Worcester Bosch 24cdi issues!!

5 Dec 2012
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United Kingdom
For 4 weeks now we have had boiler issues. We have a Worcester Bosch 24cdi.

Our boiler (after several attempts by engineers) is now working but we still have water dripping out of overflow pipe. The pressure is at 2 bar (black needle) but redneedle is at 1.5. the flow gets worse when CH is on.

When the engineer left earlier there was no dripping out of the overflow pipe... Until we started using hot water again, properly.

We have had a new PC board, fan, switch, gas valve, and pressure cylinder fitted.

Apparently the engineer took out the filling loop. What could be causing this constant drip? The engineer people just can't seem to fix it. I tried bleeding rads but they have no air in.

Any advice or opinions wouldbe greatly appreciated.

Thanks in advance


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Is overflow pipe dripping with CH on or off?
Edit: just reread and realise you've had the pressure vessel replaced, either tube is blocked to it or plate heat ex is passing. (Providing filling loop is disconnected).
Thanks for your reply. Yes it was just after we used hot water for washing up, and then got worse with CH on.

Are any of the above (your reply) anything that I can look in to doing DIY? Obviously not replacing or repairing but could I look for a blockage in pipe? Any idea which pipe and where it is likely to be on the boiler?

It's very frustrating.

What's pressure rise to with CH on at full heat? The black needle should be at 1-1.5 when cold leaving room for expansion when heated, but once PRV (valve connected to overflow) has gone off the once they hardly ever reseat and will always drip so will possibly need replacement now, also why have all them other bits been replaced ?! Was he having a lucky guess moment?
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The black needle is on 2 when cold and I've just turned hearing to 28 degrees Celsius and the black needle has not moved since turning it on (5 minutes ago). God knows, I think they are guessing but building us a new boiler ay the same time!! Although not working.

So you think the valve needs replacing on overflow pipe or the heat exchanger?
Or should I partially drain that system by opening a valve on a radiator (not sure where drain valve is on this boiler)
We have had a new PC board, fan, switch, gas valve.....fitted.
I hope you've not paid for any of those! What were the initial symptoms that first caused you to call someone out? Sounds like you've got a parts-changer on your hands rather than someone with actual diagnostic skills
Our initial call out was for the fact that the boiler kept cutting off and flashing red.

We have insurance with Home Energy Serbices so thankfully not paid for it apart from a monthly fee.

It's really frustrating - I would have though that they would consider it being a faulty pressure relief valve?

One thing I can't Understand is that the pressure in the boiler is not reducing even though it remains to be dripping from the overflow pipe.

Thanks again

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