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What is a High Efficiency Condensing Boiler?

By David Holmes on July 2, 2009

In today’s modern world, we are often reminded about our impact on the environment with not just green charities and seemingly faddish green energy devices being thrust into our lives, but also the Government passing new laws and rules on how we consume energy in our homes. But, apart from the environmental benefits, why should you or I strive for higher energy efficiency – what are our bonuses for an often expensive choice?

The answer is in energy efficiency – the more efficient our boiler system is in our home, the cheaper our energy bills become, and with the steady rise in gas, oil and electricity prices we are all experiencing, investing in a boiler that is more efficient is the answer.

But what is a high efficiency condensing boiler – and how do they work?

The Basics

The condensing process that occurs on high efficiency condensing boilers are what gives them their name. Condensing occurs in the most efficient types of boilers, inside using a larger or a secondary heat exchanger – this means that more of the energy that is created by the boiler is extracted to the exchanger to heat the water while the boiler is in use, and reduces the amount of energy that is wasted. Normally, this heat would escape up the flue of an average boiler, but in a high efficiency condensing boiler the heat of the flue area is lower, reducing the temperature of the flue gases and producing condensate.

When it comes to energy efficiency, a high efficiency condensing boiler is the most efficient type of boiler available on the market today, converting more than 86% of all the fuel consumed into heat. Most conventional boilers only manage around 78%, with older boilers and back boilers managing even less.
High efficiency condensing boilers are not just efficient with their energy, but also in the amount of materials used in their construction, and ultimately, their size. Depending on the work-load of the boiler needed, the size will vary, but many will fit snugly into a standard kitchen cupboard space. This can be much smaller than many other boilers on the market, especially when you factor in the energy efficiency – a less efficient boiler may need to be larger to create the same output as a high efficiency condensing boiler.

Types of High Efficiency Condensing Boilers

There are three main different types of high efficiency condensing boilers on the market today, these include:

Regular Boilers
– A heat only or regular boiler provides hot water straight to your radiators. The system needs a storage cylinder for supplying hot water to taps and showers.
System Boilers – Requiring a separate hot water cylinder for storing heated hot water, but not requiring a roof tank like some types of boiler.
Combi Boilers – Requiring no tank, a combination boiler will heat up hot water on demand and circulate it where required. These are the most popular type of modern boiler, as they take up considerably less space.

What are the Negatives of a High Efficiency Condensing Boiler?

A high efficiency condensing boiler will suffer from an effect called ‘pluming’, which occurs in all types of condensing boilers. Pluming is a side effect of the condensing method, and looks like steam or gas escaping from the boiler and is much more noticeable in colder weather as it has an average temperature of 54°C. This plume of wet steam vapour will condense on a cold surface into small droplets of water, similar to when breathing on a window, and for this reason it is advised that all high efficiency condensing boilers are situated away from windows or cooler surfaces, as well as walls or internal corners where the damp may be trapped.