Wood-fuelled central heating boiler - has closed air jacket around fire box above which is water coil for heating by indirect exchange

摘要

The boiler has a rectangular casing (1) within which there is a cylindrical combustion chamber (2). This has a grate (3) and an ash pit (4) below it. Three flue outlets (6) lead to smoke pipes (5) which run into a smoke box (12) at the back of the boiler. A heat exchanger (8) with flow and return connections (9) is placed within the casing (1) above the combustion chamber (2). It is not in contact with the combustion chamber. Water circulates through it. The water is heated by the hot air within the casing. This provides effective heat transfer to the heat exchanger whilst preventing the return water chilling the surfaces of the combustion chamber. This prevents formation of soot and tar when wood is being burnt.