Pressure Loss on Ariston Euro Combi boiler?

[MattPy]

I have just bought a house, which has an Ariston Euro Combi boiler. Its been running fine until last night when the pressure dropped below 1.5 bar and the system didnt fire to produce hot water or heat the radiators, I increased the pressure by switching the black stop cock that lets water into the system and it fired fine and heated water and radiators, but the pressure goes down over time and drops below 1.5 bar where it cuts out again.

I can find no leak in the system and there is no evidence that water is getting out of the system anywhere in the house, and the radiators all come on very hot when the boiler fires.

Can anyone help?

 

[Gasguru]

Assuming its the EuroCombi with the grey lower panel then..

The presuure switch is blocked/out of calibration. They are normally set to turn off the boiler at around 0.7 Bar. Replace it.

If the presuure drops you have a leak or the expansion vessel is failing.

Have you checked the presure relief pipe on the outside wall - tape a plastic bag over the end to catch any water drips.

 

[Blasphemous]

My money is on the PRV (Pressure Relief Valve) Letting By MattPy. In normal service the PRV closes without a problem but sometimes the valve is prevented from closing due to debris on the valve seat. Which allows water to leak (Letting By) from the system and the pressure drops. Resulting in Boiler Lock-out until you re-pressurise.

As Gasguru states, have a look outside. There should be a pipe leading from the boiler to outside. This is the Pressure Relief pipe. If you see it dripping from there, there's a good chance its the PRV. It may be hard to spot so take his tip and tape a plastic bag onto the end. Check it after about 2 hours. If nothing there, leave it on over night and check it in the morning. If the PRV is letting by the bag will have water in it.

You'll need a Corgi to Clean/Replace it. A new one should only set you back about £20 plus the labour. About an hour to do the job.

 

[pannierstan]

You'll need a Corgi to Clean/Replace it. A new one should only set you back about £20 plus the labour. About an hour to do the job.

Not forgetting the main reason why the PRV is passing might be that the expansion vessel is flat.

Weve been through this many times on here but the long and short is get some one in.

Stan

 

[Blasphemous]

Not forgetting the main reason why the PRV is passing might be that the expansion vessel is flat.

Weve been through this many times on here but the long and short is get some one in.

Stan

Might be Yeah. Lets be honest, the only way to diagnose the fault truely, is to see and work on the appliance.

As Stan says and I have said earlier MattyPy, get a Corgi. Try and get one 'recommended' by a friend or family. Quailification and does not always mean Competence!