Technical Service Bulletin

Burner is locked out with fault code F8 on Vitocrossal 200

Applies to: Vitocrossal 200, CM2 Series (models 400 to 620)

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The burner is locked out, and fault code "F8" is displayed on the burner control unit.
Repeated flame loss during phase 6 or 7 on the burner control.



1. Combustion characteristics are not ideal.
2. Condensate on the flame sensing electrode.
3. Boiler does not have its own gas regulator, or the regulator is too far away.



1. Ensure combustion air is not contaminated. Ensure proper gas pressure, correct fuel type, correct gas pipe sizing and correct regulator sizing. Check for dust clogging the burner cylinder.

2. The supplied burner insulation wool needs to be packed around the burner tube and electrodes where they pass through the burner door refractory to prevent the formation of condensate on the flame sensing electrode.

3. Ensure each boiler has its own gas regulator. Each regulator must be installed as close to the boiler as possible.


Viessmann Technical Services


Bulletin ID:


Date issued:

March 22, 2017

Updated on:

November 24, 2017

Revision #:


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