Vaillant VCW Sine 18 (again)

[Roger60]

Hi guys,

A new problem on my vintage boiler - pressure drops to zero when CH is off, and the PRV dumps water outside (into plastic bottle on the overflow pipe). Topping up via the filling loop seems to go very quickly.

Am I correct in thinking that the expansion vessel is not pressurised, or is knackered? Trouble is the boiler was nicely fitted next to a wall on the LH side, therefore access to pump it up is impossible. So presumably the easiest solution is to fit a replacement EV. But I don't know where this has to be in the system (as near the boiler as possible?), and exactly where it fits into the CH pipework. And what size is required, 8 litres - is size critical?

I'm in the hands of you expert folks again for advice. This boiler is not going to die (yet)! But whoever (Agile?) said these boilers usually end up with several problems is a genius!

Thanks in anticipation,

 

[45yearsagasman]

Fit it on the CH return pipe as close to the boiler as possible. As for "Genius" that may be a bit harsh.

 

[Bunnyman]

U know where I normally park lol, yes as he said

 

[Roger60]

Hmm! This morning I found the pressure was at 2.5, with the CH off. This was after I topped it up from 0 to 0.8 before going to bed. The CH was off during the night and nobody used DHW.

I gently opened the PRV and the pressure reduced to just under 2, and now it appears to be dropping very very slowly (still no CH on). Any ideas why this should be so?

On the question of an external EV, the nearest I could fit one is about a metre pipe run from the PRV - would this be OK? And what about the original EV - does this have to be disconnected or can it just sit there looking pretty?

Somebody tell me I don't need a new boiler . . .

 

[Agile]

The external EXV can be fitted anywhere convenient on the system but ideally on the return connection and best with at least 1m of 15 mm or 400 mm of 22 mm tube supplying it to prevent hot water getting into it.

It should be at least 12 litres if a house.

The boiler EXV is pretty ugly really. It can be left full of water.

You don't need a new boiler yet. Well not quite yet!

Tony

 

[Roger60]

Got a new EV, fitted on the return, all works fine - no loss of pressure and heating seems to work better than before.

Thanks again to you experts, much appreciated.

 

[Agile]

Well done!

Another Sine 18 given a reprieve!

Tony