EPA Section 608 Universal Certification ExamType III (Low-Pressure Appliances)Medium
A low-pressure chiller requires a new heat exchanger. Before opening the system for this component replacement, what is the critical step to prevent air and moisture contamination?
- APressurize the system to 20 psig with nitrogen.
- BFlush the system with a solvent to remove any residual oil.
- CEvacuate the entire system to a deep vacuum of 500 microns.
- DIsolate the section of the system containing the heat exchanger and recover refrigerant.
Show answer & explanationAnswer & explanation
Correct answer: D. Isolate the section of the system containing the heat exchanger and recover refrigerant.
Before opening any part of a refrigeration system, especially one containing refrigerant, the refrigerant must first be recovered. Isolating the specific section minimizes the amount of refrigerant to recover and prevents widespread contamination.
Why the other options are wrong
- A. Pressurizing with nitrogen before recovery would mix nitrogen with refrigerant, making recovery less efficient and contaminating the refrigerant.
- B. Flushing is a separate procedure for cleaning and occurs after refrigerant recovery and often after major repairs, not as the first step before opening.
- C. Evacuation occurs after recovery and repairs, not before opening a system that still contains refrigerant.
System Opening Precaution
Before opening a low-pressure refrigeration system for service, all refrigerant must be recovered from the section to be opened to prevent release and minimize air/moisture contamination.
- Recover refrigerant first.
- Isolate the section if possible.
- Prevents release of refrigerant.
- Prevents air/moisture entry.
Memory trick: Before you open the 'door' to the chiller, make sure the 'air' inside is gone.