A furnace control apparatus is described wherein a flow of gas into a burner assembly is directly dependent on an indicia of burner combustion air airflow, such as heat exchanger pressure drop. According to one embodiment of the invention, a first communication fluid line is interposed between a gas...http://www.google.ca/patents/US5860411?utm_source=gb-gplus-sharePatent US5860411 - Modulating gas valve furnace control method
