Gas fired water heater with exhaust gas fan - has temperature controlled damper regulating combustion air flow

摘要

Heater has a heat exchanger (3) above a gas burner (11) in which water is heated by the flue gases. The gases are discharged to atmosphere through a duct (6) which contains an exhaust gas discharge fan (4). Fresh air enters through an annular duct (5) surrounding the discharge duct (6) and flows round the outside of the heat exchanger (3) to the burner (11). A damper (1) in the side of the exhaust duct (6) above the heat exhanger allows part of the intake air to be drawn directly into the exhaust and thus reduce the air supplied to the burner. This damper is moved through linkage (17) by a bimetal strip (9) in the flue gas path. The gas air ratio is thus varied to maintain constant burner efficiency.