The nc1991 199 900 btu propane tankless water heater has a maximum of 9.8 Gpm with optional multi-system up to 6 units. The direct vent concentric system allows stainless steel double-wall venting to be installed. This commercial water heater heats water up to 185 degrees and meets federal and state air quality standards which are below 20 ppm. Features: 9.8 Gpm tankless water heater provides enough hot water to run from 2 to 3 hot water appliances at 1 time tankless gas water heater costs less to operate than electric models energy star qualified tankless water heater is highly efficient and uses up to 40% less energy than storage water heater models 5 year warranty on the heat exchanger 5 parts plus all noritz models feature a 1-year in-home warranty specifications: width: 13-13 16 height: 24-3 16 depth: 10-3 16 product weight: 55 fuel type: gas gas type: liquid propane gas connection: 3 4 water connection: 3 4 water pressure min : 15 psi water pressure max : 150 psi temperature min : 100 degrees f temperature max : 185 degrees f voltage: 120v frequency: 60 amperage: 1.341