Expansion Vessel Why does it leak water out of PRV below 3 b

[406lx]

My expansion vessel is being replaced as water comes out the air valve.

However, even when the pressure is below 3 bar there is water that leaks outside, why is this if the PRVis not supposed to open until 3 bar?

Thanks

 

[Terrywookfit]

Either the prv is knackered due to faulty exp vessell or pressure gauge is not working !!

I would guess it is the prv!!

 

[406lx]

Odd, the PRV was changed and only ran a few minutes before I realised the vessel had gone.

 

[bengasman]

Take prv apart and clean, if it is knackered you will see it easily enough. The thin little tube to the gauge gets clogged up easily. Does it go all the way back to 0 when you release the pressure?

 

[406lx]

Took the new PRV off, clean as a whistle and returns to seal. Gauge returns to zero when the pressure is released in the boiler and cuts off the filling loop at 1.5 bar reading.

Will fit my new vessel tonight and take it from there as the vessel was definately faulty.

 

[DP]

The PRV WILL pass at a lower pressure IF THERE IN NO air in the expansion vessel.
If it is full of water, the PRV will jack up long before the gauge reaches 3 bar.

 

[406lx]

Thanks for the reply, that explains it. The expansion vessel diaphragm had split as there was coming out the air valve when checking its pressure.

Hope to have this sorted tonight.

 

[406lx]

Ok replaced the vessel however there is still water discharging outside.

Only thing I can think of is the pressaure gauge, it doesnt really move from 1 bar and has been on the past hour. Checked the nipple on the PRV and it seems to be fully in so there is only minor leakage. Also when filling it stops filling at 1 bar.

Any suggestions?

 

[chrishutt]

The PRV WILL pass at a lower pressure IF THERE IN NO air in the expansion vessel.
If it is full of water, the PRV will jack up long before the gauge reaches 3 bar.

Nonsense. A properly working PRV will not lift until 3 bar is reached.

406lx, if the PRV is working properly and releasing water then the pressure must be above 3 bar, therefore your pressure gauge is faulty.

 

[406lx]

Ok thanks, will get a new pressure gauge.

Does the gauge dictate to the boiler when the filling loop cuts off as it stops filling at 1 bar on the gauge?

 

[Terrywookfit]

No !!
You have to turn it off manually !!
The gauge is knack**d or you have unusually low water pressure!!

 

[406lx]

Water pressure is fairly high here, showers are gravity fed and like a power shower.

Will try the gauge hopefully that will be an end to this.

 

[chrishutt]

hopefully that will be an end to this.

I doubt it.

 

[406lx]

hopefully that will be an end to this.

I doubt it.

Please could you elaborate?

 

[DP]

Chrishutt can you explain why a PRV was passing at 2.4 bar when there was no air in the EV. After the vessel was pressurised without limit, PRV lifted at 3 bar? Boiler was a VCW 242.