The GT-340-NEH offers high efficiency Ultra-Low NOx condensing technology allowing for the use of 3" PVC venting and has 0" clearance to combustibles. Utilizing copper alloy for the heat exchanger tubing. Remote control included as a standard feature. Indoor models are certified up to 10,100 ft. altitude. ENERGY STAR® qualified 15-year limited Heat Exchanger Warranty, 5-year parts warranty, 1-year labor warranty for Residential applications Copper Primary Heat Exchanger Stainless Steel 316L Secondary Heat Exchanger Complies with Ultra-Low NOx regulations of less than 14 ng/J (<20ppm) Condensing Outdoor model Safety features include freeze, overheat, surge protection, and troubleshooting diagnostic codes