Rinnai Non-SENSEI Code 70
PC board fault. The control board has reported a fault in itself. Rinnai's list is short — confirm the unit's parameters were set correctly, check every harness at the board for loose or damaged connections, then replace the board. The data-transfer step that applies to the SENSEI generations, where settings are copied from the old board with a cable, is not part of the Non-SENSEI procedure.
Call a proThe verdict
Call a licensed plumber
The most expensive single part on the unit after the heat exchanger. Before agreeing to it, it is fair to ask whether the harnesses were checked — that is Rinnai's step 2 and it is free.
Typical cost: $400–$1,100
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. 57), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Note the unit's age. On an older Non-SENSEI heater, a board replacement can approach the cost of a new unit and that comparison is worth making before agreeing.
- Ask the technician to confirm the wiring harnesses at the board were checked first — Rinnai lists that before replacement.
- Book a licensed professional.
Code 70 on other Rinnai series
Other Rinnai series report code 70 under the same fault name, but each manual is transcribed separately and they do not read alike: