Control for heating apparatus

Claim 1

A heating apparatus comprising a sealed casing holding a combustion chamber, combustion means in the chamber, means for supplying a combustible to the combustion means, heat exchange means associated with the combustion chamber, a first fluid flow circuit including an inlet conduit for air leading to the combustion chamber and an outlet conduit for non-diluted combustion gases leading from the heat exchange means, a second fluid flow circuit including a by-pass branching off directly from the air inlet conduit to the outlet conduit for the non-diluted combustion gases, a fan means forcing the air through the first circuit from the inlet conduit to the combustion chamber and forcing the non-diluted combustion gases through the outlet, and forcing the air through the second circuit by-pass, the fan means being arranged to exhaust the combustion gases from the first circuit and the air from the by-pass together, and means including a bimetallic device for detecting the temperature of the combustion gases coming from the heat exchange means arranged in the first circuit in the outlet conduit for the non-diluted combustion gases and being responsive to the detected temperature for modifying the fluid flow through at least one of the circuits until the volume of the air forced through the first circuit into the combustion chamber corresponds to the volume of air necessary for obtaining an operating efficiency at least close to an optimum efficiency of the heating apparatus under the detected temperature, supplementary air volume passing through the second circuit.