Technical Service Bulletin

Issue:  Burner is locked out with fault code F8

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

Vitocrossal 200, CM2

Important Disclaimer

The information in this bulletin is intended exclusively for licensed heating contractors, and is NOT intended for the end user. This material is NOT intended to take the place of the information contained in the manuals shipped with the product.

Use of this information by unqualified personnel may result in property damage, personal injury or death.

End users are asked to contact a qualified contractor for all installation and service work. If you need assistance finding a contractor in your area, contact your Viessmann Sales Representative, or use our Contractor Locator.

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Symptoms:

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.


Causes:

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.


Resolution:

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:     TSB-008

Date issued:   Mar 22, 2017

Updated on:   Nov 24, 2017

Revision #:      02

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