2 - Aluminized heat exchanger

3 - Induced venting

4 - Adaptive hot surface silicon nitride igniter

5 - Two-stage gas valve

6 - Variable speed blower motor

7 - Multi-port in-shot burners

8 - Sound insulated blower compartment

9 - Cleanable filter

10 - Self-diagnostic controls

All models convertible to horizontal configurations. Three-way vent option on downflow models for faster and easier installation.