Frequently having to top up water pressure in Vaillant combi.

[ReganAndCarter]

Oops, was typing, missed your post. Yes, the ex-Vaillant guy who saw it last year said as much about the boiler, he was quite passionate about it and the most fair and professional person I've ever had found in any trade. You can find him of you search for Vaillant service London.

Not much room for an external EV, works have to be mounted behind a kitchen cupboard or in the underside of a worktop if it has to be near the boiler. Hopefully it might be a pump up job.

OK, as Footprints has said, depressurise the ch system/boiler, then try pumping up the EV to .75 Bar. Leave for an hour or overnight, and re-check EV pressure. If still .75 then EV will be ok. If it's ok, repressurise ch system/boiler to 1.2 Bar. If however the EV loses pressure in the test period, it's time for a new one.

And if you're using Mark from Vaillant Service London, you are lucky to be using some of the most knowledgeable people in the country when it comes to Vaillants. A Turbomax Plus maintained by V S L is a great combination and should ensure a few more years of economic and reliable service of your heating and hw.

 

[Johnking]

OK, as Footprints has said, depressurise the ch system/boiler, then try pumping up the EV to .75 Bar. Leave for an hour or overnight, and re-check EV pressure. If still .75 then EV will be ok. If it's ok, repressurise ch system/boiler to 1.2 Bar. If however the EV loses pressure in the test period, it's time for a new one.

And if you're using Mark from Vaillant Service London, you are lucky to be using some of the most knowledgeable people in the country when it comes to Vaillants. A Turbomax Plus maintained by V S L is a great combination and should ensure a few more years of economic and reliable service of your heating and hw.

Yes, Mark is fantastic!

 

[Johnking]

It would be ok for OP to remove case. as it's only a cover, not sealed on the Turbomax Plus.

Yes, the EV is behind the burner, easily accessible from the top.

 

[Johnking]

Update...

Today the boiler pressure cold had dripped from 1.5bar to avoid 1.2.

I drained some water until the boiler pressure gauge said zero. Then I attacheda car foot pump with gauge to the EV. Pressure was zero. I pumped it up to 0.75bar. When I then looked at the boiler gauge it read 1.2bar. This only makes sense to me if the gauge is reading low... But anyway I didn't need to up up the boiler.

Started it up and the pressure stayed below 2bar.

So I'm not sure what the status is now. Why did the boiler lose pressure overnight? Is my EV knackered or was it just needing pumped up? What next? Keep an eye on it?

 

[ReganAndCarter]

Update...

Today the boiler pressure cold had dripped from 1.5bar to avoid 1.2.

I drained some water until the boiler pressure gauge said zero. Then I attacheda car foot pump with gauge to the EV. Pressure was zero. I pumped it up to 0.75bar. When I then looked at the boiler gauge it read 1.2bar. This only makes sense to me if the gauge is reading low... But anyway I didn't need to up up the boiler.

Started it up and the pressure stayed below 2bar.

So I'm not sure what the status is now. Why did the boiler lose pressure overnight? Is my EV knackered or was it just needing pumped up? What next? Keep an eye on it?

If the pressure is staying below 2 bar when ch is up to temp, it sounds like you may have successfully re-pressurised the EV. When the EV was flat and your boiler was over pressurising, it may have caused system water to be released out of the pressure relief valve through the copper pipe that goes through wall to outside.

Often this system water has debris and rust particles in it (from internal corrosion of rads, etc), and these can get in the seat of the PRV and stop it from sealing properly. The valve may weep causing water to drip from the pipe outside. Tie a bag over end of pipe to see if this is the case or watch end of pipe with ch running and up to temp. If it is dripping, the PRV may need removing and cleaning or replacement. Not a big or expensive job.

 

[Johnking]

That's encouraging!

I'll try it at a higher boiler temp, as that was when it went to 3bar. And I'll do the PRV experiment