Woodfuel heating systems : installation and management

 

Principles and practical aspects of installation

There are several important issues and principles involved in the correct installation and management of woodfuel heating equipment. It is not necessary to have any practical installation expertise, e.g. plumbing, to appreciate these principles.

Good installation and management practice involves several complementary elements:

• An appropriate choice of burning equipment
• Properly prepared and dried fuel, i.e. a ‘fuel quality’ that is appropriate for the equipment and the heating demand
• Knowledge of, and competence in, operation of the equipment
• Specifying appropriate installation to meet the needs of the system and customer requirements.

Woodfuel water heating system control features

• Coping with the heat
  Heating demand, especially from smaller buildings, does not always match up to the considerable heat output from a boiler when it is operated with maximum efficiency.
   
• Control features
  To maximise combustion efficiency over the range of boiler settings, the length of time the boiler operates with a surrounding cold boiler jacket should be minimised.

Woodfuel heating system controls

• Log-fuelled equipment
  Burning logs is a well-established method of generating heat from wood and three main categories of log-fuelled heating equipment have been developed: direct air heating, indirect air heating and ‘wet’ system heating.
   
• Chip-fuelled equipment
  The system control principles are the same as those for log-fuelled equipment but such systems may be more easily accommodated because combustion control is easier to achieve with this more homogeneous fuel type.
   
• Pellet-fuelled equipment
  Wood pellets are the densest form of woodfuel. Their relatively small size enables the right quantity of fuel to be readily and accurately fed into the boiler.
   
• Woodfuel briquettes
  Woodfuel briquettes are reconstituted fuel, similar to pellets but comparable to log fuel in size. However their size means that they must be burnt on the same appliances and installation systems as logs but having generally slower burning time are more suited to 'idling' conditions.

Dual and alternative fuelling

Many modern log-fired woodfuel boilers incorporate a facility for dual fuelling. This arrangement permits firing into the same internal heat exchanger with an oil or gas burner as an alternative. Built-in water jacket electrical immersion heaters are also an option.

Emissions

Most present-day designs of woodfuel heating equipment operate at high levels of efficiency, so smoke emissions are comparatively low. No equipment works at 100% efficiency so there will always be some emissions.