how do you set the pressure on a combi expansion vessel ??

[Gnarly Neil]

I have an Ariston Euro Combi system. I have fixed the gfollowing problems

Leaking Safety Valve. Done No more dripping and pressure loss.

Faulty Air pressure switch causing intermittent boiler failure. OK now.


However I have noticed that the pressure which when cold is about 1.5 bar as suggested rises to about 2.8 bar when hot.

This was not the case previously?? I have checked the system to see if I have introduced an air lock of some kind which may be expanding when the system gets hot, but all rads seem to be getting hot etc some I have ruled that out.

I think that it must be the expansion vessel? I have seen various posts about Expansion vessels but can't find out how to set the correct starting pressure via the valve.

I have depressed the valve breifly to see i water came out. It didn't but the bolier pressure dropped by .25 bar .

Can anyone help me??

 

[MANDATE]

Expansion vessels contain a flexible membrane so the water pressure on one side of the membrane is balanced by the air pressure on the other side.

The pressures on each side of the membrane remains equal and by releasing some air (which is in a compressed state) has reduced the pressure on the membrane and released some of the pressure on the water.
I'm not a plumber, but it would not surprise me if its as simple as a cycle pump to re pressurise. question is at what stage should this be done and what pressure?

 

[oilman]

You must be able to find something, look for expansion vessel and filling loop in September 2003. There are lots of posts there. Other phrases are "two storey" and "0.5 bar"

 

[breezer]

but it would not surprise me if its as simple as a cycle pump to re pressurise

CONGRATULATIONS you win first prize the bg engineer used a foot pump to re pressureise ours

 

[oilman]

Aah, I always thought there must have been an easy way to do it.

 

[MANDATE]

Breezer!
Thank God it's not my problem! I don't have a 'foot pump' or a 'cycle pump'
Now Oilman says in his related posts that it should be nitrigen so what I want to know now is how did bg get the required nitrigen in the foot pump.

 

[breezer]

he didn't (or are you taking the ..... ) it was air but since air is 70% nitrogen.

 

[Gnarly Neil]

Thanks for your help. I pumped up the pressure with a bicycle pump, ( with the correct nitrogen ,oxygen, co2 and pollution mix) This seems to have solved the problem. Pressure no rises by about 1 bar when the systems is fully up to temperature.

Now all I need to worry about is a noisy fan ( with dodgy brushes ) is it worth changing the brushes or swopping out the fan (£50)???