The GT-340X3-NEH is well suited for residential applications. American has combined water heating and treatment in a product designed to revolutionize tankless water heating. Our new condensing gas tankless line features X3® Scale Prevention Technology to last three times longer than other tankless models without X3® Technology. Complies with Ultra-Low NOx regulations. The GT-340X3-NEH utilizes commercial-grade copper alloy for the heat exchanger tubing and are approved to work with an external recirculation pump and cross-over valve. Certified up to 10,100 ft. altitude.