The GT-140-NIH is a new breed of tankless for smaller spaces. This model also uses existing 1/2" gas supply lines and inexpensive PVC venting to lower installation costs. The GT-140-NIH 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 systems, and/or domestic & heating applications. ENERGY STAR® qualified 15-year limited Heat Exchanger Warranty, 5-year parts warranty, 1-year labor warranty for Residential applications Copper Heat Primary Exchanger Stainless Steel 316L Secondary Exchanger Complies with Ultra-Low NOx regulations of less than 14 ng/J (<20ppm) Condensing Indoor model Safety features include freeze, overheat, surge protection, and troubleshooting diagnostic codes