When charging a refrigerant system, in what state should the refrigerant be added?

When charging a refrigerant system, the refrigerant should be added in a liquid state. This is because liquid refrigerant can efficiently fill the evaporator coil, and it allows for a controlled and consistent charge. When the refrigerant enters the evaporator as a liquid, it easily evaporates and absorbs heat in the coil, which is crucial for the refrigeration cycle to function effectively.

Adding refrigerant as a vapor, while it may seem viable in certain situations, often leads to a less efficient charging process. Vapor does not provide the same level of cooling as liquid; it displaces less volume and may not fill the system adequately. Additionally, adding refrigerant in a mist form would be inefficient for proper system performance, as it would not adequately facilitate heat transfer.

Using a gaseous form would also prevent the system from adequately circulating the refrigerant, making it difficult to maintain the necessary pressures and temperatures within the system components. Therefore, introducing the refrigerant as a liquid is essential for achieving optimal operation and efficiency of the HVAC system.