EPA Section 608 Universal Certification ExamType II (High-Pressure Appliances)Hard
A technician is evacuating a high-pressure system after a major component replacement. The goal is to dehydrate the system fully. Which of the following indicates that the system is properly dehydrated?
- AThe system pressure rises to atmospheric pressure after the vacuum pump is turned off.
- BThe system holds a deep vacuum (e.g., 500 microns or less) after the vacuum pump is isolated for several minutes.
- CThe vacuum gauge shows a steady pressure of 0 psig.
- DThe vacuum pump has been running for at least one hour.
Show answer & explanationAnswer & explanation
Correct answer: B. The system holds a deep vacuum (e.g., 500 microns or less) after the vacuum pump is isolated for several minutes.
Proper dehydration is achieved when the system holds a deep vacuum (typically 500 microns or less, which is 29.9 inches Hg vacuum) after the vacuum pump is isolated. If moisture is present, it will boil off and cause the vacuum pressure to rise as the pump is isolated, indicating incomplete dehydration.
Why the other options are wrong
- A. A rise to atmospheric pressure indicates a significant leak or incomplete evacuation, not proper dehydration.
- C. 0 psig is atmospheric pressure, not a vacuum, and indicates a lack of dehydration.
- D. Run time alone does not guarantee dehydration; the actual vacuum level must be measured.
System Dehydration Verification
The process of confirming that all moisture has been removed from a refrigeration system after evacuation.
- Achieved by pulling a deep vacuum (e.g., 500 microns or less).
- Verified by isolating the vacuum pump and observing a stable vacuum reading.
- Moisture presence causes the vacuum to rise after isolation.
Memory trick: Pull a deep vacuum, then hold it tight, for a system that's truly dry and bright!