Apparatus and method for controlling a variable fuel fired appliance

An apparatus is provided for controlling a fuel fired heating appliance, the apparatus comprising a first processor for controlling the ignition operation of the furnace and a second processor for controlling the operation of a variable speed blower motor, wherein the first processor sends communication signals to the second processor requesting a desired speed of the blower motor to provide air flow for combustion. The second processor responsively sends a signal to the first processor indicating the receipt of the requested speed for the blower motor. The apparatus further comprises at least one pressure switch, where the first processor senses an opening of the pressure switch and responds by successively sending incrementally higher speed request signals to the second processor until the first processor detects the closing of the at least one pressure switch.