Central Heating Problem

[help]

Hi,

My brother has a Heat line condensing boiler, when the central heating is on the gauge on the boiler goes round to 3-3.5 bar
the system has been flushed through which mains pressure and filled up to 1bar and rads bleed there is no air in the radiators or pump and the gauge is at 1 bar when cold, when it comes on rads get hot and gauge rises to 3-3.5 bar water starts to drip from pipe out side,when turned off and goes cold again gauge is at about 0.5bar and system needs filling again to 1 bar.
Any clues? been told expansion, and to check vessel 0.5bar

System has 7 rads on 10mm pipe.
System as been flushed but when a rad valve was cracked open water was black, could this be the problem, radiator silted up.

Any advise would be greatful.

 

[davetheplumber]

Sounds like the expansion vessel. Has he checked the pressure on it?

 

[GroundControl]

99% that the internal expansion vessel has ruptured leaving nowhere for the water to expand to 🙁(
try testing the "tyre valve " puss the pin in and my guess is water wwill probably squirt out !!
replace the vessel and you may also need to replace the PRV if this has been passing for some time as this may have scaled up internally

 

[migoplumber]

i agree with expansion vessel problem, test as above.
sometimes its cheaper to leave the old one broken where it is and install a new one somewhere else on the line!

shaun