Combined fan and ignition control with selected condition sensing apparatus

摘要

An electric control is shown adapted for use with gas furnaces which controls fan motors, ignition controls and a gas valve based on inputs from a room thermostat, limit switches, a flame probe, a flame roll-out probe, and a condensate sensor. A roll-out detection circuit utilizing flame rectification includes a multidirectional roll-out probe 16 coupled to a microcontroller (U2) through an inverter (U3) to provide both fault both protection and fault identification. A condensate sensor (20) in the form of a conductive condensate sensor member is also coupled to the microcontroller (U2) through an inverter (U3) to detect the presence of condensate build-up.