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Rinnai · Wall furnace

99 Flue blocked

Critical severity EX DT

What the control is telling you

The flue is blocked, so exhaust gases cannot be expelled safely.

Applies to: Rinnai EnergySaver direct vent wall furnaces EX08DT, EX11DT, EX17DT, EX22DT

Likely causes

  • Obstruction at or in the flue terminal (snow, ice, debris, nests)

Test and repair steps

  1. Check around the flue terminal and remove any obstruction. The flue must stay clear to expel exhaust gases.
  2. Turn the furnace off and back on with the ON/OFF button to try to clear the code.
  3. If the furnace still does not operate, contact a qualified service agency.
  4. Inspect the flue for blockage or damage at least once a year.

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Source: Rinnai EX08DT/EX11DT and EX17DT/EX22DT Installation and Operation Manuals (200000083, 200000084), Table 9 'Diagnostic Codes', p.35–36. 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.