Furnace control apparatus

摘要: An electric control for gas furnaces which controls a two speed main blower fan and an induction draft based on inputs from room thermostat, high limit ignition including valve. The has circuit board having power supply providing 24 volts DC current source to drive relays 5 volt microprocessor. AC input signals are coupled the ports of microprocessor through limiting resistors ground pull down resistors. is also connected IRQ port output relay driver in turn relays. Several breakaway tabs provide optional features such as eliminating normally provided delay timing function. Test pads so that can be tested during manufacture. feature shown comprising LED used indicate status system. Another incorporates zener diode resistor each increase thresholds. This use with stealing electronic thermostats. calibrates itself continuing periodic basis read synchronously at peak their wave switches asynchronously real time clock