Pool heating - insiders discuss the best pool heating options for your clients
Even the most basic pools are a luxury item. So for clients who have decided to invest in a pool, it doesn’t make sense to limit its use to the warmer months while having to maintain cold water that no one can enjoy for the rest of the year. With the range of pool heating options available there is a pool heating solution to suit every pool and budget. Pool+Spa discusses the current pool heating options and trends with industry insiders.
With the state swimming pool registers slowly becoming operational there will hopefully be accurate data on Australia’s swimming pools in the near future, but until then, there is little reliable data available.
Published in January, 2006, BIS Shrapnel published its inaugural report entitled ‘Backyard Swimming Pools in Australia: An Analysis, 2005’. The primary objective of this study was to provide a comprehensive analysis of backyard swimming pools in Australia, based on pool owner feedback. The pool owner data was the result of a targeted national telephone survey of 747 pool owners, undertaken in early December 2005. The results from this survey revealed that just 33% of in-ground pools and just 10% of above-ground pools were heated. Further to this, the survey revealed that 28% of all pool heating was solar, which translates into 90% of the pool heating market.
Based on these figures, it is clear that most pool owners are not taking advantage of the pool heating options available and of those who are, solar heating is the preferred choice.
Andy Chan from Solartherm International believes that one of the most efficient ways to utilise energy from the sun is to heat water. “There are a lot of similarities of solar hot water (SHW) systems and solar pool heating (SPH) systems. The two main differences are that SHW heats a small body of water by a large temperature rise (ie, 300 L up to 65°C) and SPH heats a large body of water by a small temperature rise (ie, 50,000 L to 26°C).
“The other main difference is that SHW’s body of water is in an enclosed tank and SPH is an open body of water. Being an open body of water, SPH is subject to greater effects from weather conditions (ie, heat loss from wind, drop in ambient overnight temperature). The heat loss from these weather conditions can be greater minimised by installing a pool blanket,” said Chan.
Solar panels heat pool water when the water is recirculated from the pool through the solar panels by a booster pump. The solar panels absorb the solar energy from the sun into the water and return the heated water back to the pool, thus raising the pool temperature. A specially designed solar controller attached to the pump keeps the pool at the desired temperature in a cost-effective manner.
According to Chan, “The amount of energy required to raise 1 litre of water by 1°C is 3.96 BTU. For example, to raise a 50,000 L pool by 2°C would require 396,000 BTUs, which equates to approximately 116 kWh. The current Tariff 11 rate in Queensland is approximately $0.25 per kWh. This equates to $29 in energy required. A 2°C rise in pool temperature over the course of a sunny day is easily achievable for a solar pool heating system and costs far less than $29.”
John Dixon, National Sales Manager at Sunbather Pool Technologies says, “Solar pool heating is the people’s choice due to concerns of future fossil fuel costs. Solar pool heating is simple to install; doesn’t require additional trades, ie, electricians and gas fitters; solar pool heating has a longer life and warranty, cheaper set-up costs, minimal running costs and allows swimming when the weather is warm enough to entice the swimmer.”
Michael Mansfield from Leisure Coast and Double Bay Solar also backs solar pool heating. “Where pools cannot be solar heated, gas would be preferred if you want to swim all year round. However, for the warmer months solar or a heat pump will heat your pool most efficiently.”
Robert Sterland, Product Manager at Pentair Australia, recommends a combination of gas and solar, with a dedicated automation system. “This way you can make the most of what the sun provides but lets you extend your pool season and heat your spa to comfortable temperatures using the gas heater. The pool automation system, such as an IntelliTouch, just takes the hassle out of it, allowing you to change the heat source and set the temperature with the press of a button - not to mention the luxury of turning the spa on with an app on your iPhone on the way home from work.”
But solar does have its limitations. “One of the limitations of solar pool heating is that it is obviously weather dependent. The amount of radiant heat from the sun can vary dramatically depending on cloud and wind. Cloud and wind will also affect the natural temperature of the pool. This means that if the pool itself is shaded by cloud, it will not be exposed to the natural heat from the sun that it would be when there is no cloud,” added Chan.
Some pool suppliers would suggest other methods as a first preference. Jonathan Bristow of Zodiac Group Australia suggests heat pumps as a first choice. “Heat pumps are best for all-year heating and for those that want to swim whenever they feel like it. They are very energy efficient for this purpose; the down side is it can take a few days to heat the pool (depending on the size) but they maintain the heat very efficiently. But if you want to swim every now and then, so basically heat on demand, a gas heater is the way to go. Gas heat gives a very powerful and quick way to heat water, but they are expensive to run all the time.
“We have noticed a shift towards heat pumps because of the low running costs of all-year heating. Some are choosing this over solar for a few reasons, such as that you get all-year heating (even in subzero climates) - they provide heat even when there is no sun,” added Bristow.
Heat pumps were developed in the 1970s when two engineers were seeking a solution to heat a pool at a fraction of the cost of a conventional gas heater. But it has only been in the past five years or so that heat pump technology has significantly evolved - and Australian pool owners have begun to realise the countless benefits.
“In that time there has been a number of key developments in heat pumps,” says Bryan Goh from Waterco, whose heat pump division has been manufacturing heat pumps since 1986. “Major enhancements have been the lowering of noise levels; enhanced, higher efficiency ozone-friendly refrigerant; and greater durability.”
Heat pumps work like a reverse-cycle air conditioner by extracting ambient heat from the atmosphere, which is then transferred to the pool water. A highly efficient, low-cost option, heat pumps come in a number of different sizes ranging from 2 to 200 kW output. And compared with gas heaters, heat pumps can save you up to 80% over LPG and 50% over natural gas.
Simon Boadle, Director at Sunbather Pool Technologies, believes that the use of heat pumps when heating pools should only be an option when the use of solar heating is not viable. “Heat pumps are great consumers of electricity (and contributors to greenhouse gas emissions) and are often the most expensive appliance in the house to run.
“The only reason heat pumps - being used for pool heating - are not being targeted by DCCEE in their recent E3 Energy Efficiency program for more control of peak electricity load conditions is that the installed base numbers are currently insignificant. This was verified by Dr George Wilkenfeld at an E3 discussion meeting held in Melbourne on April 5. In our opinion, it is only a matter of time before the low greenhouse gas alternative of solar is legislated as being the preferred heating system and that stand-alone heat pumps can only be used where the use of solar is impractical,” said Boadle.
In October 2012, a number of Private Certifiers in NSW and Queensland were interpreting the Heating Provisions within the Building Code of Australia stating that, “Heat Pumps and Gas Heaters are no longer a legal form of heating for domestic swimming pools due to the fact that the Building code of Australia Volume 2 (for class 1 and 10 buildings), section 22.214.171.124 (a) states ‘heating for a swimming pool other than a spa pool must be by a solar heater, not boosted by electric resistance heating’.”
This interpretation was being picked up by other private certifiers across other parts of Australia causing significant confusion and concern.
Together, state SPASAs logged a submission to the Australian Building Codes Board Committee to amend clause 3.12.57. Following consideration, the Australian Building Codes Board Committee supported the changes and has amended the clause. It now allows additional types of heating for swimming pools to be included in the public comment draft of Volume Two (Residential) of the National Construction Code 2014.
“People should be able to heat their pools using heat pumps, gas heaters or even geothermal - the standard was poorly written and nonsensical. I think the changes, as proposed, to the standard are sensible and mandating the use of a pool cover will make the most out of any pool heating system,” said Sterland.
Heating commercial pools
Then, of course, there’s heating for commercial pools. Adam Shelley, Solar and Heating Manager at Zane, recommends the use of combined technology. “Gas boilers have been the preferred practical method of heating larger commercial pools; however, with gas costs rising plus concerns about carbon emissions, there has been growing focus on solar and heat pumps.
“When the efficiencies are compared, the difference between gas boilers and heat pumps is dramatic. Gas heater input to output efficiency ratios are less than 1:1, whereas a heat pump may deliver efficiencies in the range of 1:3 to 1:6. A high-efficiency heat pump on the optimal electricity tariff may save the commercial pool owner significant energy costs by switching to commercial heat pumps.
“Many commercial-sized pools are assessing their energy use and their options, and there are moves toward heat pumps and solar and combined technologies, where each heat source is programmed to run under optimal conditions.
“Detailed energy flow analysis conducted by Zane/Waterco on commercial-scale pools often identifies ways to save a significant amount of energy, while providing a more comfortable environment for the swimmers,” added Shelley.
What’s next for pool heating?
New emerging technologies include glazed solar collectors and hybrid spa heating systems combining heat pumps and electric heaters. Industry leaders are responding to customers’ needs to conserve energy while having the convenience of automation. The market now has more choice with the increased popularity of control systems, which can be used to manage pool heaters - especially heating combinations, such as gas and solar.
“All existing heaters are working close to their efficiency limits. Pool design and the more effective use of pool covers offer the greatest area for the development of new technologies,” says Boadle.
Except for an old solar standard, there are currently no standards on the measurement of performance or efficiency of pool heating equipment in Australia. “Waterco would like to see performance standards introduced so that all pool heating equipment can be measured equally to create a level playing field in Australia. This would also provide consumers with correct information for comparisons for use in their buying decisions. Eg, heat pump coefficients under standardised conditions and solar performance and sizing,” said Shelley.
Regardless of how your clients choose to heat their pool, “The emphasis should be put on heat retention rather than heat generation ie, covers. It makes greater economic sense,” said Boadle. Be sure to read the pool covers feature in the September/October edition of Pool+Spa.
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