(under the class definition) Apparatus having (1) two distinctly different types of heat generators, (2) a heat generator and a source of heat that is not a generator or (3) a combustion type heat generating means using two different fuels.
SEE OR SEARCH CLASS
260+, for a residual combustion device burning gas or oil and solid fuel.
126, Stoves and Furnaces,
36, for a combined solid fuel and gaseous and liquid fuel domestic type cooking stove; and subclass 369.1 for a steam box for cooking food products including means for utilizing a second heating fluid other than steam, for heating material. 373, Industrial Electric Heating Furnaces,
1+, for a furnace using a combination of electricity and some other heating medium adapted for operation or granular material such as ore, or for handling molten material fusing at a very high temperature.
392, Electric Resistance Heating Devices,
307+, for a residual electrical heating device combined with at least one other heat source of a nonelectrical nature.