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Condensing boilers

Since 2005 changes have been made to meet carbon emission targets. All new gas-fired boilers must be high-efficiency condensing boilers.

In a conventional boiler, fuel is burnt producing hot gases which are used to heat water in the heat exchanger. One of the gases produced is steam. A lot of the heat energy inside this steam is lost out of the flue to atmosphere. Effectively you are paying to heat the air outside your home. Condensing boilers recover the latent heat in this steam by converting it back to water. This increases the efficiency of your boiler by as much as 10 to 12%. Flue gases from a combi are much cooler. Typically 55 degrees celcius compared to around 180 coming from a conventional type boiler. Consider carefully where your flue is sited. Pluming from a boiler flue can be a nuisance to your neighbours.

When do condensing boilers work best?

Condensing boilers are at their most efficient when they are in condensing mode, but unfortunately this only occurs during a short time of the heat up period when the return temperature is around 55 degrees celcius. The efficiency of the boiler will decrease as the temperature of the return increases above this point. However, a condensing boiler will still offer more efficiency over a non-condensing boiler during the complete heat-up and cool-down cycle.

It is not true that condensing boilers are only efficient when in fully condensing mode.

Energy Agency
Due to its larger heat exchanger, a condensing boiler does not have to condense in order to be more efficient.Typically a new gas condensing boiler will have a seasonal efficiency of between 84% and 92% compared with a new non-condensing boiler at 78% or an older boiler at 55-65%.

You will need to connect a condensing boiler to a drain. It is important that your plumber follows building regulation guidance in setting this pipework out to mitigate the risk of freezing which will stop your boiler from working at the time when you most need it.

The government’s Boiler Scrappage Scheme has now issued all of the money allocated to stimulate the industry and raise awareness of energy efficiency. An A-rated boiler could save as much as £235 a year in gas. Visit the Energy Saving Trust to find out more.

Confused about what this all means and would like some free and friendly advice? Please call us on 07867 937389 and we will be happy to pop over and discuss your requirements.

Want to learn about other types of boiler? Read our page on combi boilers.