New terms – new knowledge – old myths to dispel for the new technology

Tree surgeons woodchip – can this be used in a boiler?

No – most boilers are very strict about the quality of wood chip that can be burnt in a boiler. This covers the size of the chip, the moisture content and the contaminants. This enables the boiler to operate

• reliably (no blockages)
• efficiently (typical burn efficiency 90%)
• predictable set of fumes (some contaminants would burn to produce poisonous gases)

Smoke – will I see smoke?

Most of the time, your neighbours will wonder if you ever use your new boiler. A typical system will ‘fire-up’ twice per day, when it ignites automatically from cold. This results in a short period when smoke will be evident.

Ash – will I have loads of ash to get rid of?

A typical system has automated ash removal, which pushes the ash into a removable box. Because there are no contaminants in our wood chip, the ash is a valuable fertiliser for gardens. The quantity is surprisingly small.

Efficiency – I see efficiency figures of 90% quoted, why do you quote 80%?

We have used a typical ‘boiler efficiency’ figure as an average from 12 months usage. This term should not be confused with ‘burn efficiency’ which calculates how much of the calorific (meaning link - heat release on burning) content is burnt. The remainder goes into the ash and the smoke. Some quoted efficiency figures quote the best efficiency, which is typically when the boiler is being used at its peak load.

Heat meter – what is it, why is it important?

A heat meter measures the amount of heat delivered by a pair of hot water pipes (out-flow and return). To do this there is a flow meter and two thermometers. With these three measurements, it can calculate the heat delivered. When a heat meter is installed on the main pipes leaving the boiler, then the boiler delivered heat can be measured. This is very useful for measuring the efficiency of the boiler, identifying when faults are occurring and providing a means for valuing the fuel delivered.

Europe – why is it that there are so many more wood-chip systems in Europe and have been for many years?

Europe has had legislation and incentives which have driven the market much faster. In particular, this had lead to the establishment of district heating networks which makes the economics of wood chip heating more favourable. Our planning regulations and code for sustainable homes are now helping to drive the UK market.