Hi. My 15year old Worcester Bosch 24 suddenly started rising in pressure when the heating was on and blew the prv. I put a new prv in and checked for pressure at the expansion vessel schrader valve. Nothing came out- no air or water. Re pressurised vessel to .7 bar and everything is running sweet as a nut. My question is: how could this happen and is it a sign that my vessel is on its way out? I have prepared myself to install an external vessel as I know these are a royal pain to get out. Second question: if I do plumb in an external vessel, do I have to disconnect the original vessel and blank off or can it just be left alone. Thanks for any info on this.
Worcester Bosch 24 expansion vessel
- Thread starter Hawaii2004
- Start date
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The valve isn't a perfect seal. Air will leak out over a period of months/years. Same as happens with car tyres and similar.
Did you leave a drain down point open when you re-pressurized the Expansion Vessel ?
Hi yes. It's running fine now I've re-pressurised. Just wondered why it lost its air. Thanks.
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Your expansion vessel should be re-charged every year when you have your boiler serviced , using large companies that will never look at it , or doing the supposed service yourself, or no service at all, you work it out
Whilst most people get their boilers serviced, it is usually only the self employed to do the job more properly and check the air pressure setting.
But there is a simple test that any home owner can easily do to check if it is correct.
With the system cold, read the pressure, normally set to 1.0 to 1.5 bar.
Turn on heating and see how much the pressure increases. In most cases, where there are not too many rads, the pressure will only increase by up to about 0.3 bar.
If it increases by a lot more then the EXV air pressure needs to be checked. In most more modern boilers this is within the boiler case seals and so not a DIY job so should be done by an RGI at the next service.
If the pressure increases a lot when it reaches about 2.5 bar the PRV is likely to start to open and let some pressure out. If the system water is a bit dirty then the PRV may not initially reseal. Although many will after a few days, even up to a week.
Tony
But there is a simple test that any home owner can easily do to check if it is correct.
With the system cold, read the pressure, normally set to 1.0 to 1.5 bar.
Turn on heating and see how much the pressure increases. In most cases, where there are not too many rads, the pressure will only increase by up to about 0.3 bar.
If it increases by a lot more then the EXV air pressure needs to be checked. In most more modern boilers this is within the boiler case seals and so not a DIY job so should be done by an RGI at the next service.
If the pressure increases a lot when it reaches about 2.5 bar the PRV is likely to start to open and let some pressure out. If the system water is a bit dirty then the PRV may not initially reseal. Although many will after a few days, even up to a week.
Tony
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