- Heavy duty Million Air stainless-steel, tubular heat exchanger - Stainless-steel secondary heat exchanger - Two stage gas valve with convertible technology that allows installer to activate two-stage operation with the flip of a dipswitch - Self adjusting feature automatically adjusts to high or low stage operation based on outside temperature without the need for an outdoor temperature sensor - Durable SureStart 110-volt Silicon Nitride Igniter - Color-coded low-voltage terminals with provisions for electronic air cleaners and humidifiers - Control board stores last diagnostic codes in memory and outputs the fault history to a flashing red LED - Low continuous fan speed options offer quiet air circulation - Fully insulated heavy-gauge steel cabinet with durable baked-enamel finish