Whichever way you go about it Pool Heating is not a cheap exercise, so you need to make the right choices. As the character Alfred Lanning in ‘I Robot’ says “You have to ask the right question”, and that’s very important.
Direct sunlight heats a pool while evaporation cools a pool. There is some heat loss through the shell of a pool and when the ambient temperature is lower than the pool water temperature.
Where the pool is situated, the strength and quantity of the direct sunlight which strikes the pool and the ambient temperature will dictate which side (heating v’s cooling) wins. If a pool remains in full shade it will stay cool, even cold all summer. A pool in a high wind area will stay cooler than one that isn’t, which might be a welcome benefit in the middle of summer. A pool with a dark surface in a sheltered area in full sunlight may even get too warm in summer for some of us. The difference between pool temperature for similar pools in different locations can be up to 5 degrees Celsius.
This chemical works by reducing evaporation, by putting a thin film on the water surface. It works be reducing the quantity of top up water which is usually cold especially when you need to heat your pool. Conditions have to be near perfect for this to be of any real use.
According to the Office of Energy Efficiency and Renewable Energy which is an Office of the US Department of Energy – “Outdoor pools gain heat from the sun, absorbing 75%–85% of the solar energy striking the pool surface. This is an important contribution to the pool’s heating needs. A pool cover will decrease the solar gain contribution to some extent, depending on what type you use. A transparent bubble cover may reduce pool solar energy absorption by 5%–15%. A completely opaque cover will reduce it by 20%–40%. You need to consider this when selecting a pool cover.”
The same office also states that a pool cover will “reduce make-up water by 30% to 50%”. It is the prevention of heat loss due to evaporation (which is replaced by cold water) and the prevention of loss of pool heat overnight (due to the low ambient temperature) that make a pool cover a worthwhile investment, especially when used in conjunction with other forms of pool heating.
The type of pool cover that will best suit your heated pool will come down how long you have you pool uncovered during the day. If it is only uncovered for a couple of hours so you can have a swim then a bubble cover is the better choice as the pool can still get some benefit from direct sunlight heating without heat loss through evaporation. If you leave the heated pool uncovered all day then a thermal cover is the choice as it is more efficient at preventing heat loss to ambient temperature overnight. This is why you will see commercial and some apartment building pools using thermal blankets.
Running costs of a Heat Pump are cut in half when a cover is used overnight. This especially important if you heat your pool during the winter months, as heater running costs during winter are very expensive,
Back before the Boer War, Eskies and ice machines you would see canvas water bags hanging off radiators, barb wire fences, deck railings and so on. The water that came out of those bags was beautiful and cold – very refreshing.
How was that so?
The bags were wet, of course, and placed where there was air movement. The water would evaporate from the surface of the bag and that was the trick.
For water to change from the state of liquid water to water vapour, energy is needed for the water to make that change. That energy comes in the form of heat drawn from the water in the bag. Just like a breeze across your sweaty body cools you down, the water in the bags cooled down. Get this, it takes over five times the energy to convert water from liquid to gas as it does to heat the same amount of water from 00C to 1000C.
Above any body of water there sits a layer of water vapour. If nothing disturbs that vapour it will remain saturated and the volume of water in the pool will remain the same or close to it. As soon as you remove that vapour, more vapour will form, reducing the water in the pool and removing the energy in the form of heat that is required to make the change from water to vapour. Both water and heat are lost. A pool can loose up to 70% of its heat through evaporation.
During the day the heat will be replaced by heat from the sun while at night it will be lost if the ambient temperature of the air is lower than the pool water temperature.
Obviously, the biggest ally to water evaporation is wind across your pool.
Solar Heating will add a couple of extra months to the swimming season at each end.
How often do you get the urge to go for a swim in the pool you have spent all that money on when the warmer weather starts only to find out that the water is ‘freezing’?
The big advantage of a Gas Heater compared to other forms of heating is the ability to heat up a body of water quickly. This is ideal for a spa pool or a small plunge pool when you don’t use it very often. When you need to heat these pools for that special guest or a party night then this is the answer, especially if you are unlikely use that pool again for a few weeks.
A Gas Heater can also serve to kick-start you pool use if the pool is in full shade. Pools in full shade can take several weeks to heat up for the season (if at all).
If you are using the pool on a regular basis, say a daily swim or even hydrotherapy than a Heat pump is the more economical form of heating. Given the mess energy supply is in at the moment in Australia then a further question might be – “For how long?” Great care needs to be taken when selecting the right manufacturer to purchase from. You need to be certain that you are comparing oranges with oranges. There is no Australian Standard that requires manufacturers to present their heat pump information (CoP) in a standard format as is required in the USA. And that’s before you look at product quality. Coefficient of Performance (CoP) is used to compare the efficiency of different heat pumps. A CoP at 24 degrees Celsius doesn’t tell us very much. In Brisbane we need to know what the CoP is at 10 degrees Celsius because that’s when we want a heat pump to be efficient; when we need it to heat the pool.
Heat Pumps are like Air Conditioning Units. They heat water instead of air.
Like Air Conditioning Units, Heat Pumps move heat from one area to another or move cold from one area to another.
When heating, if there is plenty of heat in the area you want to take it from (that is, where the Heat Pump sits) then that will be easy and not expensive. It’s like running downhill. It doesn’t take a lot of energy. Even I can do that, with my good downhill CoP.
If the area is cool where you Heat Pump sits then a lot more work is required. It’s like running uphill. It takes a lot more energy, a lot more carbs. I catch a cab, thanks to my low uphill CoP. The steeper the hill, the greater the energy required until eventually the hill becomes too steep to run up. The colder the area you are trying to take heat from, the greater the energy (and dollars) that is required until eventually the area becomes too cold and no matter how much energy (and dollars) you put into it, you will not extract any more heat.
Let’s say we must sponsor an athlete for racing up hills. We must feed and take care of that athlete. Now we know that you need a good athlete (high CoP) to run up a steep hill. We also need to choose an athlete who will not pull a hammy, break a leg or have a heart attack. We don’t want an athlete who has expensive ‘special’ food requirements or one who will run up an expensive medical bill. We need to choose a quality athlete.
It’s the same when choosing a Heat Pump. We want a unit that will run efficiently at low temperatures that won’t cost a fortune in maintenance and will last.
It takes 4,180 joules of energy to heat 1 litre of water through 10C.
Heat pumps run for 20 hours and defrost for 4 hours.
Gas heaters run for 6 hours to produce the same result.
We need to compare COP (coefficient of performance) at 100C ambient temperature not 240C. We want to be able to make Make & Model unit performance comparisons during that time when the units have to work the hardest. They should all perform well at 24°C.
Night time temperatures rarely get below 90C in Brisbane in winter.
Water flow through Heat Pumps and Heat Exchangers (used with Commercial Gas Heaters) travels through titanium tubing. It does not matter what your pool chemistry is, this tubing will not corrode. You will usually get a 10 year warranty on the tubing in these equipment items.
Heaters where pool water comes into contact with metal compounds other than titanium are a different story altogether. Unless a pool has very sophisticated testing equipment installed along with constant monitoring of that equipment and frequent independent testing throughout the day, it is almost impossible to maintain correct chemical levels in a pool at all times. Many of the gas heaters and heating elements on the market contain corrosive metals which are especially sensitive to an incorrect pH level in the pool water. Check the warranty conditions before you purchase a heater. Many manufacturers will state that your warranty will be null and void if the pool chemistry is incorrect. You will be told that the reason your heater or heater element has failed is because the pool chemistry was incorrect. You can have some very good test records for your pool but you will still loose the argument. We have seen failure within 6 months and then the blame game starts. You can extend the life of these heaters by installing a pH controller but there are still many things that can go wrong. In saying that, there are Gas Heaters which have been operating for many, many years without any problems. These units had the technology to ensure a long life.
During our 15 years of operation we have not and will not install equipment where a manufacturer uses incorrect pool chemistry to void a warranty. We believe an item of pool equipment should be able to tolerate incorrect pool chemistry.
Pool Surface Area
Surface Colour as in ‘light’ or ‘dark’.
Wind across the pool
Percentage of shade throughout the period you want the pool heated
|“We have installed several of these units and to date they have performed as promised“
|“Both of these sites are large apartment buildings where we, at Adlers, did the installations. We are in touch with both sites and can state that the units are performing as promised.“
We will meet with you on site so that we can select the correct size heater and establish its intended location. We will quote an installed price and carry out the install once we have obtained the unit.