At up to 94 percent AFUE, this Energy Star-rated boiler uses a stainless steel heat exchanger and Sage 2.1 Control System with factory presets to speed installation. Touchscreen diagnostic display and free five-year parts and limited-labor warranty offer additional benefit. The K2 is available in five sizes ranging 80-180 MBtuh and offers features such as 5:1 turndown and a cold burner door that’s safe to touch, even while firing. The boiler’s simplified design includes a hinged inner door that isolates electronics and controls from combustion and waterside components. A pre-installed, high capacity boiler loop circulator is included, as is an innovative split-voltage junction box, enabling simple, error-free wiring connections. Venting the K2 is simple, regardless whether one-pipe, two-pipe, horizontal, or vertical configurations are needed.