What should the state of the refrigerant be in the suction line?

The correct state of the refrigerant in the suction line should be a low pressure, low temperature vapor. In a typical air conditioning system, the refrigerant absorbs heat from the indoor air as it passes through the evaporator coil. This heat transfer process lowers the pressure of the refrigerant, turning it into a vapor while also reducing its temperature, especially as it absorbs heat in the evaporator.

The low pressure condition is essential as it allows the refrigerant to effectively draw in heat from the surroundings, which is necessary for the refrigeration cycle to continue. A low temperature is also critical because it maximizes the refrigerant's ability to absorb heat, enhancing the overall efficiency of the cooling process.

In contrast, the other states mentioned would not function correctly in the suction line. For instance, high pressure vapor would indicate that the refrigerant is not able to efficiently absorb heat, potentially leading to compressor damage, while low pressure, high temperature vapor would suggest that the refrigerant has not properly absorbed sufficient heat, potentially leading to inadequate cooling. High pressure, low temperature liquid would indicate that the refrigerant is in the liquid state, which is not desirable in the suction line as it needs to be vapor to ensure proper compressor operation and prevent liquid slugging.