Viessmann Control Unit problems

[AndyMH]

Hi,

Are there any Viessmann experts out there who could give us some idea why I cannot change out the weather compensated control unit for the standard one?

We have a Vitodens 200 WB2B with weather compensation which we have had for approx 7 years, its been nothing but trouble - started with the screws holding the plate heat exchanger on loosening themselves and flooding kitchen, flame sensor needs cleaning at least every 6 months or you get F4 errors after cold nights, air release valve leaked, plate heat exchange blocking every couple of years (finally solved that one after realising installer should have put filter on system and adding one), its been the worst purchase we've every made.

However the real pain is the weather compensation, it just doesn't work, regardless of how much you fiddle with the settings. On mild days its OK, on mild sunny days its too hot, on mild windy days its too cold, then the weather turns cold and the house is freezing, fiddle with the settings and its OK until the weather warms up and then house is roasting etc etc. I guess in a new build it would be fine, just not an old Victorian one.

Replacing it isn't an option at the moment and since it was time for its 6 monthly cleaning of the flame sensor I decided enough was enough and dug out the original standard programming unit that the installer removed when he fitted the boiler. I installed a room thermostat, removed the weather compensation programmer from the front panel and put the standard one on.

When the boiler starts up it faults with a b1 error, internal communication fault. The programmer appears to be working, I can set heating programs, go through coding 1 and 2 to change things etc but cannot get rid of the fault. If I pop the programmer off and put the weather compensation one back everything is fine.

Does this mean the boiler is somehow coded to only work in weather compensated mode or have a missed a setting somewhere that needs changing as well?

Any advice would be much appreciated!

Andy

 

[Phill Peck]

I think u may need to change some of the onboard coding to tell the boiler what controller it has. Ring Viessmann technical on 01952 675000 and they will talk u through.
(I can't be arsed to look up the codes there are hundreds)

 

[AndyMH]

Thanks, will give them a try, hadn't considered it as they have been spectacularly unhelpful in the past!

 

[Phill Peck]

I've always found them very helpful. Possibly because I'm a gas engineer though.
They may not be to keen on giving details of all the coding.(there are different levels that require pass codes) but I think which controller is fitted will be in the 1st level.

I've not known anyone have as many problems as u have had with your boiler. Especially a 200 model.
Having said that. The air release valve and blocked plate ate due to dirty water. This is more of an installation defect that the boilers fault.

 

[AndyMH]

In defence of the boiler I don't think the installer really knew what he was doing, he spent 3 days installing it most of the first 2 were flushing the system and most of the 3rd was on the phone to Viessmann!
The F4 fault is the real pain, as you tend to get them on cold frosty mornings like today when the heating should have been on low all night. I've taken to rubbing the probe clean with an old toothbrush or very fine wet&dry every 6 months as a preventative.

 

[Phill Peck]

Do u have this boiler serviced? By someone who knows what they are doing?
Electrodes should last years on these boilers. (Being cleaned on service)
Sounds as though combustion isn't very clean for electrode to need cleaning so regularly.
I'm assuming u know u shouldn't be taking the front off and removing parts especially those that are part of combustion/ seal the combustion chamber.

 

[AndyMH]

We have had yes, each time the exhaust analysis has been in range so nothing adjusted, just condensate cleaning out, spark electrode gap checking and flame probe cleaning. Last couple of years haven't bothered as basically we've had just as many problems without service as with.

The electrode has a red-ish coating that is very easily removed, not corrosion-like more of a deposit which I have assumed is from combustion but since its never apparently needed adjusting I also assumed thats just the way it goes. Will probably get it done again before next winter.

Yes I am aware I shouldn't be doing it but if I had paid someone to do everything that has gone wrong it would have been an absolute fortune. I always replace the gasket on flame probe each time. Would never open the main chamber, if I recall correctly that would need the gas supply disconnecting, I'm a competent mechanical & electronic engineer but that's a step too far without specific gas training.