Air left in a system after service is a non-condensable. What is a likely result?
Dehydration and evacuation · EPA 608 Core. The correct answer, and the reasoning behind it.
Evacuating to remove air and moisture at the end of service.
The question
Air left in a system after service is a non-condensable. What is a likely result?
- Lower discharge temperature
- Higher than normal head pressureCorrect answer
- Better heat transfer in the condenser
- A rise in the refrigerant's boiling point in the evaporator only
Why “Higher than normal head pressure” is correct
Air does not condense at system conditions. It collects in the condenser, takes up space needed for condensing and raises head pressure, which reduces capacity and puts extra load on the compressor.
Source: EPA: Test Topics
Why the other answers are wrong
- Lower discharge temperature — Non-condensables tend to raise, not lower, discharge temperature.
- Better heat transfer in the condenser — Air in the condenser reduces heat transfer.
- A rise in the refrigerant's boiling point in the evaporator only — The main effect is on the high side, where air collects.
Practice more of this
More EPA 608 Core practice questions, or see every EPA 608 practice test.
Unofficial, not affiliated with the EPA or any EPA-approved certifying organization. Questions are original practice written from public EPA material, not real exam questions.