Boiler for central heating - has heat exchanger in flue duct to preheat return water before entering boiler

摘要

The heat exchanger is for recovering additional heat from the combustion gas of a central heating boiler. It is arranged in the water return line upstream of its connection to the boiler. The combustion gas from the boiler passes through a water container on its way to the flue, the flue duct being provided with fins in the container. It has a water circulation pump upstream of the exchanger and with shut-off valves either side, and a valve downstream of the exchanger. Thermometers for the water and the gas temperature are provided. The gas is cooled to a minimum temperature of 100 deg. centigrade to prevent condensation.