Combination VS Condensing

What boiler technology do you need?

With all this boiler terminology flying around it’s no wonder most people come away with more questions than answers. And one of those questions is always, what is the difference between a combi and condensing boiler? It’s a simple enough question, and the answer is equally simple, there is no difference. So why the confusion?

The answer lies in the fact that combi and condensing boilers used to be separate technologies. If your boiler is more than 15 years old you likely have either a combi or a condensing boiler. But today all boilers, no matter if they are a combi, system or regular, are condensing boilers. In fact, it has been illegal to sell a non-condensing-gas boiler in the UK since April 1st 2005 – with oil boilers following in April 2007.

Despite this, many buyers are confused about what a condensing boiler actually is. So let’s look at the technology in more detail.

What is a condensing boiler?

A condensing boiler is an extremely efficient type of boiler which captures heat from the exhaust gases created during the combustion process, which otherwise would have been lost to the atmosphere. Heat is captured thanks to a Flue Gas Recovery System and used to preheat cool water as it enters the boiler, leaving the boiler with less work to do when reaching a desired water temperature.

How do condensing boilers work?

The process starts by super-cooling the hot exhaust gases created during combustion from around 130ºC to 50ºC. This causes the hot gas to condense back into water which then falls back to the bottom of the boiler. As it falls it passes over incoming pipes which return cold water from the heating system.

This preheats the returning water to around 40ºC, greatly reducing the amount of energy required to heat the water from cold. A modern efficient condensing boiler can create as much as two litres of condensate per hour and is up to 50% more efficient than a non-condensing boiler.

Condensing vs non-condensing boilers

To sum-up, a non-condensing boiler allows the hot gases created during the combustion process to escape through the flue. This wastes energy and means the cold water returning from the heating system needs to be heated again from scratch. This not only increases your energy bills it results in much higher CO2 emissions.

What is a combi boiler?

Now you know what a condensing boiler is, how do combi boilers fit into all this? A combi boiler is a type of gas boiler which provides both hot water and heating from a single unit. They are fed directly from the mains and heat water on demand so no header storage tank is required.

Combi boilers are considered the most efficient way of providing hot water and heating in an average-sized family home. How is this efficiency achieved? You guessed it, by using condensing technology. All combi boilers sold in the UK today have to use condensing technology by law. So a modern combi boiler is a type of condensing boiler.

Read our What is a Combi Boiler? article for more information.

Should you switch to a condensing combi boiler?

However, just because you have a combi boiler installed doesn’t mean you have a condensing combi boiler. Early combi boilers were non-condensing boilers which means they are not as efficient and waste energy. So if your boiler is more than 15 years old it’s worth checking to see if it uses condensing technology.

A tell-tale sign to look for is a plastic pipe (outdoors) leading from your boiler to a drain, this will be a condensate pipe which all condensing boilers have.

A modern condensing combi-boiler is around 25% more efficient than an old non-condensing type. So it is well worth considering swapping your old boiler out for a new one, even if it is still working reliably. In this scenario, replacing a non-condensing combi with a condensing one will help you to make significant savings on energy bills.

Read our Saving money with a new Combi Boiler? article for information on how a new combi could help you to save.

Conclusion

So there you have it, confusion over, all gas boilers sold since April 1st 2005 have to be condensing boilers by law. If your boiler is older than that, it may still be a condensing boiler, but it is worth checking.

If your boiler is not a condensing boiler then you should consider changing, their high efficiency output will not only help to shrink your energy bills but will also help to lower your carbon footprint.