Viessmann Vitodens 100W hot water running hot and cold

[lgthomas]

Hi,

Hope someone can shed some light on an issue that i am having with my boiler. The hot water is running hot then cold back to hot and cold again etc. I have looked at the display on the boiler while the water is running. When the water is running, on the small screen a tap symbol appears and below that a flame appears with 5 bars, there is also a temp reading. The temp rises to about 80c then the flame symbol goes out but the tap symbol still shows.

Any ideas on what the fault could be? the boiler is just over 3 years old, central heating appears to be fine.

Any suggestions would be appreciated.

Thanks

 

[Doggit]

Could be a faulty thermistor allowing the water temperature to go too high, then the boiler shuts down, so the water gets cold. Call an engineer I'm afraid.

 

[lgthomas]

Thanks for the reply, could anything else cause this problem? I've recently had the heat plate exchanger cleaned, could it be a fault relating to that?

 

[John D v2.0]

Thanks for the reply, could anything else cause this problem? I've recently had the heat plate exchanger cleaned, could it be a fault relating to that?

Probably didn't clip the dhw output temp sensor back properly, as per doggits post. So it can't regulate the output temperature

 

[lgthomas]

Thank you

 

[Dan Robinson]

Did he can the rubber hoses when the heat exchanger was done?