EPA Section 608 Universal Certification ExamCoreMedium
A technician is evacuating a system after a major component replacement. To properly dehydrate the system, what vacuum level must be achieved and maintained, and what is the primary purpose of reaching this specific level?
- A750 microns; to confirm the system is leak-free.
- B250 microns; to ensure all non-condensable gases are removed.
- C1000 microns; to prevent oil contamination from the vacuum pump.
- D500 microns; to boil off and remove all moisture from the system.
Show answer & explanationAnswer & explanation
Correct answer: D. 500 microns; to boil off and remove all moisture from the system.
To properly dehydrate a system, a vacuum of 500 microns (or 500 millionths of a meter of mercury absolute) or lower must be achieved and maintained. At this low pressure, water boils at a very low temperature, effectively removing all moisture from the system.
Why the other options are wrong
- A. While a stable vacuum can help indicate a leak-free system, 750 microns is not deep enough for dehydration, and confirming leak-free status is a secondary benefit, not the primary purpose of this specific vacuum level for dehydration.
- B. While non-condensables are removed during evacuation, 250 microns is a deeper vacuum than typically required for dehydration and the primary purpose of 500 microns is moisture removal.
- C. 1000 microns is not deep enough for proper dehydration, and oil contamination is a separate issue related to proper vacuum pump operation.
Deep Vacuum Dehydration Level
To effectively remove moisture (dehydrate) from an HVAC/R system, a vacuum of 500 microns (0.5 mm Hg absolute) or lower must be achieved and maintained. At this low pressure, water boils at a low temperature and can be evacuated.
- Standard for proper dehydration.
- Removes both liquid and vapor moisture.
- Prevents acid formation and component damage.
Memory trick: Five hundred microns, water's gone, system's done.