With an industry leading 10 year heat exchanger warranty, The NORITZ NCC199CDV is the state of the art commercial tankless water heater. �It has all the features one would expect from NORITZ, the Global Leader in Tankless Technology, including durable 316L heat exchangers and fully modulating gas valves (98% efficient) �What more, using a quick connect cable, or system controller, you to link from 2 to 24 units for increased flow and redundancy. �You can also common vent up six units. This model also has Wi-Fi capabilities for trouble shooting and system monitoring. �Valve kit IK-200-1-XX-LF, required for installation, sold separately. �Common companion items include rain cap PRC-1, atmospheric conversion kits SVCK-2, quick connects and system controllers. �Non return valves required when common venting (CDVNRVK).