Central heating boiler unit - has return water preheater heated by flue gas drawn from and returned to flue chest connected to flue duct by fan

摘要

The arrangement is intended for increasing the efficiency of a central heating boiler having a fan (10) which draws combustion gases (via 7) from the flue chest (4) and through a second heat exchanger (8) to further reduce their temp. and passes them to a flue duct (5). The chest is, in addition, directly connected to the duct (5) via a down-draught diverter (6) in the normal way. The heat exchanger (8) may be vertically arranged, e.g. by the side of the boiler, and have its upper end connected (7) to the chest and its lower end (9) to the fan, whilst its water space has its lower end connected to the heating circuit return and its upper end to the water space of the boiler.