90
Noritz
Abnormal Combustion
Boiler shows error 90 and shuts down during operation.
Advertisements
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Advertisements
Possible Causes
Incorrect gas pressure, Blocked burner or vent, Improper air-fuel ratio, Dirty heat exchanger
How to Fix / Troubleshooting
Critical safety: Abnormal combustion can produce dangerous carbon monoxide. If you suspect venting or combustion issues, stop using the boiler and ventilate the area.
- 1. Check vent terminations: Inspect intake and exhaust for obstructions, damage, or recirculation (exhaust blowing into intake).
- 2. Verify gas supply: Ensure gas shutoff valves are fully open. Do not adjust regulators yourself.
- 3. Clean air filter (if equipped): Some Noritz boilers have an intake air filter. Remove and clean it according to the manual.
- 4. Schedule combustion analysis: A licensed technician must perform a combustion analysis, adjust gas valve settings, and clean the burner and heat exchanger as needed.
Advertisements
Repair Difficulty
Professional Required
5/5
Required Part
Burner Assembly
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements