- Heavy duty Million Air stainless-steel, tubular heat exchanger - Stainless-steel secondary heat exchanger - ComfortNet Communications System compatible - Two-stage gas valve operates with ComfortNet communicating two-stage or single-stage thermostats - Efficient and quiet variable-speed airflow system gently ramps up or down according to heating or cooling demand - Durable SureStart 110-volt Silicon Nitride Igniter - Color-coded low-voltage terminals with provisions for electronic air cleaners and humidifiers - Self-diagnostic control board with constant memory fault code history output to a dual 7-segment display - Multiple continuous fan speed options offer quiet air circulation - Auto-comfort and enhanced dehumidification modes available - Quiet variable-speed induced draft blower - Cabinet air leakage (QLeak) = 2% - Fully insulated heavy-gauge steel cabinet with durable baked-enamel finish