Viessmann 100 WB1B 35kW error code fd

[brownmruk]

Hi
In case it helps anyone else, I just wanted to post about an unusual issue I had with error code fd showing on my Viessmann Vitodens 100 WB1B 35kW system boiler. After much head scratching it turned out the problem was that our mains voltage was too high (257V at the time) and the boiler electrics didn't like it. Basically as soon as the voltage hits 254V, our boiler shows the fd fault. If I turn on the tumble dryer (for example) that drops the voltage a bit and the error code clears. It took a while to work out what was wrong because the voltage was only high enough to cause the problem in the middle of the night and the boiler was working fine during the day.
We are the first house in line after the local transformer and late at night when electrical load is low, our voltage kept creeping up. I contacted SP Energy and the engineers made adjustments to transformers further up the line and our voltage was reduced to a more sensible level.
I was prompted to write this as our mains supply was at 260V at 2.00 am this morning and I am waiting on them to come out and have another look (this is the 3rd time since 2014).
Anyway, I post this in the hope that it helps someone else who is struggling to work out what might be causing an fd code.

 

[ianmcd]

It is very unlikely that this is your actual problem, this wouldnt cause an FD code, got a feeling you will keep having the same problem, nothing to do with the incoming voltage being too high

 

[brownmruk]

Hi Ian. Thanks for your interest.
Maybe my post wasn't as clear as it could have been. I wrote that post following two (probably three) instances of high voltage causing the fd error over a 5 year period. On the first occasion in 2014 a Viessmann engineer visited twice and said he could see nothing to cause the error. He did notice that our voltage was a bit high but he was there during the day and didn't think it was causing the problem. When our excessive voltage (reading 255V in the early morning) was lowered by SP Energy network engineers, the problem went away. No fd problems until two years later. Then, after testing the voltage, I called SP Energy right away and after they tapped down the transformer again, the fd code stopped appearing. Now I have the same problem again (except we are getting 260V) and I fully expect the issue to resolve itself when the SP Energy engineers do their stuff. As I said in my post, the boiler works fine all day when there is load on the mains network and we receive about 245V. But when my neighbours go to bed, the voltage climbs. When the voltage is too high (>254V) our boiler throws an fd code. I can temporarily manipulate the voltage lower by increasing the load in our house (by turning on a heavy load like the tumble dryer). That drops the voltage sufficiently for the code to disappear and the boiler kicks back in.
Perhaps you think that is all a coincidence or do you have another explanation for an fd code that only appears in the early hours of the morning?
After I sent that post, I found another post on this forum about a Viessmann fd error and it appears to have been resolved after the mains voltage was tapped down, so perhaps this situation is not as unusual as I imagined.

 

[brownmruk]

Duplicate post deleted

 

[ianmcd]

Hi I see a fair amount of these boilers and have seen the FD code but never been down to excessive voltage, not saying it couldnt happen as the PCBs on these are very erratic to say the least,when you get the FD code does it then show a number or is it just FD ?

 

[brownmruk]

Just fd

 

[ianmcd]

Not sure , as said the pcbs on these can be a bit of a mare