The AERCO Esteem 399 is a wall-hung boiler with a uniquely designed stainless steel heat exchanger with 95% efficiency. It offers all the benefits of the new generation high efficiency, modulating, condensing boilers along with easy installation, low maintenance and high reliability. The Esteem natural gas boiler can be retrofitted in the field to propane by simply changing a gas orifice. The condensing heat exchanger design is built to withstand thermal shock and eliminates the need for boiler pumping equipment to lower the size, cost, and operating expense of components throughout the entire heating loop. The forced draft, modulating burner operates with 3.6:1 turndown to deliver up to 95% thermal efficiency while simplifying the venting system. Compact in design, the Esteem 399 requires minimal space. It measures only 20 ¾ D x 24 ¾ W x 37 ½ H (inches) and weighs 200 lbs. Simple to install, the boiler can be designed with direct or conventional venting made from PVC, CPVC, Polypropylene or Al29-4C materials to fit any code requirement.