Air Conditioning Repair Installation and Evacuation Procedures 3 — Questions and Answers
Question 1: What happens if a technician charges an AC system with non-condensable gases (such as air) still present?
- High-side pressure will be abnormally elevated (Correct answer)
- System will cool more efficiently
- Suction pressure will drop below normal
- Refrigerant will condense faster
Correct answer: High-side pressure will be abnormally elevated
Non-condensable gases raise head pressure above normal because they occupy condenser volume without condensing, reducing system efficiency and capacity.
Question 2: The recommended maximum lineset length without adding extra refrigerant charge for most mini-split systems is typically:
- 25 feet (pre-charged factory amount) (Correct answer)
- 100 feet
- 50 feet
- 10 feet
Correct answer: 25 feet (pre-charged factory amount)
Most mini-split systems are pre-charged at the factory for approximately 25 feet of lineset; additional refrigerant must be added for longer runs per manufacturer specs.
Question 3: Which type of copper tubing is required for ACR (Air Conditioning and Refrigeration) refrigerant line sets?
- Dehydrated, nitrogen-charged ACR copper tubing (Correct answer)
- Standard Type M plumbing copper
- Galvanized steel tubing
- CPVC plastic tubing
Correct answer: Dehydrated, nitrogen-charged ACR copper tubing
ACR-grade copper tubing is cleaned, dehydrated, and sealed with nitrogen to prevent moisture and contamination that would damage refrigerant systems.
Question 4: When insulating suction line tubing on an AC installation, the insulation must be:
- Continuous with no gaps, joints sealed, and of adequate wall thickness (Correct answer)
- Applied only at the outdoor unit connection
- Limited to areas exposed to direct sunlight only
- Installed over the liquid line only
Correct answer: Continuous with no gaps, joints sealed, and of adequate wall thickness
Suction line insulation must be continuous and fully sealed to prevent condensation, heat gain, and capacity loss throughout the entire lineset run.
Question 5: What is the primary reason technicians perform a nitrogen pressure test before evacuating a new AC system?
- To identify and locate leaks before pulling a vacuum (Correct answer)
- To purge contaminants from the lineset
- To pre-charge the system with nitrogen
- To test electrical connections under load
Correct answer: To identify and locate leaks before pulling a vacuum
Nitrogen pressure testing at 150–300 psig reveals leaks at joints and connections before the vacuum process, since a vacuum cannot identify leak locations.
Question 6: An outdoor condensing unit must be installed at least how far from the structure to ensure adequate airflow?
- Per manufacturer specifications, typically 12–18 inches minimum clearance (Correct answer)
- No clearance is required on any side
- At least 10 feet from the structure
- Only the discharge side needs clearance
Correct answer: Per manufacturer specifications, typically 12–18 inches minimum clearance
Manufacturers specify minimum clearances (commonly 12–18 inches on sides) to ensure adequate airflow and prevent hot discharge air recirculation.
Question 7: When brazing copper refrigerant lines, nitrogen should be flowing through the tubing during the brazing process to:
- Prevent oxidation (scaling) inside the copper tubing (Correct answer)
- Speed up the cooling process after brazing
- Increase braze filler flow rate
- Purge refrigerant oil from the line
Correct answer: Prevent oxidation (scaling) inside the copper tubing
Flowing dry nitrogen through copper tubing during brazing displaces oxygen, preventing copper oxide scale formation that could contaminate the refrigerant system.
Air Conditioning Repair Installation and Evacuation Procedures 3
What happens if a technician charges an AC system with non-condensable gases (such as air) still present?