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.
Before you start
- Ignition, flame, gas pressure, combustion and venting codes are blocked: shut the gas off if you smell gas and refer to a licensed gas technician
- Do not open the combustion chamber or gas train
- Unit has 120 V electronics; caution with covers off
Diagnostic steps
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