Viessman Vitodens 200

The heat exchanger rating plate doesn't give the correct info to identify the unit. If you have an E8 you should start by checking the gas supply, gas pressure static and dynamic, checked at the unit, , not manifold pressure you need supply pressure and you need to know the max drop in gas pressure. record 4 values Static, ignition, high fire, and shutdown. check the fuel type is selected both in the programming, and on the gas valve(if applicable to your unit) correctly. then check the gaps on the igniter and flame sensor per the manual, or replace them. if your unit is shutting down with no fault code there are 2 things I know of that can do this, on the regular and large water tube unit, the flow switch safety will shut the boiler down if it has low flow, the largest commercial wall mount units make use of 2 very expensive flow sensors, they are very accurate and typically don't fail, but can be damaged (though unlikely) on the larger commercial units you will also see gas pressure safeties attached to the gas valves, these are normally OPEN safeties that will shut off the burner with a hidden error code if they are closed. One thing that can happen is condensation dripping on these will close the contacts and lock the boiler out. these use an external blocking demand signal instead of a standard safety which is why they do not trigger a fault.

If you actually have an EB error the issues are going to be similar, and with either one might as well do a full service on the boilers burner etc