Vaillant Thermoblock combi boiler - how to up the pressure?

[facelikebambi]

Hi

Vaillant Thermoblock gas combi boiler... it is heating water, but I noticed that the pressure gauge is always at 0 when cold. When radiators are being heated, the needle wobbles around 1 bar. I thought it should always be up there, or a bit higher...

Might explain why the heating doesn't get that hot?

I think I need to top up the heating water, and the little instruction manual talks about turning this little white valve to the left (anti-clockwise) until the pressure raises. (pink arrow in pics)

Vaillant Thermoblock 1

• facelikebambi
• 26 Nov 2008
• 3

Vaillant Thermoblock 2

• facelikebambi
• 26 Nov 2008
• 3

Have I got that right? It seems stuck fast - tried pliers on it and WD40 but it really won't budge. I don't want to break things... any advice welcomed!

Many thanks,
Jason

 

[facelikebambi]

oh... after a bit of fiddling I found that the white knob (red arrow in pic) is a water isolation valve, and is already fully open.

Not sure what to try next...