Baxi Baxi Heating Boiler Error Code BX013

Baxi Home Boiler Major Flue

Model: Baxi Heating Boiler | Code: BX013

Applicable Systems

Baxi Heating Boiler

Symptoms

The flue gas analysis sensor has detected an abnormal CO2 or CO reading. The boiler enters a safety lockout and displays a flue gas fault.

Step 1: Inspect the flue terminal externally for blockage
Clear any debris, nests, or ice before restarting the boiler
Step 2: Check the combustion air intake path for restrictions
Ensure ventilation openings are clear and unobstructed
Step 3: Use a flue gas analyzer to measure CO2 and CO at the flue test port
CO2 should be 8-9% for natural gas; CO should be below 100ppm
Step 4: If readings are out of specification, clean the heat exchanger and adjust the gas valve
Use a manometer to set the correct gas/air ratio per the commissioning table

Reset: After cleaning and adjustment, verify the flue gas readings are within specification, then press the boiler reset button.

Flue gas analyzer: Electronic, CO2 and CO measurement (Calibrate before use)
Heat exchanger cleaning kit: Brush set and solvent (Match to boiler model)
Gas valve: Modulating type, OEM-specific (Adjust only with a combustion analyzer)

Q: What are safe flue gas readings?
For natural gas: CO2 8-9.5%, CO <100ppm, O2 5-7%. For propane: CO2 10-11.5%, CO <100ppm.
Q: How often should the heat exchanger be cleaned?
Annually for residential boilers. Condensing boilers need the condensate trap cleaned at the same time.
Q: What causes high CO?
Incomplete combustion from restricted air supply, dirty burner, or incorrect gas/air ratio. High CO is dangerous and requires immediate attention.