What does this most likely mean?

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

After evacuation the vacuum pump is valved off. The micron reading rises, then levels off and holds. What does this most likely mean?

• AThe vacuum is deep enough to charge
• BThe system has a large leak to the atmosphere
• CMoisture is still boiling off inside the systemCorrect answer
• DThe micron gauge has failed

Why “Moisture is still boiling off inside the system” is correct

A reading that rises and then levels off usually means moisture or refrigerant is still turning to vapor inside a tight system. A reading that keeps rising without leveling off suggests a leak. More evacuation is needed before charging.

Source: EPA: Test Topics

Why the other answers are wrong

• The vacuum is deep enough to charge — A significant rise shows the system is not yet dry.
• The system has a large leak to the atmosphere — A leak to the atmosphere keeps the reading rising instead of leveling off.
• The micron gauge has failed — A gauge that responds this way is working.

Practice more of this

More EPA 608 Core practice questions, or see every EPA 608 practice test.