Frost on the suction line indicates what regarding temperature?

Frost forming on the suction line is an indication of specific temperature conditions. When frost appears, it generally suggests that the temperature of the suction line is below the dew point of the surrounding air. The presence of frost indicates that moisture in the air is condensing and then freezing onto the surface, which can only happen when the temperature of that surface is below the dew point.

In terms of temperature measurement, a suction line that is below the dew point will typically also fall below 32°F, the freezing point of water. Therefore, the correct answer highlights that the suction line temperature is indeed below both the dew point and 32°F.

This frost formation can be a signal of the system operating under specific conditions, potentially relating to cooling effects or issues such as low refrigerant levels, but it definitively denotes a temperature condition rather than indicating normal operation.