A residential split air conditioning system containing R-410A is found to be 2.5 kg undercharged from its nominal 5.0 kg charge. What is the recommended method for adding refrigerant to ensure proper system performance and oil return?

Question: A residential split air conditioning system containing R-410A is found to be 2.5 kg undercharged from its nominal 5.0 kg charge. What is the recommended method for adding refrigerant to ensure proper system performance and oil return?

Answer options:

• Add refrigerant as a vapour to the low-pressure side until the charge is correct.
• Add refrigerant as a liquid to the high-pressure side during operation. ✅ Add refrigerant as a liquid to the low-pressure side slowly, ensuring it flashes to vapour before entering the compressor.
• Add refrigerant as a liquid to the suction line while the compressor is off, then start the system.

Correct answer: Add refrigerant as a liquid to the low-pressure side slowly, ensuring it flashes to vapour before entering the compressor.

Explanation: R-410A is a zeotropic blend, and to maintain its composition, it must be charged as a liquid. Charging it into the low-pressure side as a liquid is acceptable, provided it flashes to vapour before reaching the compressor to prevent liquid slugging and potential damage.