Don't Get Left Out In The Cold  The Plus 90i (model 355MAV) keeps your home warm and comfortable with up to 96.6% AFUE (Annual Fuel Utilization Efficiency). That's over30% more efficient than typical older furnaces.  1. Primary Three-Pass Heat Exchanger Incorporates an S-shape design for efficient heat transfer. This component is backed by a lifetime limited warranty. 2. Secondary Condensing Heat Exchanger Extends heat transfer for higher efficiency. It is protected by our patented Everlastic™ coating for long-lasting durability. This component is backed by our lifetime limited warranty. 3. Variable-Speed Blower Features a direct-drive motor that operates with precision to deliver quiet, dependable heating. 4. Direct Vent System Eliminates drafts and allows quiet operation by using outdoor air for combustion. 5. Variable-Speed Inducer Motor Quietly draws air from outside and runs at the exact speed needed for the highest efficiency.