In heating mode, what is the pressure condition of the refrigerant in the indoor coil?

In heating mode, the refrigerant in the indoor coil is under high pressure. This is because the heat pump system operates by extracting heat from the outside air (even when it's cold outside) and transferring that heat into the indoor space.

During the heating process, the refrigerant absorbs heat from the surrounding environment as it evaporates in the outdoor coil. It then moves indoors, where it is compressed by the compressor. This compression raises the refrigerant's pressure and temperature, allowing it to release the absorbed heat effectively when it enters the indoor coil. The indoor coil facilitates the transfer of this heat into the indoor air, providing warmth to the space.

As a result, in the indoor coil during heating mode, the refrigerant is indeed at a high-pressure state, which is essential for efficient heat transfer and system operation.