Vaillant Boiler CH pressure increases fast

[GNServices]

Hello,
I have a vaillant boiler, the system is filled to approx 1bar.
The filling valves are in the closed position.

When the CH is on, the pressure increases relatively fast, after 15minutes it will have reached approx 80C and 2.5bar, when the CH is turned off, the pressure will return to 1bar (eventually). Water has came out of the PRV sometimes when the CH has been on.

Sounds like could be the expansion vessel but dont want to get someone in to look at it or play with it myself unless someone could confirm (or give a different theory),

Any help would be great,

 

[ALCPlumbing]

Expansion vessel probably needs re-pressurising. Worst case scenario it has split and needs replacing.

 

[ALCPlumbing]

Use a pump with a pressure gauge. Check manufacturers instructions for exact pressure. I think it's like 0.8bar or thereabouts. If water comes out when you attach pump then you will need a new one.

 

[ALCPlumbing]

Oh and drain down first. You can just drain boiler buy closing service valves with a an Allen key on the flow and return connections to boiler. There is a drain point on each of these connections.

 

[ALCPlumbing]

Before draining down just push in the valve on expansion vessel to see if water comes out.

 

[GNServices]

Use a pump with a pressure gauge. Check manufacturers instructions for exact pressure. I think it's like 0.8bar or thereabouts. If water comes out when you attach pump then you will need a new one.

Just any pump such as a bike pump?
According to the manual it is 0.75 bar

 

[ALCPlumbing]

Yes it has a tyre valve on the vessel. You need a pump with a gauge. Take black cap off vessel valve and push pin in with a small screwdriver. If water comes out then the diaphragm has split as it should only be air in that side of the vessel. It will need replacing. Hold it for a few seconds. If no water comes out then you will need to drain boiler as explained before. Once drained pump up to 0.75 bar and re-open service valves. Top up pressure as required.
Come back on here if it needs replacing and someone will talk you through this if I'm not here. Plenty of knowledgable and helpful people here at all times.
J

 

[GNServices]

Hello, Im back,

Water immediately came out of the expansion vessel when the valve was pressed (system still pressurised to 1bar).

The part number on the expansion vessel in the boiler already is 181050, I can't find this on ebay, I searched for (the model) ecomax 824/2e expansion vessel and a few came up, part number 181051, can anyone clarify this is a suitable replacement?

Also can anyone confirm the method of replacing the expansion vessel?

Thanks

 

[Bunnyman]

Ffs get someone in, just because water comes out the shraeder valve does NOT mean its knackered, it's common on the vaillants, ALC looks new, check the FAQ

 

[GNServices]

just because water comes out the shraeder valve does NOT mean its knackered

Not according to the FAQ as you mentioned,

"If water comes out when you press the central pin, you need a new PV"

That seems like a pretty broad statement.

Please explain how water would be where air is supposed to be in the expansion vessel without the expansion vessel being damaged?

Its worth to mention at this point that I dont think it has been serviced since 2002 according to the service labels on the boiler and that for the last 6 months it had been standing.

Thanks,

 

[Bunnyman]

The vaillants tend to let by when flat through where the seam is . When the tank is repressured the seal reseats in the seam . I reckon at least 20% of the ones i do hav water in em.

 

[GNServices]

The vaillants tend to let by when flat through where the seam is . When the tank is repressured the seal reseats in the seam . I reckon at least 20% of the ones i do hav water in em.

So what you're saying is, the expansion vessel air pressure COULD have dropped so much over time that water has managed to seep around the seal into the air side?

Would I be right in saying then, that to test this, I could continue to press the valve, and if the seal was intact, the water would eventually stop coming out? If so, at this point, could i try and repressurise it with air (with the system drain so at 0 bar on the dial) and then check the pressure again in a few days?

Thanks,

 

[GNServices]

Anyone?