Worcester Bosch repeatedly cutting out and going to reset

Hi Forum members,

We have a problem with our 7 year old WB Greenstar 24 or 28i Junior (not sure which one it is as there is nothing on the boiler to distinguish) and already had a plumber specialised in WB boilers here several times who cannot find the fault.

The boiler initially cut out after a while of running hot water, running two tabs or the central heating at the same time. The blue light is then normally off and flashes up once followed by two flashes of the red reset light.

The plumber changed the PCB which seemed to make a difference in the first 1/2 hour and at the next visit adjusted the CO2 content to within the limits which hasn't helped at all in so far as the central heating is concerned. Well, we now can have a 4 minute shower (easy with short hair!) - if at all - provided the boiler system is cold. If not, it doesn't last at all and goes into reset pretty much immediately when the tap is opened. The heating doesn't last either, it cuts out pretty quickly too now - I am actually sitting in a freezing cold house as I'm typing.

There is also an anomaly with the green flame light. It sounds as if the boiler is igniting and heating up but the green light for the flame doesn't come on until later ... that's if it get's a chance at all before the boiler goes into reset mode.

The helpline at WB doesn't seem to have a clue what the cause is either. The pressure is ok, the system does not seem to lose or build up pressure anywhere in excess of the normal.

We have already spent some £300, have now a replacement PCB laying about (but the money out of the pocket) and the plumber has other jobs to go to.

Has anyone out there come across this or a similar problem and can help us?

Thanks a lot in advance!

 

Thank you! I will ask the plumber tomorrow if he checked all of the above, although I assume he's done so. Would a change in the gas pressure not be noticeable also on the gas hob?

Yes, CO2 levels are ok, they were within the 5% levy above the recommended max and he's brought them within the recommended min and max levels.

There are few more points that might be worth knowing: I have noticed a decrease in water pressure last year end of August and sometimes the water coming through (noticeable in the shower) has like little, barely noticeable interruptions, not a continuous smooth flow as before. Also noticeable is that just before the boiler cuts out the flame goes out but there is still hot/warm water for a little longer before it turns cold.

Furthermore, since about two weeks the water pressure decreases almost to a trickle when the washing machine takes water - never made a difference before, not even just before the problems started (during the Easter holidays) and the intervals of the boiler working are getting shorter now, i.e. the problem seems to get worse.

The other half just had a shower and initially it cut out twice (the green light/flame goes off - the boiler makes also like an accelerating noise before it goes off -), on the third attempt it actually stayed on until he finished, in between though the flame went off, water got cold, but then the flame came back on (boiler has a mind of its own). ... luckily the boiler is just outside the bathroom so I got the warning scream ...

If I can think of anything else that is out of the normal I'll post it.

Thanks!