Your pool water is circulated through the heater by the pool pump and gathers the generated heat from the heater in the unit's heat exchanger. A fluid inside of the heat pump is in a closed system that is not exposed to atmosphere. A refrigerant such as Freon or a similar chlorofluoro hydrocarbon is circulated through this loop. This fluid is compressed by the compressor and when this warm gas is compressed it concentrates that heat of the fluid. At this point that heat is transferred from the compressed fluid to the water via a heat exchanger, which is essentially a set of tubes with the hot fluid on the inside and the cool water on the outside. At this point, the two fluids try to reach a temperature equilibrium where the pool water is heated and the heat exchanger's fluid is cooled. Upon exiting the heat exchanger, the refrigerated passes through an expansion valve and returns to the low pressure side of the system. While this fluid is under low pressure, it passes through the evaporator coils and cooling fans of the system to remove the cold air via a fan. At this point the refrigerant again starts to cycle through the system and gain heat through the compression process.

Heat pump pool heaters use either scroll compressors or reciprocal compressors. The scroll compressors are more efficient in their operation and are found in higher efficiency heat pumps.

Heat pump pool heaters use more energy in their operation when the ambient temperature is lower. However, when the outside air temperature is 50° or higher they will be able to operate in an efficient manner. This is generally not a consideration for most pool owners since they only utilize their swimming pools during the warmer weather.

Although heat pump pool heaters for above ground swimming pools have a higher initial cost than gas pool heaters, their operating costs are much lower due to their increased efficiency. Generally, they will produce five dollars worth of heat for each dollar of electricity used. Additionally, heat pump pool heaters generally last 10 years or more and have a usable lifetime that is about two times greater than the life of the average gas fired pool heating unit.

The repair guy came out and fixed my swimming pool heater. He told me to keep it running for the next couple of days while it breaks in. The problem is that my pool filter system is old and is a piece of crap and I have to keep restarting it. So can anybody tell me if I can turn off the pump and just let the heater run?