The heat pump draws in air through the evaporator coils, with a high powered fan. Freon liquid inside the coils absorbs the heat from the drawn in air, changing the Freon liquid into a warm gas.

The gas in then passed through a compressor, which reduces the volume of gas, while increasing its temperature. This compressed (hot) gas is then pumped through the outer casing of the heat exchanger, where it releases its heat to the pool or spa water passing through the inner casing of the heat exchanger.

The warm water is passed to the pool or spa for recirculation until the desired temperature is achieved. The Freon gas returns to a liquid state and is pumped back through the system to repeat the cycle.