Expansion vessel

[captain_pugwash]

Folks,
I've trawled the posts and it seems my Glow Worm 30si is exhibiting symptoms that may point to problems with the expansion vessel - that is the cold pressure of 1 bar shoots up to 2 bar when hot and although the prv supposedly cuts in at 3 bar I have drips coming out of the pipe from the prv.

In the past the cold pressure used to be the same as the hot pressure so it does seem that something in the boiler is wrong and the posts seem to indicate that I need to 'top up' the expansion vessel - is this something that is a 'user' task or do I need to call a heating engineer?

Any thoughts appreciated,
Andy

 

[scatmanjohn]

Sounds like either the pressure relief valve is faulty because it should not be dripping at 2 bar. Or the pressure gauge is faulty and you have more pressure than you think.
The fact that it go's from 1 bar to 2 bar when heating up is perfectly normal.
You say that it used to be the same cold as hot which is a bit strange and again could point to the gauge being faulty.

 

[Gasman1015]

The pressure will flucuate. If set at 1 bar cold, it will rise to about 2 bar on full power, working pressure of most combi's is from 0.5 to 2.5 bar and is normal.

Leaking PRV will mean constant topping up of pressure.

If you have a problem with blocked or split expansion vessel , then the pressure will rise rapidly until the PRV operates and removes excess pressure.

 

[compheat]

Check the air valve on the expansion vessel (looks like a tyre valve) press the pin down if water comes out its knackered, if air comes out check with tyre pressure guage it should be .75bar i think. if not let water pressure out of boiler and then top up expansion vessel using suitable pump.

 

[scatmanjohn]

compheat wrote:

Check the air valve on the expansion vessel (looks like a tyre valve) press the pin down if water comes out its knackered, if air comes out check with tyre pressure guage it should be .75bar i think. if not let water pressure out of boiler and then top up expansion vessel using suitable pump.

The water in the boiler needs removing BEFORE you check the pressure in the expansion vessel also the system needs to be open to atmosphere whilst recharging the vessel

 

[captain_pugwash]

thanks for the advice - I have an external vessel and so do I still need to drain down the boiler before putting pressure into it?

Check the air valve on the expansion vessel (looks like a tyre valve) press the pin down if water comes out its knackered, if air comes out check with tyre pressure guage it should be .75bar i think. if not let water pressure out of boiler and then top up expansion vessel using suitable pump.

 

[JPC]

yeap

 

[scatmanjohn]

captain-pugwash wrote:

thanks for the advice - I have an external vessel and so do I still need to drain down the boiler before putting pressure into it?

The system needs to be open to atmosphere when checking and recharging the vessel. The fact that it is external makes no difference

If its only going up to 2 bar and releasing water from the prv then the expansion vessel is not the fault.
Try turning the red knob on the prv a couple of times, it will click shut as you turn it. It will either stop or get worse

Give it a ago and then get back to us.

 

[compheat]

Sorry if i didnt make myself clear on my last message