remove it. The more air that leaks in, the more often the purge runs.

Source: EPA: Test Topics

Why the other answers are wrong

• Refrigerant escaping out through the leak forces the purge to make up the loss — The purge handles noncondensables entering the machine, not refrigerant escaping it.
• The leak lowers the oil level, starving the purge pump — The purge unit does not depend on the chiller oil level.
• The leak raises evaporator pressure above atmospheric — A leak into a vacuum side does not raise the evaporator above atmosphere.

Practice more of this

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