Why does air get into R-11 and R-123 chillers when it does not get into an R-410A system?
Refrigeration · EPA 608 Type III. The correct answer, and the reasoning behind it.
Purge units and pressure-temperature behaviour of low-pressure refrigerants.
The question
Why does air get into R-11 and R-123 chillers when it does not get into an R-410A system?
- R-11 and R-123 absorb air from the oil and release it in the condenser
- Low-pressure chillers have no sealed joints
- Air is carried in with the chilled water
- Parts of the low-pressure chiller run below atmospheric pressureCorrect answer
Why “Parts of the low-pressure chiller run below atmospheric pressure” is correct
An R-410A system stays above atmospheric pressure everywhere, so leaks push refrigerant out. In a low-pressure chiller the evaporator and other parts run in a vacuum, so leaks pull outside air and moisture in.
Source: EPA: Test Topics
Why the other answers are wrong
- R-11 and R-123 absorb air from the oil and release it in the condenser — The refrigerant does not draw air out of the oil.
- Low-pressure chillers have no sealed joints — Chillers are sealed; air enters through leaks because of the pressure difference.
- Air is carried in with the chilled water — The water and refrigerant are separated by tube walls.
Practice more of this
More EPA 608 Type III practice questions, or see every EPA 608 practice test.
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