E615Input and memory abnormality (MCU)

Tankless water heaters: reading the code, code history and maintenance data (Rinnai, Navien, Noritz and others)

Tankless units show the active code on the remote controller and/or a display on the unit. Many keep a short code history and a maintenance or performance data screen (flow, temperatures) reached through the control; how to reach it is on the tech sheet, often stored with the unit. Many errors clear by themselves when water flow stops, so the history matters. Gas, ignition, flame and venting codes are blocked: read them, then refer.