Combi boiler - bang when hot water opened

[woytaz]

Ok, sorry, but I was bit busy in my life recently and I have forgotten a bit about this thread. So, I finally contacted Viessman, engineer just came and replaced diverter valve. It's just still fresh but so far so good. No banging noise after opening hot water when CH running. We will see if it's gonna stay like this, but surely it was a diverter valve problem. The engineer said that for some reason this valve was closing/openning too quickly where it should do it slowly. So @andrew77 , you need to push them to replace diverter valve, tell them about my case which is similar.

 

[andrew77]

Ok, sorry, but I was bit busy in my life recently and I have forgotten a bit about this thread. So, I finally contacted Viessman, engineer just came and replaced diverter valve. It's just still fresh but so far so good. No banging noise after opening hot water when CH running. We will see if it's gonna stay like this, but surely it was a diverter valve problem. The engineer said that for some reason this valve was closing/openning too quickly where it should do it slowly. So @andrew77 , you need to push them to replace diverter valve, tell them about my case which is similar.

@woytaz thanks for the update. It's funny because the very first Viessmann engineer (I had 2 different engineers from Viessmann checking this) that came actually mentioned that in his report he would mention that the diverter valve motor should be replaced. On the second visit another engineer came and he only replaced the gauge and did nothing to the diverter valve or the diverter valve motor itself. I am guessing that you probably had the whole set replaced.

I will be contacting Viessmann and asking them to do exactly the same to my boiler. I will 100% mention that this is not an isolated case.