Noritz NRC1111-DVNG Residential Condensing Tankless Water Heater, Natural Gas Condensing technology - The most advanced Noritz unit, over 93 percent efficiency level! Combi-system set-up - Open loop system functionality for both potable water heating and space heating combination system Safety lock out - Default max. 120 degrees F (refer to owner's manual for higher temp) Dual flame burner - Noritz exclusive! Minimizes temperature fluctuations Fully modulating - Automatically adjusts burner level accordingly