Proper functionality of a pressure relief valve

[jrtrrror]

Hi. Just wondering how a properly functioning pressure relief valve operates.
Does it have it's its own mechanism that detects when the pressure is above 3bar? Or does in rely on the water pressure sensor? The two don't appear to be linked in any physical way.
Also, when a correctly operating valve does 'open', does it release pressure quickly, in a large dump of water. Or does it release the water slowly?
Ta.

 

[Deleted member 32524]

The prv is a spring loaded device that the water pressure forces open st about 3 bar.

 

[jrtrrror]

Thanks for your reply DuncanM.
Does it release the water in a large 'dump' of water and then close. Or does it release the water slowly. Obviously, if operating correctly.
Thanks again

 

[Riley]

It will release as quickly as it can until correct pressure tolerance is achieved. May I ask why???

 

[jrtrrror]

You may
Haha. Our boiler has been losing pressure, quite slowly over a week or so. And then, two days ago, very quickly and the boiler switched off with a E119 low pressure code. I noticed that the discharge pipe connected to the PRV was leaking at a connection. Strange, because ideally there should be no water in that pipe unless the PRV was leaking. I also, noticed that the automatic air valve was, leaking from its plastic headed screw. (It was slightly open). I repressurised the boiler, after which I closed the automatic air valve. I then sat and watched the gauge as the boiler fired up and began heating the rads. I noticed that the needle rose through the gauge quite quickly. In probably less than ten minutes, it was in the red, passing 3 bar, hovering around 3.5 bar. I went outside and sure enough the PRV discharge pipe was leaking water. Quite fast. I think I was expecting, to hear the valve open and dump a lot of water, reducing pressure to a point that the boiler would recognise a too low pressure and subsequently switch off displaying a E119 code.
Thanks for showing interest.
I like a good mystery and like to understand what's happening.

 

[townfanjon]

Not my favourite part of a boiler .

 

[shyguy2005]

You may
Haha. Our boiler has been losing pressure, quite slowly over a week or so. And then, two days ago, very quickly and the boiler switched off with a E119 low pressure code. I noticed that the discharge pipe connected to the PRV was leaking at a connection. Strange, because ideally there should be no water in that pipe unless the PRV was leaking. I also, noticed that the automatic air valve was, leaking from its plastic headed screw. (It was slightly open). I repressurised the boiler, after which I closed the automatic air valve. I then sat and watched the gauge as the boiler fired up and began heating the rads. I noticed that the needle rose through the gauge quite quickly. In probably less than ten minutes, it was in the red, passing 3 bar, hovering around 3.5 bar. I went outside and sure enough the PRV discharge pipe was leaking water. Quite fast. I think I was expecting, to hear the valve open and dump a lot of water, reducing pressure to a point that the boiler would recognise a too low pressure and subsequently switch off displaying a E119 code.
Thanks for showing interest.
I like a good mystery and like to understand what's happening.

Need a gas engineer in to check something else that’s causing the rapid rise in pressure when on heating.

 

[jrtrrror]

Thanks.
What are any common causes for a rapid rise in pressure?

 

[Riley]

Yes there are common faults however we can’t discuss them because they are a safety feature of the boiler and we have a no DIY Gas Appliance Stance

 

[jrtrrror]

Hi shyguy.
May I ask what makes you suggest there is a rapid rise in pressure. How long would it ordinarily take to rise from cold (actually the boiler was displaying water temp at 40c) at 1.5 to 2.5 bar on a properly functioning boiler?

Sorry. Just trying to understand.
My brother was ripped off by a GSE recently. Spent loads of money, without success. When another plumber came, he correctly diagnosed the problem and sorted it in no time.
I don't want to be victim to my own ignorance.
Thanks