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Rinnai · Tankless water heater

16 Outlet water over-temperature safety shutdown

Critical severity Non-SENSEIRH180 hybridSENSEI RX/CXSENSEI

What the control is telling you

Safety shutdown triggered because the outgoing water temperature went above 203°F (95°C).

Applies to: SENSEI Series; SENSEI RX/CX Series; Non-SENSEI Series

Likely causes

  • Restricted air flow at the vent terminal
  • Fan not operating properly
  • Check valve behind fan motor stuck and restricting air flow
  • Debris in combustion chamber or exhaust piping
  • Blocked heat exchanger
  • Unit set to wrong gas type (e.g. Parameter 10 incorrect)
  • Faulty gas valve or fan motor assembly

Test and repair steps

  1. Look for anything restricting air flow around the vent terminal.
  2. Confirm the fan operates correctly.
  3. Make sure the check valve behind the fan motor is not stuck and blocking air flow.
  4. Check the combustion chamber and exhaust piping for foreign material.
  5. Check the heat exchanger for blockage.
  6. Confirm the unit is configured for the gas type on its rating plate.
  7. SENSEI / SENSEI RX/CX Check Parameter 10 (A = Natural Gas, B = Propane). On RX/CX models, Parameter 10 can only be changed within 20 minutes of a power reset.
  8. If the fault persists, replace the gas valve assembly, then the fan motor assembly if needed.

Settings for these units

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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.27. Summarized in our own words; check the original manual for your model.

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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.