The 59TP6B Multipoise Variable-Speed Condensing Gas Furnace features the two-stage Performancet System. The Comfort Heat® technology two-stage gas valve is at the heart of the comfort provided by this furnace, along with the variable-speed ECM blower motor, and two-speed inducer motor. With an Annual Fuel Utilization Efficiency (AFUE) up to 96.5%, the Performance™ Series two-stage gas furnace provides exceptional savings when compared to standard gas furnaces. This Performance Gas Furnace also features 4-way multipoise installation flexibility, and is available in eight model sizes. The 59TP6B can be vented for direct vent/two-pipe, ventilated combustion air, or single-pipe applications. Low NOx units are designed for California installations and meet 40 ng/J NOx emissions. Can be installed in air quality management districts with a 40 ng/J NOx emissions requirement. All sizes are design certified in Canada. This furnace is not designed for use in recreation vehicles, manufactured (mobile) homes or outdoors.