Glowworm compact 80e boiler pressure keeps rising.

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Hoping someone can help!

I have the Glowworm compact 80e boiler and the pressure keeps rising to 3 bar and then the relief valve kicks in, here is what we have tested to rule out so far.

The filling supply/loop is ok, have taken and left this off to check there is no small leak letting water in.

Expansion vessel was checked by a plumber, no leaks, water coming out, all seems fine and was pumped up/recharged.

Basically, we fitted a new radiator, and the problem came about after this and a prolonged period of the heating not being in use. When we fitted the new rad and had to let some water into the system to get the pressure back up, (the wife) didn't shut the valve off completely and the pressure went up to 3 bar before i noticed and caused a tiny leak in the new radiator. I let some pressure out, leak stopped, figured all was good.

Then a few days later noticed the pressure went back up to 3 bar, so i let some pressure out again, and it was fine for a few days, then pressure went back up.

I figured out it was when the boiler kicked off, or was turned off over night was when the pressure seemed to be going back up, and now it does it right away every night.

When my plumber friend came round and checked the expansion vessel and recharged, it was fine again for a couple days, then same issue again after turning down/off over night, pressure back up to 3 bar.

The hot water has also seemed temperamental whilst this has been happening, shower/taps taking longer to heat the water than usual?

does it sound like the plate heat exchanger? or is there anything from putting the new radiator on it could be? we checked all the pipe work for leaks and it seems ok, it all seems to have started from that initial mistake of leaving the filling loop open!

to check if it the plate heat exchanger is the issue, do i just turn off the cold water in supply to the boiler and then see if the pressure rises once i have let some out? or do i turn off the mains water supply which is near the boiler and not use any water to check?

would i leave the heating/boiler off as well when doing this, and not use any hot water??

Just want to be sure so that i don't waste my friends time, and my money in unneeded parts!
 
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Drop the pressure, turn off boiler, isolate the cold and see if the pressure still rises. If it doesn't turn the iso valve back on and see if it goes up. If it does it's probably the secondary HEX
 
it does sound as though you may have a pinhole in your plate heat exchanger, on the cold water inlet to your boiler there will be an isolation tap/valve, turn this off at night before going to bed and see what the system water pressure is in the morning, it would be helpfull to also use your heating while this valve is closed, if the pressure rises with this valve closed then you have an expansion problem, if it doesnt rise you have a plate heat exchanger problem, make sure that the filling loop is physically disconnected during all tests
 
Drop the pressure, turn off boiler, isolate the cold and see if the pressure still rises. If it doesn't turn the iso valve back on and see if it goes up. If it does it's probably the secondary HEX

So, just to check, drop the pressure right down or back to 1 bar or so? do i have to turn off the cold water at the mains or the cold water in supply on the boiler? and also, when turning back on, i just leave the boiler off right?

Pressure is slow to rise so i'll have to leave it off a while, just want to make sure i am doing it right!
 
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I'd drop it lower than 1 bar as it will be easier to see any rise. Just shut off under the boiler. If you turn the boiler back on the expansion of the water as it's heated will make it difficult to tell if there is a problem.
 
Ok, so before i checked the plate heat exchanger, i wanted to give the filling loop one final test and leave it off for a long time, as the pressure does seem to be increasing slowly.

After giving it 24 hours, and making sure the boiler kicked in, was off for a while, and the pressure went up, low and behold there is a very slight leak coming out there, so the valve must be faulty and only happening with the heating/cooling of the system or something.

Hopefully this simple fix sorts it now, thanks everyone for the replies.
 

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