Rinnai Non-SENSEI Code FF
Maintenance performed marker. Not a fault. It is a placeholder a service provider enters into the diagnostic code history to record that maintenance or service was carried out, by pressing UP, DOWN and ON/OFF together. If you are reading the code history and find FF, it marks a service visit.
DIY fixThe verdict
No parts needed — reset or re-check a setting
Nothing is wrong and nothing needs doing. If FF is on the display rather than in the history, clear it from the controller.
Typical cost: $0–$0
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the Non-SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 64), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Nothing to fix. If you are reading the code history, FF marks a point where someone recorded a service visit.
Code FF on other Rinnai series
Other Rinnai series report code FF under the same fault name, but each manual is transcribed separately and they do not read alike: