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
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: