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Condensing Boilers

If there’s one technology that’s currently dominating modern-day boiler manufacturing, it’s condensing, or what’s also labelled high efficiency.

And although this breakthrough came many years ago, it’s only now, in this period of global warming and eco-awareness, that condensing boilers have taken off.

It’s fair to say that most boilers today – when using a combustible fuel – make use of condensing technology. And it’s this which allows boilers to reach plus 90% levels of efficiency, whereas in the pre-second world war years, boilers would struggle to get returns of 50%. In other words, say a bucket of coal was thrown on a fire, half of it would disappear up the chimney and only half the heat would be used for the home.

Modern boilers nowadays have to reach at least band B on the SEDBUK scale. Band B means between 86% to 90% efficiency, but most boilers should ideally be rated within band A (90% efficient and over). The Building Regulations state that if a property can accommodate a band B, or A boiler, then one has to be fitted. The only real exception are back boilers which tend to be the only appropriate unit for certain cottages and terrace houses.

Basically a simple process, condensing is all about taking a double grab at the heat generated by the combustion of the fuel type. Most of the heat is of course produced by, lets say, a burning gas flame, but a large proportion is obviously locked in the exhaust gases. But if that can also be harnessed, then the units efficiency will rise.

Which is why condensing boilers have two heat exchanges which should, ideally, be from high grade stainless steel for maximum performance and reliability. One heat exchanger takes the heat from the flames, the other from the exhaust gases.

It is a great technology and has alone allowed boilers to make dramatic leaps forward in terms of efficiency levels, in a time of increasing energy concerns.

The downside of a condensing boiler is a practical consideration. The process of collecting the exhaust gases requires the boiler designer to consider two side effects. One, a liquid (condensate) is produced during the process and two, the exhaust gases, once exploited for their heat, need help escaping the flue (chimney).

So, a modern condensing boiler has to be fitted with a drain system to remove the condensate (causing siting issues and extra cost installing the drain) and a fan has to be fitted inside the flue to ensure the safe removal of the gases (extra cost again).

And the condensate drain had one unfortunate side effect when sited on an external wall; it can freeze in cold weather which causes the boiler to shut down. So a frost protection feature for a boiler is very important.

Condensing technology is here to stay and will improve even further over the coming years.

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