Problem Diagnosis Help...

Hi,

I've got some pressure problems with my Potterton Puma 80e boiler... when heating's turned on, the pressure rises way too high - up to 3 bar and beyond and when you turn it off, it falls way too low to below 0.5 bar sometimes and I need to fill it daily just now which is obviously not good. I've been reading the FAQ and also similar posts but still unsure as to what problem could be.

Boiler problems started when I bled air from a radiator because of cold spot in top half which fixed this problem. My girlfriend unfortunately left the filling loop open most of the day before leaving the house in the morning and when I came in from work, it had flooded the garden and caused pressure to go way high as well as flushing the whole system with new water. I then bled radiators and used the loop to get back to 1.5 bar but since we've had the problem described in 1st paragraph.

From what I've read, this sounds like the expansion vessel - could it just require air pumped into it or is it more likely broken because of leaving mains water running in for a while? Is this the DHW expansion vessel - the manual implies there are 2 - one for HW and one for CH - hot water one sounds more accessible and I assume is the one with the valve to pump it up that I read about on here? Am I right? Will the PRV likely need replacing too?

Can anyone advise me of what the problem is and how I could go about fixing it?

Cheers.

The rad full of air was in effect an expansion vessel so after you bled it & repressurised system your blr relied on inbuilt vessel @ rear of blr. This will need pumping up but if water comes out of schraeder valve it will be easier to fit a remote vessel

Thanks for the reply... I checked a Schrader valve on the back of the boiler - it's on a big round red plasticy thing which I can only assume is the expanion vessel in question. No water came out which is good so I'm going to pump it with some air - going to get hold of a gauge tomorrow to monitor the pressure and check it's OK before I go wading on it blind with a footpump.

What pressure should this be at and what pressure is it safe to pump air in to?

Cheers.

look ih faq's

Sorry, missed that bit in FAQs - read it now and it makes sense... will have a bash tonight.

One quick question though... see the AAV which I think is in the top left of the boiler, the FAQ says to ensure that this is left screwed open but when I checked mine, it seems to be closed. It's just a small cap thing, similar to the dust cap on a schrader valve - do I just unscrew this a little? What effect does this have? Am I talking about something totally different?

Cheers.

Yes that's it, it should be open a turn or so. They often leak a bit, cheap to replace, 3/8" size though (I think!!)
Check your pressure relief pipe isn't dripping too.