When topping off an operating system containing a blended refrigerant, what is the proper method?

When topping off an operating system containing a blended refrigerant, introducing the refrigerant as a liquid is the correct method. Blended refrigerants, which are mixtures of different compounds, have specific vapor-liquid characteristics that allow them to function properly in cooling systems.

Filling a system with blended refrigerants in vapor form can disturb the composition of the refrigerant mixture, leading to inefficiencies, reduced cooling performance, or even damage to the system. The vaporization of the refrigerant in the system could cause the lighter components to escape faster than the heavier components, altering the intended performance characteristics of the refrigerant blend.

When refrigerant is introduced as a liquid, it helps maintain the proper ratio of components within the blend, ensuring optimal performance of the cooling system. This method also allows the refrigerant to absorb heat more effectively as it enters the low-pressure side of the system, leading to a more efficient operation.

Therefore, for maintaining system integrity and performance, adding the blended refrigerant as a liquid is essential.