Greenstar 24i possible Expansion Vessel problem

[rick85]

Hi all,

Got a W.Bosch Greenstar 24i junior.

Been having trouble lately with CH pressure dropping to zero continually after each use. Having placed a carrier bag over the outdoor pressure relief pipe I found that this was collecting a large amount of water and obviously is therefore the location where the system is loosing pressure.

I checked the expansion vessel pressure. This was quite low so i topped it up to the Manufacturer recommended 0.75 bar after de-pressurizing the CH system first.

I then refilled the CH system to 1bar having bled all rads as part of the process.

Re-powered the boiler and turned on heating with CH level set to 5. As the system warms up the pressure rises to just 3bar at which point the pressure relief outlet starts to slowly trickle water.

So even with the pressure in the expansion vessel set correctly I still have water coming though the relief outlet.

My understanding is that this should not happen (stay dry) when functioning correctly? If this is the case, Does anyone have any ideas or suggested checks to see where the fault may lie?

I have an engineer coming to look at this but not until next Friday. If there were a simple fix or even somebody that can give me the heads up on the likely work that will be required before the engineers visit that would be appreciated.

Thank you for reading and any time taken to reply..

Cheers.

Rick85

 

[Gasguru]

Probably expansion vessel hose is blocked...system could be full of muck. Also could be gauge partially blocked indicating incorrect pressure.

Given these issues AND the fact that the pressure releif valve will need replacing you might want to consider calling out Worcester on a fixed price repair. The PRV replacment is often a pig of a job requiring the bottom end of the boiler to be removed.

You could drain 3 or 4 litres of water from a radiator (leaving the top full of air)...that will give the system some expansion untill the problems are resolved.

 

[rick85]

Thanks for the advice gasguru. Not too bothered about cost or effort to fix it. I'm on a no excess contract cover for boiler and CH system. I Have payed a small fortune for this contract over the past three years with no major service calls / repairs required to date.

The engineer came out Feb this year for similar problem and he said that by pumping up the expansion vessel he has resolved the problem.

Over the summer when the CH has not been used it has obviously become an issue again. This is why i've topped up the EV pressure before their scheduled visit to see if this resolves it. Obviously it hasn't.

Just want to be sure i'm aware of all the work/checks I would expect the engineer be doing to make the boiler function correctly when recharging the pressure alone does not appear to provide a permanent fix.

Thanks for your time.

 

[Gasguru]

Be aware that most insurance schemes do not cover sludge in the system...so a blocked expansion vessel hose repair may not be covered....and any insurance company having to replace the PRV on these will use any small print to worm their way out of the contract.

 

[rick85]

Thanks again.

Am i correct in understanding that there are both 'insurance' and 'breakdown cover' schemes as alternatives?

If so how might the 'non-insurance' scheme differ in the above situation?

|Cheers.

 

[MANDATE]

Any reason why the air pressure can't be checked while heating is on and water pressure rising.
If the hose is blocked then the air pressure set to 0.75 will remain at that.