- Heavy duty stainless-steel tubular heat exchanger - Stainless steel secondary heat exchanger - ComfortNet Communications System compatible - Two-stage gas valve provides quiet, economical heating - Durable Silicon Nitride igniter - Quiet two-speed induced draft blower - Uses ComfortNet communicating,two-stage or single-stage thermostats - Self diagnostic control board with constant memory fault code history output to a dual 7-segment display - Color-coded low-voltage terminals with provisions for electronic air cleaner and humidifier - Efficient and quiet variable-speed airflow system gently ramps up or down according to heating or cooling demand - Multiple continuous fan speed options offer quiet air circulation - Cabinet air leakage (QLeak) = <2% - Auto Comfort and enhanced dehumidification modes available