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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> ideal classic boiler looses pressure https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1287711454 Message started by mikev521 on Oct 22^nd, 2010, 2:37am

Title: ideal classic boiler looses pressure
Post by mikev521 on Oct 22^nd, 2010, 2:37am

Hi guys im new to the forum and need some advise.

Ive got an ideal classic boiler that looses pressure.

No matter what pressure i set it to, it always drops to half a bar. this never stops it from working but until recently its always been constant at around 1.5 bar. I first noticed it when i removed the bathroom rad to decorate. I thought it was due to the thermostatic valve not holding very well, but guess it wasn't after all as fault still there with new rad connected back in minus the thermostatic valve.

I've read some posts that mention the expansion vessel or the pressure relief valve. Any suggestions as to what it might be??

Many thanks for reading this post.

Mike.

Title: Re: ideal classic boiler looses pressure
Post by CWatters on Oct 22^nd, 2010, 9:13am

Let the system cool and repressure it. Check the PRV outlet. If water is coming out at 1.5 bar then the PRV is probably faulty.

If not then turn it on and watch the pressure guage. If the pressure climbs upto 3 bar and _then_ water comes out of the PRV it's probably the expansion vessel. The expansion vessels job is to allow the water to expand as it's heated. Without an expansion vessel (or with a faulty one) the pressure can increase until the PRV opens. The expansion vessel might only need represurising or it might need replacing. If the expansion vessel is burried deep in the boiler it might be cheaper to add another one on the outside of the boiler rather than replace the one inside. You can leave the faulty one in place if it isn't actually leaking water.

It could also be both the expansion vessel and the PRV. Once a faulty expansion vessel starts causing a PRV to open the PRV tends to be susceptable to leaking.