EPA Section 608 Universal Certification ExamType II (High-Pressure Appliances)Hard
A technician is preparing to recover refrigerant from a high-pressure appliance and is concerned about protecting the vacuum pump from contamination. Which of the following is the MOST effective method to prevent oil contamination of the vacuum pump during system evacuation?
- ARunning the vacuum pump for an extended period to boil off contaminants.
- BUsing a recovery machine to remove as much refrigerant as possible before evacuating.
- CConnecting a moisture indicator to the vacuum pump intake.
- DChanging the vacuum pump oil regularly.
Show answer & explanationAnswer & explanation
Correct answer: B. Using a recovery machine to remove as much refrigerant as possible before evacuating.
The primary contaminants that can damage a vacuum pump are liquid refrigerant and oil from the system. By using a recovery machine to remove as much refrigerant (both liquid and vapor) as possible, the technician minimizes the amount of liquid refrigerant and entrained oil that could enter and contaminate the vacuum pump. This is a crucial step before initiating deep vacuum for dehydration.
Why the other options are wrong
- A. Running the pump for an extended period might eventually boil off some moisture, but it doesn't prevent initial liquid refrigerant or oil contamination of the pump's oil, which can damage the pump.
- C. A moisture indicator detects moisture, but doesn't prevent contamination of the pump oil itself.
- D. Regular oil changes are good maintenance but don't prevent initial contamination from the system.
Vacuum Pump Protection
Measures taken to shield a vacuum pump from contaminants like liquid refrigerant, oil, and moisture during the evacuation process.
- Liquid refrigerant and oil are major contaminants.
- Thorough refrigerant recovery is the best defense.
- Using a vacuum pump with a gas ballast helps with moisture.
Memory trick: First, recover all the gas, then the vacuum pump will last!