Technical Service Bulletin
Issue: Burner is locked out with fault code F4
Applies to: Vitocrossal 200, CM2 Series (models 400 to 620)
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.
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Reoccurring burner lockouts, and fault code "F4" is displayed on the boiler control.
Flame does not build during the safety time, and no signal is captured by the ionization flame monitor.
Prior to August 2019, Vitocrossal 200 CM2 boiler models 400, 500 and 620 were produced with an older type ionization electrode (without nickel-iron). In some cases, these older type ionization electrodes can fail prematurely.
If the boiler is using the older type ionization electrode and has the symptoms listed above, then replace the ionization electrode with the new nickel-iron (NiFe) ionization electrode, part number 7861491.
As of August 2019, all Vitocrossal 200 CM2 boilers are being produced with the new NiFe ionization electrode.
All replacement (spare parts) ionization electrodes for the Vitocrossal 200 CM2 models 400, 500 and 620 have been the NiFe type since 2018.