Boiler pressure

[fabien]

Sorry if it has been asked 1000 times.

What would be the reason(s) for the boiler pressure to reach 2.5/3?

Thanks

 

[brasso1981]

What is the pressure before it fires up?

 

[fabien]

2.5
It would reach 3 when on

 

[dancinplumba]

its too high, should be ideally at 1.2 when cold

 

[secret squirrel]

If its 2.5 when its cold and you haven't topped it up badly then the filling loop is letting a bit of water through constantly. If this is the case check the pressure relief valve outside its probably dripping.

 

[GrahamM]

Your average system would be 1.5 bar when boiler off and system cold. Pressure may rise to 2ish bar when system at full temperature.
As above, you have either put too much pressure in, the filling loop is passing or you may have other issues that an engineer can advise on.

 

[SimonG]

If it's only going to three when the boiler is on and then you are having to top it up when cold then I would be looking at the expansion vessel first. If it's getting to three when cold then it's either the filling loop passing as said above or a potential problem with plate heat exchanger (if it's a combi).

Get somebody to look at it. If you post your location then somebody on the forum may be in a position to help.

 

[fabien]

If its 2.5 when its cold and you haven't topped it up badly then the filling loop is letting a bit of water through constantly. If this is the case check the pressure relief valve outside its probably dripping.

It was set at 1.5 last December and I haven't touched it since then. Don't know how long it has been at 3.
Is it just a question of bleeding the radiators to bring pressure down or do I have to call someone in?

FYI the exchanger was changed last December. There was a thread about it
http://www.ukplumbersforums.co.uk/central-heating-forum/29902-boiler-lockout.html

I had

 

[PlumbBobBob]

yes you can drain a bit of water out of a radiator to bring the pressure down. don't bleed a rad it will take ages, isolate a small rad on both valves and drain it down. when you reopen the valves this will bring the pressure down bleed the rad of air and top up the boiler to around 1-1.5bar and keep an eye on it.