Greenstar 32CDi pressure going too high

[Gorners]

Hi all,

I recently moved into a new house with the above system, over that time I noticed the pressure dropping such that I've had to top it up every 2-3 weeks. I found a couple of radiator valves weeping, so nipped them up, which did slow it down but not stopped it. This has been annoying me so have done a bit of digging and I think I've found the cause of the drops.

If I repressure the system when completely cold (display showing ~45 deg) to just 1 bar (as opposed to the recommended 1.2-1.3 bar), once the heating is on, the pressure goes up to well beyond 3 bar, well into the red (gets to 3 bar around 70 deg). This is causing the PRV to activate hence the pressure dropping, the pressure has dropped. I think it has to be down to below 0.5 bar when cold for it to stop hitting the red.

Can someone tell me what could cause this please?

 

[muggles]

Your expansion vessel is either flat or broken

 

[ianmcd]

Yep as Muggles says your expansion vessel either needs re-charged, read the FAQS it will tell you how to do it but follow ALL the steps you can not just pump air into it, it may be burst in which case it will need replacing or an external one fitted, most likely just needs re-charged.

 

[Gorners]

Thanks both. Is the expansion vessel easy to access on this boiler? And can I use the drain off which is underneath the boiler to reduce the pressure?

 

[muggles]

Thanks both. Is the expansion vessel easy to access on this boiler? And can I use the drain off which is underneath the boiler to reduce the pressure?

It is easy to access, it's also inside the sealed chamber of the boiler and as such should only be accessed by an RGI. The pressure should reduce when the temperature goes down again

 

[Gorners]

Perfect thanks for the advice, will call out a heat engineer.