high pressure in a combi boiler

[stephfos]

Hi I have a problem with my combi boiler, the pressure keeps getting high Usually around 1.5 bar but going up to 2.5 bar, I have reduced the pressure by bleeding the radiators but within 24 hrs the pressure keeps going back up, can anyone help???

[matt1e]

hi if the pressure is creeping up when boiler off suspect the fill loop passing
if going too high only when on suspect the expansion vessel

[gucciman]

yes you need an heating engineer !

[pilotlight]

stephfos, Both Matt1e and gucciman are correct.
However, the filling loop should not be permanently connected. Once the system has been pressurised to the correct pressure -- usually around one, to one and a half bar, the filling loop should be disconnected and capped.
Hope this helps.

[stephfos]

thanks for replies really appreciated, filling loop is connected but has a tap which is turned off and only used when pressure drops.... which has been very rare.

pressure only creeps up when heating is on, so if matt1e is correct then it sounds like the expansion vessel....any idea what cost to replace or repair would be?

[pilotlight]

stefphos, You really do need the services of a suitably qualified boiler / heating engineer. The expansion vessel is a vessel that is internally split into two by means of a diaphragm. On one side of the diaphragm is the system water, which is pressurised, on the other side is air, which is also pressurised -- manually. There is a possibility that the vessel may just need repressurising.
It is a requirement of current water regulations that the filling loop is disconnected following pressurisation of the system. One of the reasons for this is to prevent any possibility of contamination of drinking water by the heating system water.
Hope this helps.

[stephfos]

many thanks Pilotlight I shall seek professional advice
have a good new year

[douglasf]

I was trolling through some sites trying to find an answer myself. In the end on my Ferroli system it turned out that merely turning the boiler temperature down (not the thermonstat) cured it as the lower temp created less pressure and didn't expel through the valve. I think this is more of an issue with rad valves which once the rads are up to temperature switch off creating more pressure for the system. Anyway it worked for me and it's free.

[stephfos]

Thanks for that

[robstar2020]

my boiler pressure keeps going up causing it run out the overflow pipe and down my wall any clues