Wood Gasification Boilers
A wood gasification boiler is a central heating boiler which produces its useful heat through combustion of wood gas. This “generator” gas is produced by the thermal transformation of wood fuel i.e. the wood fuel is first converted to gas then the resulting charcoal is then also converted to gas.
A wood gasification boiler differs from a standard wood boiler by way of the combustion process. In a standard wood boiler, direct combustion of the wood fuel takes place, whereas in a wood gasification boiler, combustion of wood-gas takes place following thermal conversion of the wood fuel to gas.
Buffer Heat Store - A buffer store (accumulator) will be installed in conjunction with your wood gasification boiler to ensure the efficient operation of your boiler. Buffer stores are important heat storage devices, especially for wood gasification boilers. These boilers can only be operated efficiently when combined with an accumulator since controlled operation at part load is more difficult. This is due to the nature of the fuel (generally wood logs). Once combustion take place, the fuel will continue to burn irrespective of whether the dwellings heat load is met. Consequently the buffer or accumulator cylinder in a domestic biomass heating installation is the primary heat storage/distribution device, which is heated by the boiler to a set temperature and can store the resulting high temperature water for long system standstill periods, until heating or hot water is required. The buffer or accumulator capacity should be calculated in accordance with your manufacturer’s recommendations. A rough guideline for establishing the volume of the buffer is available from EN303-5 and from the REIA training manual and is in the region of 55 to 65 L/kW of the rated boiler size.
Flues - The flue is used for the exhaust of the boiler or stove. It can be installed through a chimney or outside the building. The flue must be installed to current Building Regulations. (Part J – go to www.environ.ie ). Some things to look for would be:
- It is above the eaves line by about 1metre 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.
Constructional Hearth - A constructional hearth should be placed (see Part J of the current Building Regulations – go to www.environ.ie) under a stove to separate the stove from combustible material and to provide protection from the threat of fire. The constructional hearth could be a metal or a non-combustible plate. The appliance should not be placed close to the edge of a hearth or any combustible material.
Air Supply - A stove or boiler must have a secure air supply for safe operation (see Part J of the current Building Regulations – go to www.environ.ie). This can be either in the form of a controlled dedicated air supply directly to the appliance, or in the form of a permanent ventilation opening to the room in which the appliance is located. Best practise is to rely upon dedicated ventilation and not on air infiltration and/or leakage in the room. The size of the opening depends on the size of the appliance. Your installer should be able to size this correctly. In addition, extractor fans may interfere with the operation of the appliance causing smoke to spill out of the appliance into the room so please consult with your installer.
Thermal Mixing Valve (Anti Scald Valve) - Best practice calls for the fitting of a thermal mixing (anti-scald) valve. This applies to all hot water systems and not just solar heated water systems. With the current recommendation to store hot water at 60°C to prevent the growth of legionella bacteria it is becoming more of a consideration to install thermal mixing valves. A thermal mixing valve mixes cold and hot water together to ensure the water temperature is safe for people to use.
Thermostats - are used to control the temperature of an area or space. You should consider what the optimum location of the thermostat is; usually it is the living space where you will spend most of your time. It is very worthwhile to have all main rooms “zoned” and fitted with their own thermostat.
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