Vailant Extotec Pro 28 - pressure loss

[Scott6488]

We have an issue where the boiler is dropping pressure (to a point where the f22 message is appearing) at least once a day.

The PRV and expansion vessel have both been replaced and rads have been checked for any visible leaks.

When the boiler is upto pressure it will run most of the day, but when it stops running (house up to temp) then the pressure drops.

What would you be looking at next?

 

[kidgreen61]

Sounds like a leak under a floor, somewhere where it can't be seen.
Are you sure nothing is coming out of PRV pipe?

 

[Scott6488]

Nothing coming out of the prv.

This has started since we came home to find a damp ceiling. Traced it back to what appeared to be a bad join on a plastic pipe that the trv blows out into. The boiler is in an old airing cupboard and the pipe from the trv sits inside a plastic pile which disappears out of sight

 

[oldbuffer]

1. Photograph of airing cupboard showing bad join might help.
2. What do you mean by ".. plastic pipe that the trv blows out into..."

 

[Scott6488]

1. Photograph of airing cupboard showing bad join might help.
2. What do you mean by ".. plastic pipe that the trv blows out into..."

The bad join has since been repaired, I added that comment as I wasn't sure if it would be of relevance.

With the TRV, we have a small section of copper pipe that come from the trv to the outside of the boiler. As the boiler is in the centre of the house it looks like they have run a plastic overflow pipe into a larger waste pipe

 

[CBW]

Try and isolate the boiler from the system, ideally overnight, and see if the pressure drops.

 

[Harry Bloomfield]

Add a plastic bag fixed over the outlet of the PRV, with an eleastic band. That will collect any water which is ejected. Was the EV air pressure set up properly?

 

[Scott6488]

Add a plastic bag fixed over the outlet of the PRV, with an eleastic band. That will collect any water which is ejected. Was the EV air pressure set up properly?

A new EV has been installed and the pre charge was checked before it was installed.
Noted about the bag, but the will try that tonight

 

[Harry Bloomfield]

A new EV has been installed and the pre charge was checked before it was installed.
Noted about the bag, but the will try that tonight

It reads like water loss as it first heats up, then the fact it runs fine until it cools - which is usually and EV issue.

 

[Scott6488]

It reads like water loss as it first heats up, then the fact it runs fine until it cools - which is usually and EV issue.

Agreed Harry that's why we went down the route of swapping out the EV, unfortunately the problem remains the same.

 

[kidgreen61]

TRV = themostatic rad valve.
PRV = pressure relief valve

 

[Harry Bloomfield]

Agreed Harry that's why we went down the route of swapping out the EV, unfortunately the problem remains the same.

It's not unknown for even new components to be faulty.

TRV = themostatic rad valve.
PRV = pressure relief valve

EV = Expansion Vessel

 

[Scott6488]

So last night, heating wa turned off for a couple of hours, repressurised to 1.5bar and then isolated the flow and return. Just for good measure, placed a bag over the prv pipework.
This morning boiler was sat at 1.2bar and no water in the bag. Does this small reduction indicate a problem within the boiler?

When I released the flow and return this morning there was no sudden rush of water into the pipework making me think that the pipework had held its pressure all night and therefore possibly not a leak there.

 

[Harry Bloomfield]

So last night, heating wa turned off for a couple of hours, repressurised to 1.5bar and then isolated the flow and return. Just for good measure, placed a bag over the trv pipework.
This morning boiler was sat at 1.2bar and no water in the bag. Does this small reduction indicate a problem within the boiler?

A difficult one, because pressure is very dependant upon temperature - your system would have still had some heat left in it when you topped the pressure up, but I would say from that you do not have a leak.

Now leave the plastic bag in place, run the system normally and see if any water is ejected into the bag.

 

[opps]

I used to lose pressure on my rubbish Ocean Alpha 240P because of tiny leak inside the combi. Because the leaking water was so hot it used to evaporate pretty quickly. That said, the loss in pressure was no where near as fast as yours. I only discovered it when I took the cover off.