As of 1st April 2005, any newly fitted gas-fired boiler in England or Wales has been a condensing boiler. Condensing boilers are modern and highly energy efficient. This article explains how they work and why they are so efficient, as well as how to go about getting funding to get your old boiler replaced.
How does a condensing boiler work?
A standard gas-fired boiler works by burning natural gas in order to heat up your radiators and hot water. When you burn natural gas, the chemical reaction that takes place produces water vapour and carbon dioxide as by-products. These warm waste gases will travel through a flue and escape into the outside atmosphere, taking some valuable heat with them. Conventional boilers vary in efficiency from around 65–75%, depending on their age and the type of boiler. This means that 35–25% of the energy they use is lost in the form of warm gas.
Condensing boilers are able to recover some of that heat that would usually be lost from the waste gases they give off. The waste gases travel through a heat exchanger, which cools and condenses them back into a liquid known as condensate. By doing this, it can recover some of the heat that would have otherwise been lost. The recovered heat is used to slightly warm up the cool water that returns from your radiators as it enters the boiler. A good condensing boiler can achieve an energy efficiency of over 90% plus.
The diagram below is a simplified version of what happens inside a condensing boiler.
Pros and cons of condensing boilers
If you are thinking about upgrading to a condensing boiler, the main thing to consider is the cost. This will depend on a number of factors, but the Energy Saving Trust indicates that a straightforward gas boiler replacement typically costs around £2,400. But before you get your wallet out, check if you can get it done for free, contact the local energy trust for more information.
Condensing boilers require an extra pipe to drain away the condensate liquid. Ideally, this pipe should connect to an internal drain. If this isn’t possible it can be drained externally. A small number of people with external condensate pipes have reported that they can freeze up in very cold weather — this can be prevented with pipe lagging. The condensate is also slightly acidic, so the pipe should be made of an appropriate material in order to prevent corrosion.
Other than the minor points mentioned above, condensing boilers are much more energy efficient and eco-friendly than their older counterparts.
How much money will I save?
This depends on the age and condition of your current boiler. For example, you won’t save a huge amount of money by upgrading from an 86% efficient to a 90% efficient boiler. You would, on the other hand, save a significant amount if you upgraded from a 70% to a 90% efficient one.
The table below shows the estimated savings you could achieve by upgrading to an A-rated energy efficient boiler. (The figures are estimates based on installing a new A-rated condensing boiler and a full set of heating controls in a gas-heated, semi-detached three bedroom house).
As you can see, if you have an old G-rated boiler (which most boilers fitted in 1998 or earlier are) you could reduce your energy bills by £310 a year.
Other Ways To Save On Your Energy Bill.
If your radiators have just normal valves fitted then you could save by installing Thermostatic controls valve, this way once a room reaches temperature it shut down and as the temperature drops, it opens back up. A central room thermostat will also help adjust the temperature.
By turning it down just a little will save on the gas bills. There are many more ways to save, but these are just a few of the basics. The most important thing that most people seem to forget is to have a regular service because the condensing boiler is set up to save money they need to be checked at least once a year, to keep them tuned. If you don’t service the boiler you will notice your bills going up slowly over time.
Always use a registered Gas SafeCompany to carry out your boiler service.