EPA Section 608 Universal Certification ExamType II (High-Pressure Appliances)Medium
A technician is using a vacuum pump to evacuate a high-pressure system after a component replacement. To prevent contamination of the vacuum pump's oil and ensure an effective evacuation, what should be done BEFORE starting the vacuum pump?
- ACharge the system with a small amount of refrigerant to flush out contaminants.
- BRecover any remaining refrigerant from the system.
- CPressurize the system with nitrogen to detect any leaks.
- DEnsure all service valves are closed to isolate the vacuum pump.
Show answer & explanationAnswer & explanation
Correct answer: B. Recover any remaining refrigerant from the system.
Before evacuating a system, any remaining refrigerant must be recovered. Starting a vacuum pump on a system with refrigerant still present will contaminate the pump's oil, reduce its effectiveness, and potentially damage the pump. This is a crucial step to protect the vacuum pump and ensure a successful evacuation.
Why the other options are wrong
- A. Charging with refrigerant before evacuation is incorrect and would contaminate the pump.
- C. Pressurizing with nitrogen for leak detection is a good step after repair, but recovery of refrigerant must precede evacuation.
- D. Service valves should be open to the system when evacuating, not closed.
Vacuum Pump Protection
To protect a vacuum pump and ensure effective evacuation, all refrigerant must be recovered from the system before the pump is started.
- Refrigerant will contaminate vacuum pump oil, reducing its effectiveness.
- Contaminated oil reduces the pump's ability to pull a deep vacuum.
- Regular oil changes are also important for vacuum pump maintenance.
Memory trick: No refrigerant in the pump, or your vacuum will get the hump!