Boiler pressure

22 Sep 2005
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United Kingdom
Hoping somebody in the know can help me with my boiler problem.

I've just put a radiator back on after decorating and refilled the system through the loop on the boiler and then open all the bleed valves to release the air. When I refilled the system I put enough water in so that the pressure guage on the boiler registered 1.5 bar as per the manufacturers instructions.

I went back to the boiler an hour or so later and the pressure guage had risen to 3 bar. I released some pressure from the system (or so i thought) by releasing the pressure valve in the border which has a pipe that goes out through the wall. I thought this had cured it but again the pressure gradually crept back upto 3 bar. I then opened the drain valve on the boiler and and released some more water via a hosepipe.

Again the pressure guage dropped but then gradually rose back upto 3 bar.

I'm obviously doing something wrong - can anyone tell me what. Also, is it safe to use the boiler at the 3 bar pressure?
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It sounds as if the filling loop is/has not shut properly.

Release the pressure, NOT from the PRV, then make sure it is about 1.2Bar and remove filling loop.

You will probably have some water leaking out of the filling loop valve.

Don't use the boiler at 3 Bar, whilst it is not dangerous as such, the PRV will keep operating to release the excess pressure.
does it rise to 3bar and stay there or does it only rise wen the ch is on then drop back down?

from how you have described sounds like either ya fill loop or ya heat exchanger is passing (asuming its a combi), try setting the pressure to 1-1.5 bar and disconecting the fill loop hose.

what boiler is it?
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thanks for the quick replies chaps. The boiler is an ideal mini 28 (combi). I've turned the tap on the filler loop right off but the pressure has still gone up albeit very slowly. The pressure is at just above 3 bar without the heating being on.

At the risk of sounding ignorant, which end of the filler loop should I disconnect, the end just under the filler loop tap or the other end? If I disconnect it, won't the valve just leak onto the floor?
doesn't matter which end you disconnect.
the end connected to the central heating return (22mm pipe) should have a non return valve stopping your sys from emptying, and the side connected to ya cold mains (15mm pipe) should be shut off by a tap (this is what we suspect is letting water through in the closed position)
i would disconnect the side connected to the ch return and position the hose which is still attached to the cold mains into a bucket incase it is passing
right, I think i'm with u so far. Supposing that I disconnect the filler hose and water is still passing through despite the tap being closed, does this mean that the tap needs replacing? If this is the case, I think I'll need to get a pro in. I appreciate that by disconnecting the filler hose it will stop filling the system up but I will still have a leak to deal with.

Thanks v much for all the help so far, it's much appreciated.
If you disconnect the filling loop and the pressure is STILL rising then it means that your heat exchanger has a small hole in it, so the cold mains is is entering the CH circuit through the domestic hot water heat exchanger.

It probably just the filling loop passing though, so you will hopefully just need to replace that not the hx :LOL:
if you disconnect the hose and water continues to come out and fill the bucket up wen the tap is in the closed position you need to replaced the filling loop tap, if wen you disconnect the hose the pressure continues to rise you will need to replace the plate heat exchanger :LOL: simpelz

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