Condensing Boilers

Condensing Boilers

Condensing Boilers

As we move closer and closer to running out of gas here in the UK and around the world, technology is moving with us. Since April 2009, it has been a requirement in the UK to only fit high efficiency gas boilers when a gas appliance is being used to heat hot water or provide space heating.

To enable us to reach the dizzy heights of the strict efficiency controls, manufacturers developed on the existing condensing technologies which were already in existence and improved them somewhat, until we got to a point where condensing really is now as close as we’re going to get for maximum efficiency from a burnt fossil fuel.

With boilers now hitting efficiency ratings around the 90% mark and beyond, something that was unheard of only a few years ago, the industry has greatly changed and although we’re never likely to hit the 100% efficiency mark with gas, the greenies have been working hard and we’re starting to see appliances being produced that can even exceed 100% efficiency, but more on them for another day.

Today I want to share some knowledge around the condensing technology. There’s plenty of myths that I encounter on a daily basis and huge chasms within people’s own knowledge that need filling. A condensing boiler is now the “normal” boiler that you’d have installed, they come in both the combination and system type variants (Where you’d have a tank and airing cupboard) as well as “heat-only” models. They work by effectively transferring more heat into the central heating system by either a secondary heat exchanger (The bit that converts heat from gas flames to that in the water) or by using incredibly tightly wound drum exchangers that simply slow the products of combustion (The fumes that go out of the flue) down to enough that the majority of heat can be utilised and induced into the heating water.

It wasn’t that long ago that you’d put your hand on a flue and get burnt by it’s temperature; these days you’ll find flues running at much lower temperatures, even down to around 55 degrees centigrade in some cases, so it’s more like putting your hand near bath water than facing a trip down A&E because your skin has melted.

One of the problems presented is the “plume”… Often referred to as smoke, when you drive down the road on a cold morning, especially around new-build estates you’ll see white smoke billowing out of all the houses. This is in effect what a condensing boiler does. It’s not toxic (Well, you wouldn’t want to breath it for prolonged periods) and is mainly made up of water vapour. When you burn gas and get the mixture between the fuel gas and air right, correct combustion will take place and the chemical reaction of the gas being burnt will produce water vapour. The fan will then expel these products and the vapour to outside, which is what that plume of white smoke is; it’s effectively just steam.

We get many complaints about the plume, but there’s not much we can really do apart from deflect it’s path. We use an array of techniques which include the “snorkel” like plume management kits (As pictured above for this article) to disperse the plume to areas where the plume is less likely to aggravate. With the older boilers, the combustion process was not as accurately performed and less water was produced, plus, with the much higher temperatures being expelled, the water vapour itself was often much further away and diluted to such a point that the plume was never normally visible.

Because of this production of water, condensing boilers will need a drain to get rid of excess water vapour. It’s quite corrosive so it’s essential that all the condense pipework is made of plastic. This can cause the most disruption when having an old boiler replaced with a new one as we need to get this excess water into a suitable drain. Where this is not possible, we can use small pumps to help us get the condense water to travel further in more imaginative ways to that drain. Of course, they come at a cost and do require a little maintenance.

All gas installers should now only be fitting condensing boilers unless very specific criteria can be met whereby it is simply not possible to get a suitable drain or manage the plume. If you’re looking to get a new boiler fitted and can meet the strict building regulation requirements for non-condensing appliances then you will obviously sacrifice the additional efficiency benefits found only in condensing boilers.

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