Viessmann vitodens 50 hot water issue

[Andyneouk]

Hi. I have a viesmanm vitodens 50 but I've noticed it's behavior change recently I think. When running a bath for example, the boiler will fire up and start providing hot water as expected. The temp on the boiler display climbs steadily to about 85 degrees with the burner indicator showing 5 lines (9 being full if that makes sense) . When it hits 85 degrees it cuts back to 1 line, I.e low for a few seconds, the temp drops to about 75 then it fires back to about 5 lines. This repeats. Screenshot below of what I see and mean by 5 lines on the burner.

Is this normal behaviour or should it regulate more i.e sit at 3 or 4 lines.

My nest controls the water temp setting, it's set to 55 so should the boiler even be hitting 85? I suspect I have an issue with the boiler

Thanks in advance
Andy

 

[ShaunCorbs]

It shouldn’t be hitting that high up something is starting to clog / get effected maybe by dirty heating water

 

[Andyneouk]

It shouldn’t be hitting that high up something is starting to clog / get effected maybe by dirty heating water

Hi thanks for the reply. The central heating is working fine. It is likely something that can be cleaned or would I need to get viessmann in?

 

[ShaunCorbs]

A gas safe engineer can do the works but they need to know about Viessmann as there are a few common items

And heating won’t show the issue as it’s not full demand