Specifications
to ensure the water temperature is safe for people to use. This is not exclusive to hot water systems heated by
wood, it is important for all hot water systems.
Thermostats and Timers
The control of the boiler on/o times and the temperature in each of the rooms is very important. In order
to read room or zone temperatures and to allow the homeowner to set them, a thermostat is required. A
dwelling will usually have one “master” thermostat per zone. A master thermostat is a thermostat which can
directly call on the boiler for more heat. A “slave” thermostat therefore is a thermostat which does not call on
the boiler, but can still adjust the temperature in the room if the boiler is running. As well as temperature, it
is important that the on and o function of the boiler is timed as well. Some thermostats now are digital and
have built-in timers also.
Flues
A ue is the exit point for the exhaust of a boiler. It can be installed through a chimney or outside of the
building. The ue must be installed to current building regulations. Some general things to look for include:
Is it above the eaves line by about 1 meter or 600mm if coming out near the roof apex?
It is twin walled and insulated
It has a cowl or hood on top to help prevent down draught
It should be separated from any combustible material
The top of the ue is positioned away from any windows or roof lights that might let ue gases back
into the building
The ue outlet is positioned away from walls and other surfaces that might be stained by the ue gases
Size of Wood Fuel Store
In general, and within reason, the larger the storage the better, this means less frequent fuel deliveries are
required and prices tend to be more favourable.
Bulk - for a typical house a minimum four 4 tonnes storage capacity is recommended for chips (18–20m
3
)
and pellets (7– 8 m
3
). This allows advantage to be taken of typical minimum delivery quantities (for example
three tonnes in the case of pellets) at the most advantageous cost. Minimum delivery amounts of chips will
vary from supplier to supplier.
Bagged - mainly applies to pellets. Use of bagged pellets normally indicates that demand is low, for example
very low energy or passive house or that they are used for a secondary heating system (room heating
only stove). There are no particular guidelines on stored quantities required but this may be inuenced by
available covered space, quantity discounts, whether they are delivered or self collected, predicted annual
demand, frequency of delivery required and distance to preferred supplier. It would normally be sensible to
have storage available for 10–20 15 kg bags to satisfy most of the above variables.
Briquettes and Logs
Again, larger purchases will prove more cost eective where the fuels are delivered by the supplier. However,
where these fuels are readily available in the local area, for example from the local co-op, and collected by the
end user it may be possible to maintain a smaller stock. In the case of wood logs where you have your own
supply the storage should be dictated by the quantities estimated for annual use, i.e. store sized for annual
consumption and rotated to allow drying.
Suppliers and installers of equipment should also be able to advise you on sensible fuel storage requirements
based on knowledge and past experience.