The benefits of stainless steel heat exchangers are widely known in the domestic boiler market. Just like your cutlery, they are incredibly resistant to corrosion, which is important when water is constantly flowing through them. And that means you’ll get a good lifespan out of them.
However, not everyone is aware of the benefits of aluminium heat exchangers, even though they have been used since the 1970s in Europe. At Ideal Boilers, we’ve used aluminium heat exchangers for over 30 years, the first model using an aluminium condensing heat exchanger being the Ideal Turbo launched in 1986. Today, the award-winning Logic, Logic+ and Logic Max range all utilise an aluminium heat exchanger. Here are the main benefits:
1. Thermal Conductivity
Aluminium has a very high thermal conductivity (237W/m²/K). In layperson’s terms, that means that they warm up very quickly and allow heat to pass through them efficiently. In other words, you’re not wasting heat by warming up the heat exchanger for a long time. If you’ve ever filled a hot water bottle, it can be surprising how cool it can feel at first, even when it’s just been filled with piping hot water. But the heat does get through eventually. If it were made of aluminium rather than rubber, it would warm up much quicker – but might not be quite as comfortable under your feet!
So thermal conductivity is a material’s ability to transfer heat. In the case of a boiler, this is the heat from the combustion gases to the system water flowing through the central heating and hot water systems. Because of this high thermal conductivity, we have been able to design a heat exchanger that needs less surface area. This allows us to produce more compact, lightweight boiler designs.
2. Giving new life to old systems
Aluminium heat exchangers are more tolerant to variable system quality (e.g. flow rate settings, air and dirt) than are stainless steel designs, as they allow for bigger waterways (which brings more benefits, as we’ll see later). This means that they are well suited for a boiler replacement on an old system. The aluminium heat exchanger developed by Ideal Boilers will allow for a wider range of temperature differentials, typically 11–20 °C, meaning that the aluminium heat exchanger is perfect for older systems that are unable to reach a 20 °C differential without making system modifications.
3. Noise, what noise?
Because the waterways in aluminium heat exchangers are much larger, as we discussed earlier, the water velocity can be greatly reduced because a greater volume can pass through the heat exchanger with less obstruction. Not only does this reduce hydraulic resistance through the heat exchanger, it also reduces the noise created by water flow rates.
In fact, the Logic+ and Logic Max Combi have both been awarded the Quiet Mark award for such low noise levels. That’s really important if your boiler is somewhere close to where you spend most of your time, or even if you want to listen to the radio when you’re cooking and your boiler is in the kitchen. Also, any noise means energy is being wasted somewhere, so a smoother flow with less sound could also be a sign that you’re running a more efficient boiler.
4. Corrosion Resistance
On contact with water or oxygen, a non-porous protective layer of aluminium oxide is formed naturally: this is alumina, or the passivation layer. It’s why aluminium ladders and car bodywork can look like new after years of use.
This chemical reaction contributes to the heat exchangers in the Ideal Logic, Logic+ and Logic Max boilers being highly resistant to the corrosion effects of condensate during operation.
Both stainless steel and aluminium have anti-corroding qualities, but work in slightly different ways at the molecular level. However, it’s just not true that aluminium heat exchangers are more susceptible to corrosion – we wouldn’t use them if they were.
5. They’re less expensive, too
Aluminium heat exchangers are also considerably less expensive than stainless steel ones. It’s the most abundant metal on earth – in fact, it’s the third most abundant element after oxygen and silicon – and it’s also easily recycled. It all adds up to a much less expensive material than stainless steel, which requires an energy-intensive manufacturing process.
6. It’s light
Although probably not the most important factor, having a lighter heat exchanger certainly won’t do you any harm. As well as being light to transport, it makes it easier to install, and if you’re having your boiler wall-mounted, as many people do, you’ll put a bit less strain on your wall and any supporting brackets.
Go with the flow: choose aluminium
So there we have six good reasons why aluminium heat exchangers are an excellent choice. We’re not saying there’s anything wrong with stainless steel, we use stainless steel in some of our boilers but if you’re wary about aluminium, we hope we’ve put your mind at rest.