HVACopedia

Rinnai · Tankless water heater

13 Combustion fault

Critical severity RH180 hybrid

What the control is telling you

On the RH180 hybrid, the unit detects a combustion problem. Look at venting, combustion air, altitude/gas settings, the fan and the burner.

Applies to: RH180 hybrid tank-tankless (non-SENSEI) only

Likely causes

  • Vent not 4 in. B-Vent or installed incorrectly
  • Not enough combustion air in the room
  • Altitude DIP switches set wrong
  • Inlet or forced low/high manifold gas pressures out of range
  • Restricted fan wheel or housing
  • Clogged burner orifices, debris in the burner, or fouled heat exchanger fins

Test and repair steps

  1. Make sure the vent is 4 in. B-Vent installed per the manufacturer's requirements.
  2. Inspect the whole vent inside and out clearances, approved materials, sections fully seated, and joints sealed so they cannot pull apart.
  3. Check that the room has enough combustion air for all gas appliances in it. If the unit runs with a door left open, recalculate combustion air for the space.
  4. Check the altitude DIP switches (SW2/SW3 per the table on p.22 or the Tech Data Sheet).
  5. Warning: Only gas-qualified technicians should do the gas pressure steps.
  6. Inlet gas at full fire NG 4–10.5 in. W.C., LP 8–13.5 in. W.C. Forced low: NG 1.10 / LP 1.23 in. W.C. Forced high: NG 2.8 / LP 3.0 in. W.C.
  7. Caution: Turn off power, remove the fan motor and check the wheel and housing for restrictions. Refit, restore power and see if the code returns.
  8. Warning: Turn off electrical, gas and water. Then check the manifold orifices for blockage, clear debris from the burner and air chambers, and check heat exchanger fins for build-up.

Settings for these units

Models that show this code

1 model in RH180 hybrid

RH180

Other codes on the same units

  • 03 Power interrupted during bath fill
  • 05 Bypass flow control device fault
  • 07 Circulation flow rate below 2.1 GPM
  • 10 Air supply or exhaust blocked / condensate trap full
  • 11 No ignition
  • 12 Flame failure
  • 14 Thermal fuse or overheat sensor tripped
  • 16 Outlet water over-temperature safety shutdown

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.22. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.