Pressure rising on an unvented system

[Glen Eley]

Hi all,

The pressure bar in my unvented system is rising. It’s set at 1.5 and rises to 2/2.5. I know it will rise when the water is heating but this now doesn’t drop. I have an Oil boiler and at present only the hot water is on.
I have reduced the pressure by bleeding a radiator.

My question is is it likely to be the expansion vessel or the PRV causing the issue?

The expansion vessel feels pretty full of water and I just isolated the cold water feed to the hot water cylinder, run a hot water tap until the water ceased to come out and the expansion vessel emptied of water. On turning the isolator back on the expansion vessel now feels full of water again.

So any advice on where the fault lays would be appreciated.

Thanks all

 

[Deleted member 120897]

Expansion related issue, so likely the vessel. It’s not a diy fix though, G3 Engineer for unvented, oftec for the oil boiler.

 

[ShaunCorbs]

I’m guessing you mean the heating system as you vented / dropped the pressure by a rad when cold and everything off does it still rise ?