Pool Heating & Dehumidification Heat Pump
Pool heating heat pumps use the vapor compression cycle to extract heat from the air for heating swimming pools or spas. Pool heating heat pumps must be constructed of special materials to resist corrosion. High-quality models incorporate coated evaporator coils, cupro-nickel heat exchangers, and corrosion-resistant cabinets specifically designed for pool environments. Pool heating heat pumps may be designed for outdoor or indoor installation.
Pool heating heat pumps operate in a single mode for heating. In outdoor installation, the cooling effect is generally not utilized and is dissipated. In indoor installations the pool heating heat pump can provide some dehumidification and cooling. During winter this cooling effect may be unwanted.
Pool Heating and Dehumidification Heat Pump
Pool heating and dehumidification heat pumps are similar to pool heating heat pumps, but incorporate space cooling and dehumidification capabilities. Heat is used for heating the pool and, in some models, may also be used for space reheat as part of the dehumidification process. Units are designed for indoor or rooftop installation.
Pool heating and dehumidification heat pumps operate in several modes, with pool heating/dehumidification being the most common. Other operating modes such as air conditioning, space heating, or ventilation may require additional components.
Pool heating heat pumps operate in a single mode for heating. Common operating modes for pool heating and dehumidification heat pumps include:
- Pool heating with reheat - Heat and moisture are removed from the air inside the pool enclosure. A portion of the recovered heat is used for pool heating, the remainder is used to reheat the discharge air from the heat pump.
- Pool heating without reheat - Heat and moisture are removed from the air inside the pool enclosure. All the recovered heat is used for pool heating, creating a net cooling effect in the enclosure.
- Dehumidification - Heat and moisture are removed from the pool enclosure. All the recovered heat is used to reheat the leaving air. No pool heating is provided.
- Dedicated space cooling - Heat and moisture are removed from the air inside the pool enclosure. All of the recovered heat is rejected through an auxiliary condenser to provide space cooling. An auxiliary condenser is required if the pool and indoor air are not heated.
Ventilation - The refrigeration circuit is not utilized. Outdoor air is supplied to the pool enclosure. Exhaust of pool enclosure air may be provided. Some units offer expanded space conditioning or water heating capabilities using energy from auxiliary sources, such as chilled water systems or heating elements. Air-side economizers may be used for cooling. Additional operating modes include:
- Space cooling with economizer
- Space cooling with condenser (air-cooled and water cooled condensers are common options)
- Space cooling with auxiliary cooling (using chilled water coil)
- Space heating with auxiliary heat (electric resistance, hot water coil, steam coil, and fuel-fired furnaces)
- Supplemental water heating (using a second condenser or desuperheater)
Most pools in conditioned or partially conditioned spaces could benefit from the application of a heat pump to heat the pool and reduce humidity levels in the enclosure.
High HPWH run time is the key to successful heat pump water heater applications. High run time is achieved by applying a properly sized HPWH in facilities with significant water heating loads.
- Where there are large hot water consumption.
- Laundries and restaurants are common applications for HPWHs.
- Any facility which uses hot water and has a simultaneous need for additional space cooling and dehumidification.
- Where natural gas, liquid propane gas, oil, or electric resistance heat are expensive.
- Facilities where overheating and high humidity are serious problems.
- Residences with a source of waste heat, including basements, attics, and laundry rooms.
- Indoor spas
- Heat pump water heaters may be economically justifiable in outdoor pools under utility rates in many areas
Applications To Avoid
Applications with very short operating seasons may not provide adequate operating cost savings to justify the initial investment in a heat pump.
Because the required water temperature for pool heating is low, 80° F to 85° F, heat pump water heaters can operate with excellent efficiency. A COP of 3.5 to 6.5 is typical. For applications with indoor evaporators, the warm, humid air in the pool enclosure provides an excellent heat source for the heat pump. The high wet-bulb temperature and moderate dry-bulb temperature result in excellent operating efficiency and output.
There are no performance standards for pool heating heat pumps or pool heating and dehumidification heat pumps. A standard is being developed for pool heaters. ASHRAE 146P, Methods of Testing for Rating Pool Heaters will apply to all pool heaters, including gas-fired, oil-fired, electric resistance, and electric air-source heat pumps. The proposed standard is expected to be released in 1998.