Combi boiler pressure too high?

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We have a combi boiler which is now showing between 2.5 and nearly 3 bar. The pressure release valve is constantly dripping outside. The boiler is all working fine, ie heating the water when needed etc. I also have the central heating to come on every day for about 20 minutes just to keep the central heating going over the summer. The boiler was serviced in February and all was ok. The lights on the front of the boiler are showing the boiler is working fine. I can't hear any funny noises when the boiler is working. I have released the pressure by bleeding a radiator and have put it to 1 - 1.5 bar, but after about 24 hours, it has gone back up to 2.5 to 3 bar. What could be the problem? Any help would be appreciated.
 
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and now the process begins , our crystal balls dont work on Sundays, which make which model ??? would you call a garage and say my car is making a noise ?
 
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could be that the filling loop is letting by, is it the type with the braided hose? if so remove the hose and see if any water is seeping through the valve on the cold main.
could also be the pressure vessel is bust or needs re-charging.
have a Google for recharging pressure vessel, and there'll be some info on how to do it
 
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Thank you for the reply. It is a biasi boiler. Is recharging the vessel something i could do, or is it best left to a gas engineer? If the vessel is broke, is there a rough idea how much they are?
 
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The expansion vessel won't cause the pressure to keep rising.

As said you need to check the filling loop isn't letting by
 
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as advised disconnect the filling loop and see what happens, then read the rest of what I asked you , you have a Biassi ??? which model ???
 
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Have disconnected filling loop(braided hose) and water is dripping out. I also reduced pressure to 1.5 bar. Now, when I turn the hot tap on, it fires up ok, then it starts making a sort of whistling sound, which goes quiet, then a bit louder, then quieter again. When the hot tap is turned off, the noise goes.
 
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Have now lowered the temperature gauge on boiler, and it doesn't make the whistling sound. It goes up to about 80 degrees, and still no whistle, so I assume that it could be air in system?
 
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