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Rinnai · Tankless water heater

30 Flammable vapor sensor activated or faulty

Critical severity RH180 hybrid

What the control is telling you

The flammable vapor sensor has tripped or failed; flammable vapors may be present near the water heater.

Applies to: RH180 (Hybrid Tank-Tankless Non-SENSEI Series)

Likely causes

  • Flammable vapors present in the installation space
  • Loose, damaged or broken sensor wiring or connectors
  • Flammable vapor sensor mis-mounted or damaged
  • Failed flammable vapor sensor
  • Failed PC board

Test and repair steps

  1. Warning: Vacate the room until safety personnel confirm the area is safe and all flammable vapors are removed.
  2. Warning: Only technicians qualified to service gas water heaters should continue.
  3. Disconnect power to the water heater.
  4. Remove the front panel and inspect the flammable vapor sensor and its harness, from sensor to PC board, for loose, damaged or broken wires/connectors.
  5. Confirm the sensor is mounted correctly and undamaged.
  6. Only when certain no vapors are present, restore power and gas, open a tap and fire the unit.
  7. Check D1 connector Red–Black pins (D) 1–6 = 1.9–2.1 VDC; White–Yellow pins (D) 4–3 = 25.5–39.5 mVDC.
  8. If code 30 returns with no vapors present, replace the flammable vapor sensor; if still unresolved, replace the PC board.

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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.35. 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.