Viessmann Vitodens 100W running hot and cold

[bojay]

Hi everyone thanks for your replies just an update. Threatened installer with solicitors and all of a sudden he said Viessman would come out and look without charge.

They came today and have ordered flow sensor and H/W sensor.

We will wait for them to be fitted and update you then.

Thanks again

 

[Agile]

I would have expected him to carry both of those!

Tony

 

[bojay]

Hi everyone

just an update sorry should have done it earlier. Man from Viessman changed two sensors. The farthest taps from the boiler work perfectley adequately now even on low flow still produce hot water. The kitchen one on low flow will still run hot then cold - if you turn it up to half it will stay warm continually. The guy told me this is because it is an old plastic 90's tap and the flow sensor is not picking it up on low flow so need to get a new tap!

 

[tomkut]

Dear (DIYnotters?)
Maybe someone knows if the flow sensor can be replaced with one from vaillant or Glow worm Ultracom for their lower switching flow, 1.5l/min and 1l/min, respectively?

 

[Agile]

Ask Viessmann as using another product would invalidate their warrantee.

But the flow sensor is not the problem. Its the minimum power out of the boiler would make it turn on/off.

Tony

 

[tomkut]

Agile, note that they would not necessarily know about this if I swapped back before the next boiler service.

As far as I can see the boiler goes on/off anyway, especially when in comfort mode. Are you suggesting that the other two brands boilers can modulate down to <half (glow worm) of what viessmann can? I don't think so.