EPA Section 608 Universal Certification ExamType II (High-Pressure Appliances)Hard
A technician is considering using a system-dependent (passive) recovery method for a high-pressure appliance containing R-410A. Which of the following conditions would make this method impractical or ineffective?
- AThe system has a large amount of liquid refrigerant.
- BThe ambient temperature is high (e.g., 90°F).
- CThe recovery cylinder is significantly colder than the system.
- DThe system has a significant non-condensable content.
Show answer & explanationAnswer & explanation
Correct answer: D. The system has a significant non-condensable content.
System-dependent recovery relies on the pressure differential between the system and the recovery cylinder. If the system contains a significant amount of non-condensables (like air), these will increase the system pressure and reduce the pressure differential, making it difficult or impossible to transfer refrigerant using a passive method.
Why the other options are wrong
- A. A large amount of liquid refrigerant can actually speed up passive recovery initially, as liquid flows more easily than vapor.
- B. High ambient temperature generally increases system pressure, which would aid, not hinder, system-dependent recovery by increasing the pressure differential.
- C. A colder recovery cylinder creates a larger pressure differential, which would improve, not hinder, system-dependent recovery.
System-Dependent Recovery Impairments
Factors that can render system-dependent (passive) recovery ineffective or impractical, primarily by reducing the necessary pressure differential.
- Low system pressure makes passive recovery ineffective.
- Presence of non-condensables increases system pressure, impeding recovery.
- Passive recovery cannot achieve deep vacuum levels.
- Ambient temperature affects system pressure and thus recovery rate.
Memory trick: Passive problems: LOW pressure, HIGH non-condensables.