Viessmann Vitodens 100 pressure problem

Current problem with vitodens 100 is: On attempted start-up in morning some days it fails to fire;
I find water pressure @ 0.5 bar. When pressure increased to 1.2 (which is pre-set cut-off pressure) it works okay but I note that pressure can swing up to approx. 3.0 bar before settling down to run okay. This has occured a few times over past month or so. On these occasions the weather temperature was in the minus zero centigrade region.
I have had various other problems with this boiler since it was commissioned Nov. 2006 into an existing oil fired, copper plumbed/steel radiator system which had been thoroughly flushed and fernoxed.
Any thoughts?
Kieran

Get someone to check that the expansion vessel is OK. It may have gone flat as in tyre, or the diaphragm may have failed, or the precharge pressure may be too high.

KD01 said:

I have had various other problems with this boiler since it was commissioned Nov. 2006 into an existing oil fired, copper plumbed/steel radiator system which had been thoroughly flushed and fernoxed.
Any thoughts?

Kieran

Click to expand...

Do you mean it replaced an oil fired boiler?

Or is there an oil boiler STILL connected?

Tony