The ProLine® XE PowerFlex® Ultra-Low NOx power direct vent water heaters utilize an innovative burner system, a combination of radiant heat and excess air to comply with Utah, South Coast Air Quality Management District and other California Air Quality Management Districts with similar requirements of less than 10 ng/J for ultra-low NOx emissions. The 0.70 Energy Factor qualifies these models for ENERGY STAR®. 6-year limited Tank warranty, 6-year parts warranty for Residential applications Newly designed dip tube optimizes inlet water pressure to minimize cold water regions within the tank. The self-cleaning action also reduces sediment accumulation on the bottom of the tank. Hot-surface ignitor is more robust and reliable than standing pilot, and reduces energy consumption Built-in heat traps on the water inlet and outlet reduce the amount of heat lost through piping 2-inch, thick, “Environmentally-Friendly” foam insulation reduces theamount of heat loss and contributes to overall energy efficiency Power Direct Vent Design Combined horizontal and vertical vent runs up to 180 equivalent feet with 4” diameter venting (ABS, PVC, CPVC and polypropylene) Sealed combustion system uses outside air, eliminating problems caused by insufficient indoor ventilation Ultra-Low NOx – Enhanced Ultra-low NOx burner complies with SCAQMD Rule 1146.2 and other Air Quality Management Districts with similar requirements for NOx emissions of less than 14 ng/j State-of-the-art electronic gas control provides more precise temperature control LED control light displays operation status and diagnostics information Factory-installed T&P and a durable, tamper-resistant brass drain valve are positioned for service accessibility