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Maximising boiler Efficiency

In addition to making sure that your property is as energy efficient as possible before you install your boiler (see reviewing energy efficiency), there are additional steps you can take to maximise the efficiency of your wood fuelled boiler, which have been covered loosely in points 1-9 of this guide to a successful installation but are worth repeating as maximising the efficiency of your boiler is essential if you are to realise the full financial and environmental benefits of a woodfuelled heating system:

1) Ensure the size of your boiler has been correctly specified. Getting your boiler or stove size right will save you money. Over specifying your boiler will lead to higher fuel costs and carbon emissions. Wood fuel boilers typically work best under a relatively constant load. So, to maximise efficiency, it is worth fitting a wood fuel boiler that provides between 80%-85% of the heat load, click here for more on boiler sizing. The peak load can then be met through accumulator tanks, which store heat in periods of low demand and/or by keeping your old fossil fuel boiler to provide the top up.

2) It is essential to source fuel which meets the specification of your boiler so check the requirements of your boiler before arranging fuel supply, getting the moisture content right is especially important.  A fresh green log of average moisture content (approx 55% MC) has only around half the accessible energy content of an equivalent, well seasoned log (approx 20-25% MC). Energy will be used to evaporate any water in the wood before it will burn, reducing the net energy content released as useful heat.

Ideally logs and wood chips will have a moisture content of less than 25 per cent. Wood pellets need to be drier - at around 8 per cent moisture. Your supplier should give you information about how to achieve this. If your potential supplier has any woodfuel accreditation then they will need to meet set specifications for the scheme, so you can be certain of the moisture content and particle size of the fuel.

3) Ensure your boiler is maintained on a regular basis; see your installer for details on any weekly/monthly and annual checks.