Pressure on Vaillant ecotech624

[Seb1961]

I have a pressure problem with my four year old Vaillant ecotech plus 624 system boiler.

I've just had an engineer round who re-pressurised the expansion vessel.

When I switched the boiler on for heating and hot water in the afternoon  after he left the pressure went right up to 2.8 bar into the red area on the display. To avoid the PRV blowing I switched the boiler off. The pressure then rapidly dropped to 0.5 bar. This is obviously too low and this morning I had to add some water before I could get the boiler to fire up. Then the same happened: the pressure went sky high and dropped back to 0.5 after the boiler was switched off.

There are no obvious leaks anywhere.

Any ideas what's going on?

Seb

 

[popeye2755]

Get the engineer back... It sounds like the expansion vessel is knackered.

 

[Phill Peck]

As above

I would guess the EV has been over pressurised is water coming out of the PRV pipe

 

[Seb1961]

I can't hear any water running away. I don't have an external drain for it.

And Popeye, wouldn't the engineer have spotted a faulty expansion vessel? He re-pressurised it and would have noticed water coming out, no?

How much would it cost to replace an expansion vessel on a Vaillant if it's faulty and would they break down after 4 years?

Thanks.

 

[Phill Peck]

Should last longer than 4 years but depends on condition of system etc

You would expect someone u call to know what they are doing but that is not always the case

Your PRV pipe will be the 15 mm copper pipe on the far right hand side and it is a legal requirement that it has a "visible termination" this can be outside or where connected to a suitable drain an tundish/visable air break must be fitted

The water doesn't come out of the expansion vessel

From what you have described I would say that your expansion vessel is not working so the pressure is rising and the PRV opens

 

[popeye2755]

And Popeye, wouldn't the engineer have spotted a faulty expansion vessel? He re-pressurised it and would have noticed water coming out, no?

Thanks.

EDIT

Sorry, missed the last post!

 

[MANDATE]

Maybe your engineer does not know how to re pressurise a expansion vessel.
There's more to it than just pumping it up.
The vessel might be half full of water and only half the volume of 'air' and this will send the water pressure up to 3bar and operate the PRV.
The vessel must not have any water in it and allow 'air' to take up the full volume