Pros and Cons of Condensing Boilers
A condensing boiler has one great upside: it’s the most energy efficient boiler around.
They are more efficient because they use two heat exchangers (which take the heat from the burning of the fuel and passes it into the water), as opposed to one used in conventional boilers. The second heat exchanger in a condensing boiler captures the heat in the flue gases.
The flue gases are a product of the initial and main combustion process, and are usually allowed to escape into the atmosphere. With the condensing boiler, it re-uses this flue gas energy to increase the boiler efficiency by up to 15%.
And this greater efficiency leads to the boilers great pro: less fuel (reduced costs) and less carbon dioxide (better for the environment).
So, if they are that efficient, why is every boiler not a condensing boiler? Simply, the extra efficiency causes its own problems.
And here come the cons.
Firstly, the by-product of capturing the exhaust gases is a large amount of liquid which has to be removed from the boiler using pipes and drains. Basically water, it is corrosive to the boiler and must be handled safely. And no matter how good the wastage system, there will still be droplets of water around the base of the flue, meaning that some thought has to given to where it is installed, so as not to endanger a building, or annoy a neighbour.
Secondly, the flue cannot work as with a conventional boiler, as the vapour is too cool to escape by itself and a fan has to be installed to help with the extraction.
Thirdly, you have the expense of not only a second heat exchanger, but one that, because of the lower temperatures involved, has to be larger.
All this requires extra cost and therein lies the difficulty with condensing boilers. They may well be more efficient, but the cost savings as weighed against the purchase price, does put a lot of people off. And manufacturers, striving to make their equipment even more efficient, sometimes struggle to justify this cost, even though over say a period of two years the savings made by using a condensing boiler will repay the extra initial outlay.
Apart from the second heat exchanger and water waste system, the boiler is much the same as a conventional example, including its control system, so operating it on a day-today basis is little different. They might be a little more expensive to install, but service costs should be roughly the same as well.
And a condenser boiler sits comfortably with modern day central heating systems, and there’s no need to change radiator sizes, or pipework.
The question comes down to whether you think having a boiler which operates at 90% efficiency, rather than 70%, is worth the initial higher outlay. In the running of such a boiler, it will burn less fuel and be better for the environment, but, does that justify the higher purchase price?
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