The NCC1991 condensing tankless water heater from Noritz America delivers a thermal efficiency of 95%, using natural gas, with an input range of 16,000 to 199,900 Btu. The company says this enables the unit to meet the hot water needs of larger residential applications as well as a wide variety of commercial projects. The NCC1991 is the low NOx version of Noritz’s NCC199 condensing tankless unit.

Using a special Quick Connect cable, two NCC1991-DV units can be coupled to provide an input of nearly 400,000 Btu, with a turndown ratio of more than 36 to 1. Up to 24 units can be combined into a single system, making the NCC1991 ideal for applications where hot water demand can vary substantially over the course of a day or throughout the year.

To obtain its 95% efficiency level (97 percent with propane), the NCC1991 uses a secondary heat exchanger, made entirely of stainless steel, to capture residual heat from the unit’s exhaust to preheat incoming water before it enters the main copper heat exchanger. This heat recovery process lowers the temperature of the flue gases, allowing exhaust vent runs with less expensive PVC piping rather than the stainless steel venting required by conventional tankless water heaters.