What is the function of a 4-way reversing valve in a heat pump?

The function of a 4-way reversing valve in a heat pump is to redirect refrigerant flows between heating and cooling modes. This valve allows the heat pump to switch between absorbing heat from the outside air to heat a space (heating mode) and releasing heat to the outside air to cool a space (cooling mode).

In heating mode, the reversing valve changes the direction of the refrigerant so that it flows from the compressor to the indoor coil, where it releases heat, and from the outdoor coil to the compressor, where it absorbs heat from the outside environment. In cooling mode, the flow of refrigerant is reversed, enabling the system to absorb heat from the indoor space and expel it outdoors. This flexibility is essential for the dual function of heat pumps, providing efficient heating during cold weather and cooling when temperatures rise, making the 4-way reversing valve a critical component in managing the operation of heat pumps.