Ariston Euro Combi not reaching pressure - any ideas please

[EliTom]

Hi - first post here so hopefully I have done it right!

Hopefully someone can give me some tips or guidance with this one.

Basically have a 10 year old Ariston EuroCombi SX 20 Mffice boiler and all was working fine until I took two rads of the wall to decorate.

The rads valves were closed off and no leaks occurred during the two days they were off. the heating worked normally.

Put the rads back on, filled them and bleed the whole system to be sure.
Later that day heating stopped working and the system pressure was down to zero. Topped it up back to 1.5 bar as per Aristons manual. Within about 20 - 30 mins the pressure was back to zero.

First thing I did was check the two removed rads for leaks. All dry.

Next I suspected the expansion vessel. I had had this loose pressure a few years ago. An yes it was down to 5psi - should be about 15psi - 1 bar.

So today re-pressurised the expansion vessel with the system drained. And it seemed a bit better but still would not rise above 1.5 bar system pressure when running hot. Normally the system runs at 2.5 bar hot.

So today went out and got a new expansion vessel, fitted it and no difference. The system hold cold pressure at 1.5 bar for a while then slowly starts to fall off.

The system will just hold the 1.5 bar fill pressure, but does not rise up to
the normal 2.5 bar.

I have taken the front cover off the boiler and there is some scale around some of the joints but all are dry.

One last question - should the wet side of the expansion vessel be full of water. The old unit I took out was empty, but when I disconnected the pipe from the chw return there was water in it?

I guess I will have to leave it to go cold overnight to see what it really
does fall to, but before I call in a Corgi guy and have to pay top dollar is
there anything else I can test / check?

thanks for reading

EliTom

 

[petit_pablo]

The pressure not rising above 1.5bar when hot is not an issue, better that than 2.5bar.
Outside there should be a pipe coming out the wall about a metre or so under the flue from the pressure relief valve. Is this dripping / wet? If so, thats where your water is going. This would be my 1st port of call

 

[chrishutt]

Agree with petit pablo. You've been over pressurising the system. 2.5 bar is far too high and when hot the system will reach 3 bar and start to release water through the PRV. This will fail to seal properly after frequent use due to debris on the washer.

 

[EliTom]

Sorry should have said that I have put a receptacle under the overflow pipe - nothing there - bone dry.

Also the pressure has now fallen to 0.5 bar from 1.5 (heating was turned off)

Any other ideas please?

tia

EliTom

 

[petit_pablo]

Theres possibly a leak somewhere then. Water pressure has to go somewhere.
Is it possible that a joint under the floor could have been damaged when the rads were removed?

 

[chrishutt]

Then you have a leak somewhere. Isolate the heating circuit and see if the pressure still drops.

 

[EliTom]

Agree with petit pablo. You've been over pressurising the system. 2.5 bar is far too high and when hot the system will reach 3 bar and start to release water through the PRV. This will fail to seal properly after frequent use due to debris on the washer.

Hi thanks for the tips.

However without wanting to appear ungrateful for any help, the Ariston Installation and Servicing Manual states that the system pressure should be set at 1.5 bar. The operating pressure in the tech data in the same manual states 2.5 bar.

That is the conditions this boiler has worked to for the last 10 years.

Thanks again

EliTom

 

[EliTom]

Then you have a leak somewhere. Isolate the heating circuit and see if the pressure still drops.

Very valid point - off to do that now - at least the hot water should work

Thanks

EliTom

 

[bengasman]

Did you top up when system was hot or cold? you must compare pressure at identical circumstances. Easiest is either fully cold or fully hot, including all rads

 

[EliTom]

Did you top up when system was hot or cold? you must compare pressure at identical circumstances. Easiest is either fully cold or fully hot, including all rads

Initially it was filled cold, all rads bleed then topped back up to 1.5 bar.

Left it for half an hour and the pressure had fallen to about 1.2 bar. Topped up again to 1.5 bar, checked each rad for air again then checked it was still at 1.5 bar. It was.

Then ran the heating for a hour or so in which case the pressure normally rises to 2.5 bar - normal working pressure for this boiler,but the working pressure did not rise above 1.5 bar and infact started to fall. So turn the heating off and left tit to cool a bit by then the pressure was down to less than 0.5 bar and then the DHW would not work

Hope this makes sense - his is really frustrating me - it either a coincidence that something else has just failed or it some thing really stupid and I just don't wan to get fleeced by a random fitter from the yellow pages - sorry that is not saying all central heating guys are out to make a fast buck, just want to try and find the answer myself first.

Thanks

EliTom

 

[EliTom]

Then you have a leak somewhere. Isolate the heating circuit and see if the pressure still drops.

Very valid point - off to do that now - at least the hot water should work

Thanks

EliTom

Ok topped back up to 1.5 bar about 20 mins ago and closed the inline valves on the chw flow and return.

The pressure is now down to 1 bar !!!!

So I guess his says the leak must be in the boiler.

Maybe I should call Ariston / MTS Group tomorrow?

Anyone any other ideas to check before I give up and get a man in ? !

Thanks

EliTom

 

[chrishutt]

Check the AAV. They often leak. Have you looked around inside the boiler? The leak could be inside the combustion chamber.

 

[EliTom]

Check the AAV. They often leak. Have you looked around inside the boiler? The leak could be inside the combustion chamber.

Yes I have looked inside the boiler, and all appears dry.

there is quite alot of green/blue scale around some of the pipe unions, but all are bone dry.

I have opened up the combustion chamber and again all is dry.

I would try and "tweak" each pipe connection but worried about cracking a joint and making things worse.

I will try and post some images of the scale. Maybe that is significant

Thanks for your time and help - much appreciated

EliTom

 

[EliTom]

OK I spoke about green / blue scale on pipe unions.

Here are some images.

Yes they look bad but they are all bone dry. Is this something to worry about on a 10 year old boiler. Is it scrap ?

Thanks again all

EliTom

 

[chrishutt]

No sign of an active leak there. What about the Schrader valve on the expansion vessel? If air was leaking from that it would appear as a drop of the system pressure. Also are you sure that the flow and return iso valves are fully shut? If so, you must be losing water somewhere from the boiler. It can't be that difficult to track it down.