The boilers for metre lengths
Manually Fired Boilers
The principal rule is that manually fired boilers for fuelwood only have an acceptable combustion at the boiler rated output (at full load).
At individual plants with oxygen control, the load can, however, be reduced to approx. 50% of the nominal output without thereby influencing neither the efficiency nor emissions to any appreciable extent.
By oxygen control, a lambda probe measures the oxygen content in the flue gas, and the automatic boiler control varies the combustion air inlet.
The same system is used in cars. In order for the boiler not to need feeding at intervals of 2-4 hours a day, during the coldest periods of the year, the fuelwood boiler nominal output is selected so as to be up to 2-3 times the output demand of the dwelling.
This means that the boiler efficiency figures shown in Figure 15 and 16 should be multiplied by 2 or 3 in the case of manually fired boilers.
Boilers designed for fuelwood should always be equipped with storage tank.
This ensures both the greatest comfort for the user and the least financial and environmental strain. In case of no storage tank, an increased corrosion of the boiler is often seen due to variations in water and flue gas temperatures, and in addition to that, the manufacturerwarranty may also lapse.
The size of the storage tank can be determined on the basis of Figure 18.