There are four basic types of pool heating systems. These are Solar, Gas, Electric Heat Pumps and Electric Element. The best system for your pool is determined by numerous factors including your needs, desires, budget and physical location of the pool and house. Your location in Australia will also play a significant part of this decision, as our varying weather patterns and differing energy pricing structures by State do influence the overall equation.
We provide some brief commentary on the role of solar collector and electric element heaters in pool heating below but understandably, our focus and area of most expertise is in heat pump and gas.
Solar Pool Heating
Solar pool heating is extremely popular because of its obvious advantage in using free energy from the sun.
Solar heating systems work by direct heat transfer. The water from your pool is circulated through the collector, which is usually located on a roof. Most systems utilise a digital controller, which sends water to the roof whenever there is sufficient sunshine, provided that the pool is not already at the desired temperature.
Solar heating is perfect for those recreational pool owners looking for a heating system that has minimal operating cost and which provides a warm pool when people most want to swim. That is, on fine summer days. After the initial installation cost, the only additional expense is the operation of the booster pump (which most manufacturers recommend). Because of its reliance on weather conditions, the solar system will provide a consistency of temperature in summer and a variable temperature rise at the edges of the season in late Spring and early Autumn.
When considering the installation of a solar heater, the all-important factors are the collector area proposed, collector design and quality of material. There is only a fixed rate at which the sun will provide energy, so the larger the collector the more heat will be gained. As a general rule the collector should be equal to at least 80% of the area of the pool, although 100% coverage would be more typical. Results improve as the collector size is increased. Other points that are important when considering solar are the pitch and directional aspect of the roof, that is, which way it faces. A roof facing north is most favourable because it will receive the maximum amount of sunlight. Any shading of the roof by large trees will also be considered. The location of the pool and how much it is affected by shade and wind is also important.
Electric element heaters are purpose built and provide a low purchase cost option, which is compact and easily installed.
Element heating works much like an electric kettle in that there is a direct heat transfer between the immersed element and the pool water. The small physical size of the units makes them ideal for use where plant space is at a premium or where gas supply is not available and the special installation needs of a heat pump cannot be met. Element heaters will operate at a slightly higher cost to gas if connection is made to the overnight off peak tariff.
Electric Heat Pump
The electric heat pump is sometimes called a "solar heat pump" because of its unique ability to capture heat value from air temperature and turn this to water heating at high efficiency. In essence, these units are for those pool owners who want to swim most, if not all, of the year.
Heat pumps work like a reversed air conditioner. Instead of taking air from a room or building, removing the heat and returning it, a heat pump takes large quantities of air from the atmosphere, the heat contained in the air is removed and transferred to water from the pool or spa passing through the unit.
The characteristic of the heat pump of absorbing heat value from air means that the unit has a low electrical input relative to its heat transfer. Heat pumps output heat at a rate of around 5:1, relative to their energy input. This greatly reduces total energy consumption. This factor is called the heat pump's co-efficient of performance or COP. The capture of solar energy from air means that the heat pump's output and efficiency will vary with air temperature. Higher efficiency is gained in more temperate locations but heat pumps are capable of maintaining pool temperatures year-round in nearly all areas of Australia.
Combined with their high-energy efficiency, heat pumps are ideal for connection to off peak or time-of-use electricity pricing, as is becoming more available through the introduction of digital or smart meters. Where off-peak or time-of-use electricity pricing options are available, heat pumps become the lowest operating cost system for extended season or year-round heating.
Gas heaters are used in large numbers on pools and spas and give great flexibility to the pool owner, because of their rapid heating ability and robustness.
Gas heaters can easily maintain any desired water temperature as typical sizing is based on providing heater capacity capable of achieving a 14°C rise in water temperature in 24 hours. This allows a cold pool to be heated to a beautiful 28°C - 30°C in around one day, even in winter. This heating strength makes gas perfectly suited for pools that are used for entertaining.
From the point of view of heating costs, the constant maintenance of pool temperature with gas is quite viable during the warmest months of the year. Whereas the solar heated pool will vary in temperature during this season, the gas-heated pool is maintained at the owner's preferred temperature. Gas heating costs will be modest, as the heating requirement of the pool is relatively low. Likewise, the gas heater owner has the added flexibility to heat for specific events such as birthday parties or BBQs, or for longer periods such as September school holidays.
A gas heater is ideally suited to be added to a solar system, as it will offset solar's inability to work at night or in poor weather.
The heating of a spa requires one of the powered forms of heating, that is, either gas, heat pump or element. The spa may be heated by a dedicated heater or by the pool heater, if the hydraulic design allows. Where a single heater is installed, there will be a need to alter valve settings to circulate the water between the spa and heater only, with the pool isolated while a fast temperature rise is achieved in the spa. The valve changeover and resetting can be done manually or by automated switching/valves.