A2L Specific Service Procedures 2

Question 1

When performing a standing pressure test on an A2L system, what gas must be used?

Accepted Answer

Dry nitrogen — never pressurize with oxygen, air, or refrigerant for testing

Answer

The A2L refrigerant itself

Answer

Compressed air from a shop compressor

Answer

CO2 from a fire extinguisher

Question 2

What is the minimum evacuation (vacuum) level required before charging an A2L system?

Accepted Answer

Typically 500 microns (0.5 mm Hg) or below, held for a specified time, per manufacturer requirements

Answer

Any vacuum is sufficient

Answer

Zero gauge pressure

Answer

Atmospheric pressure

Question 3

After brazing a repair on an A2L system, what tests must be performed before recharging?

Accepted Answer

Pressure test with nitrogen to verify the repair is leak-free, then evacuate to 500 microns to remove moisture, then leak test all connections before charging

Answer

Just visual inspection of the braze joint

Answer

Charge immediately and test during operation

Answer

Only test if the system won't cool

Question 4

How should a technician handle an A2L system that has been contaminated with moisture?

Accepted Answer

Recover all refrigerant, replace the filter-drier, perform a triple evacuation with nitrogen breaks, and recharge with fresh refrigerant

Answer

Add a filter-drier and run the system

Answer

Just evacuate for an extra hour

Answer

Moisture doesn't affect A2L systems

Question 5

What is the correct method for checking an A2L system's superheat?

Accepted Answer

Same method as R-410A, but for A2L BLENDS, use the dew point (not boiling point) for the saturation temperature at suction pressure

Answer

No different from R-410A — measure suction line temperature and suction pressure, then calculate

Answer

Superheat doesn't apply to A2L systems

Answer

Only subcooling matters for A2L

Question 6

A system has both R-410A and R-454B versions available. The existing linesets are copper. Can R-454B be used with the existing copper tubing?

Accepted Answer

Yes — R-454B is compatible with standard copper tubing, though line sizes may need to match the new system's specifications

Answer

No — R-454B requires special alloy tubing

Answer

Only if the copper is type L

Answer

Copper must be replaced with stainless steel for A2L