In the heat mode, what does the suction line entering the compressor contain?

In the heat mode of a heat pump, the suction line entering the compressor contains low-pressure refrigerant gas. This is because, during the heating cycle, the refrigerant absorbs heat from the outside air (even in cold conditions) and evaporates in the evaporator coil. As it absorbs heat, the refrigerant changes from a liquid state to a gas, resulting in low-pressure refrigerant gas in the suction line.

The compressor's role is to increase the pressure and temperature of this low-pressure gas before it moves to the condenser. Understanding this cycle is crucial, as it explains how the heat pump efficiently transfers heat from the outside to the inside of a building, even when the outside temperature is low. In contrast, other choices refer to different phases of the refrigerant cycle and would not accurately describe the contents of the suction line entering the compressor in heat mode.