EPA 608 609 System Evacuation and Charging Procedures 1 — Questions and Answers
Question 1: What is the primary purpose of evacuating a refrigeration system before charging with refrigerant?
- To pre-cool the system
- To remove moisture and non-condensable gases (Correct answer)
- To test for refrigerant leaks
- To purge the remaining old refrigerant
Correct answer: To remove moisture and non-condensable gases
Evacuation removes moisture and non-condensable gases such as air and nitrogen that would degrade system performance and damage components.
Question 2: What instrument is used to measure the depth of vacuum during system evacuation?
- Manifold gauge set
- Micron gauge (electronic vacuum gauge) (Correct answer)
- Thermometer
- Refrigerant identifier
Correct answer: Micron gauge (electronic vacuum gauge)
An electronic micron gauge measures vacuum in microns of mercury (µmHg), providing accurate readings below the range of standard manifold gauges.
Question 3: What vacuum level in microns must be achieved before charging most residential HVAC systems per industry standards?
- 500 microns (Correct answer)
- 1,000 microns
- 2,000 microns
- 5,000 microns
Correct answer: 500 microns
AHRI and most manufacturers specify that systems must be evacuated to 500 microns or below before refrigerant charging to ensure adequate moisture removal.
Question 4: What should a technician investigate if the vacuum rises rapidly above 1,000 microns immediately after isolating the vacuum pump?
- Begin charging immediately since the pump is done
- Add more compressor oil to the system
- A system leak or residual moisture (Correct answer)
- Run the vacuum pump for an additional hour
Correct answer: A system leak or residual moisture
A rapid rise in micron level after isolation indicates either a leak allowing air entry or moisture still boiling off inside the system.
Question 5: Why should a technician evacuate from both the high and low sides of a refrigeration system?
- To increase system operating pressure
- To achieve faster and more thorough evacuation past any closed internal valves (Correct answer)
- Because DOT requires dual-port evacuation
- To measure superheat from both sides simultaneously
Correct answer: To achieve faster and more thorough evacuation past any closed internal valves
Evacuating from both service ports removes non-condensables and moisture more quickly and ensures no section of the system is isolated from the vacuum.
Question 6: What type of oil must be used in vacuum pumps designed for HVAC/R refrigerant work?
- SAE 30 motor oil
- Standard mineral oil
- Dedicated vacuum pump oil (Correct answer)
- Synthetic compressor oil
Correct answer: Dedicated vacuum pump oil
Vacuum pump oil is specially formulated to maintain low vapor pressure and absorb moisture without breaking down, which standard lubricants cannot do.
EPA 608 609 System Evacuation and Charging Procedures 1
What is the primary purpose of evacuating a refrigeration system before charging with refrigerant?