The Noritz SCU-401-12M system controller provides a central communication hub for up to 12 tankless water heaters. The SCU-401-12M provides fully modulating operation among all units and rotates the operation of the units in the system for even wear. Only one remote controller is required to operate the units within the system. A built-in pump control allows recirculation pumps to be connected and controlled with timer and aquastat functions. The SCU-401-12M also features an auxiliary backup for continued system operation during power failure conditions.