The heat pump has established itself as a viable product in the pool industry. Using a compressor, a refrigerant and an evaporator to cool the air, it essentially acts as an air conditioner.
The warm, humid climate of Florida has become the fastest-growing market for heat pumps. It’s estimated that approximately 50,000 units are being installed each year, with the vast majority sold in the Sunshine State.
Until recently, heat pumps have not been especially energy-efficient because that was not a critical factor in their design. Therefore, little effort was made to produce a heat pump with a high coefficient of performance.
But since the 1970s, people have become increasingly concerned about the cost of fuel. More and more nations work toward becoming self-sufficient in energy. The result has been a dramatic improvement in the efficiency and design of heat pumps. This has significantly increased performance.
How it works
A heat pump works by capturing heat in the air and transferring it to the pool water. Air temperature and humidity play important roles in creating a heat source. The more moisture in the air, the more heat the pump can extract.
The heat pump process begins by compressing and superheating the refrigerant. This superheated refrigerant moves through the heat exchanger and passes heat on to the swimming pool.
In refrigeration terms, the heat exchanger is the system’s condenser. As the refrigerant gas condenses into a liquid, it gives off most of the heat it has absorbed. After condensing and then releasing its heat into the pool water, the refrigerant passes through an expansion valve. This valve controls the flow of the refrigerant from the high-pressure side of the system into a low-pressure zone.
As the pressure is released, the refrigerant turns into a gas. As it expands into a gas, the refrigerant cools rapidly. The cool refrigerant is then circulated through the evaporator. The evaporator coils surround most or all of the surface areas, creating the main structure of the heat pump.
As the fan draws warm air across the evaporator coils, the cold refrigerant gas is pre-heated. It’s during this phase of the heat pump’s operation that “free” heat is captured. The warmer the air, the more heat the evaporator can absorb.
As the heat is drawn out, the moisture will change from its vapor form into a liquid. The liquid that is created during this process is called condensation. The condensation collects in the base of the heat pump, where drainage is provided to channel the water into a specific line or other suitable location.
Special features
For heat pumps to operate effectively in lower temperature climates, the refrigeration effect must be controlled sufficiently to prevent frost from building up on the evaporator coil. In most cases, this is accomplished by running the fan with the compressor shut down. The flow of air over the evaporator will remove the frost.
In areas where the temperature frequently drops below 55 degrees Fahrenheit, it is recommended to use models featuring hot-gas bypass. This feature reverses the flow of compressed refrigerant through the evaporator. The hot, compressed refrigerant gas quickly melts any accumulated frost and the heat pump can switch back to its normal mode, heating the pool.
The same feature used in cold weather also can be utilized by heat pumps to chill pools in the hottest climates. Operating a heat pump in the “chiller” mode keeps pools in hot climates refreshing. It also helps reduce the peak sanitizing loads often created by higher temperatures.
Picking your heat pump
Selecting the proper heat pump size is not as easy as picking the right natural gas or propane appliance. Because the ambient temperature plays such a critical role in a heat pump’s operation, the local weather must be taken into account to determine the correct heat pump capacity. Most major manufacturers have spent considerable time developing sizing software programs that help identify the proper model for specific regions and pools.
It’s important to remember that a heat pump works by using the surrounding air. Avoid installation locations that will restrict the flow of air around the unit. Keep in mind that a heat pump cools and expels chilled air. Locations that recirculate this chilled air around the unit operate far less efficiently than installations that provide unrestricted circulation of fresh air.
Exposure to direct sunlight also provides measurable heat absorption by the evaporator. A sunny, open area will work best in every case.