For residential. Air/fuel shut-off system offers double protection, Maintenance free, no filter to clean. Flammable vapor detection sensor. Flexible Venting Options. Vertical or horizontal termination. New Quiet Blower. Self-diagnostic System. Environmentally Friendly Burner: Low NOx design for low nitrous oxide emissions. Self-Cleaning: EverKleen patented system fights sediment build-up, Reduces fuel cost, Provides more hot water. Longer Life. Temperature and pressure relief valve is included, Standard 110 volt electrical connection,8 Foot power cord included. Exceeds National Appliance Energy Conservation Act (NAECA) requirements. 19-3/4 In Diameter X 67-3/8 In Height.