Patent attributes
A gas fired furnace capable of operating with a 16:1 turndown ratio or greater. The furnace includes a plurality of burners (10) grouped into at least (14a) first and second (14b) groups, each group connected to a source of combustible gas through a control valve (30a, 30b, 30c). The control valve (30c) controlling at least one group of burners is of a modulating type having an output proportional to a control signal applied to the valve. The burners fire into associated heat exchange tubes (20a), each tube having an inlet (24) and an outlet. The tube outlets are connected to a collector chamber (44) that includes a baffle plate (60) that divides the collector into two sections, one of the sections communicating with the outlets of the tubes associated with the first group of burners, the other section communicating with the outlets of the heat exchanger tubes associated with the other group of burners.
