RSES Refrigerant Management 4 — Questions and Answers
Question 1: What is the minimum required vacuum level (in microns) that most equipment manufacturers specify before charging a system with refrigerant?
- 500 microns (Correct answer)
- 1000 microns
- 2000 microns
- 5000 microns
Correct answer: 500 microns
Most manufacturers require evacuation to 500 microns or lower to ensure adequate moisture removal and verify system integrity before charging.
Question 2: A certified technician may purchase refrigerants in containers larger than 2 lbs without restriction under Section 608. What document proves this certification?
- State contractor license
- EPA Section 608 technician certification card (Correct answer)
- OSHA 10-hour card
- Manufacturer training certificate
Correct answer: EPA Section 608 technician certification card
EPA Section 608 requires technicians to hold a valid certification card issued by an EPA-approved certifying organization to purchase refrigerants in containers over 2 lbs.
Question 3: During refrigerant recovery, the vapor recovery method is generally slower than liquid recovery. In which situation is vapor-only recovery typically used?
- Large systems with more than 200 lbs of refrigerant
- Small systems or when liquid access is not available (Correct answer)
- Systems using zeotropic blends only
- Systems with flooded evaporators
Correct answer: Small systems or when liquid access is not available
Vapor recovery is typically used on small systems or when the service valve configuration doesn't allow direct liquid removal from the system.
Question 4: Refrigerant R-744 is the designation for which natural refrigerant that is being increasingly used in transcritical refrigeration systems?
- Ammonia (NH₃)
- Propane (C₃H₈)
- Carbon dioxide (CO₂) (Correct answer)
- Water (H₂O)
Correct answer: Carbon dioxide (CO₂)
R-744 is carbon dioxide (CO₂), which has a GWP of 1 and is used in transcritical refrigeration systems particularly in food retail and industrial applications.
Question 5: What action must a technician take if they discover a refrigerant leak rate exceeding the EPA threshold in an appliance with more than 50 lbs of refrigerant?
- Immediately evacuate the building
- Repair the leak within 30 days or develop a retrofit/retirement plan within 30 days (Correct answer)
- Add refrigerant to compensate for the loss and document it
- Notify the EPA within 24 hours
Correct answer: Repair the leak within 30 days or develop a retrofit/retirement plan within 30 days
EPA Section 608 requires that leaks exceeding threshold rates in large appliances be repaired within 30 days of discovery, or a retrofit/retirement plan must be developed within 30 days.
Question 6: Which of the following refrigerants has an ASHRAE safety classification of A2L, indicating it is mildly flammable?
- R-134a
- R-410A
- R-32 (Correct answer)
- R-22
Correct answer: R-32
R-32 is classified A2L by ASHRAE, meaning it has low toxicity (A) and is mildly flammable with a low burning velocity (2L).
Question 7: What is the purpose of performing a standing vacuum test after evacuating a refrigeration system?
- To verify the refrigerant charge is correct
- To check for system leaks and verify the vacuum holds before charging (Correct answer)
- To test the operation of the expansion valve
- To measure the system's cooling capacity
Correct answer: To check for system leaks and verify the vacuum holds before charging
A standing vacuum test involves isolating the system after evacuation and monitoring the micron gauge; a rising vacuum level indicates a leak or residual moisture.
RSES Refrigerant Management 4
What is the minimum required vacuum level (in microns) that most equipment manufacturers specify before charging a system with refrigerant?