Fully modulating, Ultra Low NOx, gas fired, tankless water heater specifically designed for residential and commercial applications. Supplies hot water to domestic hot water systems (directly or indirectly) which can be used with storage tanks, recirculation systems, hydronic heating systems, radiant floor heating systems, and/or combined domestic and heating applications. 15-year limited Heat Exchanger Warranty, 5-year parts warranty, 1-year labor warranty for Residential applications 5-year limited Heat Exchanger Warranty, 5-year parts warranty, 1-year labor warranty for Commercial applications Commercial Grade Copper Heat Exchanger Ultra Low NOx emissions of less than 14 ng/J (<20ppm) Easy-Link up to four units without a Multi-Unit Controller Multi-Link up to 20 units with a Multi-Unit Controller Convertible from Natural Gas to Liquid Propane Non-Condensing Outdoor model Includes a remote control Includes internal freeze protection and multiple safety features