Worcester Bosch 37 Cdi makes a really strange noise

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Got a problem with my Worcester Bosch Greenstar 37 Cdi combi.

I believe the system is around 10 years old and was already in the property when we purchased it.

The system was partially drained down today in order to fit a radiator. When the plumber came to re-fill the system the filling valve wouldn't allow water into the system so it was swapped out for a new style valve. Instead of having a key, this value has a small blue switch you can pull towards you to fill the system.

Following refilling of the system, the boiler gave code F7 and wouldn't run. It then appeared to run normally so the plumber left. After around 30 minutes I went to look at the boiler. It was now showing code AE.

I've attempted to restart it a few times but each time it makes a really strange "groaning" noise. The temperature gets up to around 47 deg., the flame light goes out and then the fan spools down. The water temp then drops really quickly to around 30 deg. and the system either does nothing or shows code AE again.

Pressure is currently just over 1 bar and I've bled all the radiators. I can hear water tricking down the condensate pipe every so often so I don't think that's blocked. Not sure what else to look at.

I've uploaded a video demonstrating the noise here:


Just wondered if anyone has any thoughts on what the noise could be and what could be wrong with the unit?

** The unit is currently powered off at the mains and the cover has been replaced. I have not attempted to work on the unit. The cover was removed purely to allow better recording of the sound. Thank you for your understanding. **
 
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I powered the boiler back on this morning. After about 10 minutes of groaning and displaying a symbol like -||- it started to work again.

It now delivers both hot water and central heating.

I would be really interested to know what that groaning sound was if anyone knows. It certainly doesn't sound normal?

I've got to get a gas engineer back in to replace the cover on the boiler and test for leaks so it would be handy to give them any clues as to if something needs replacing.

Thanks again.
 
The -II- symbol is the condensate trap filling, it will do this everytime you cut and restore power, perfectly normal, not sure what the noise was though
 
It's been working fine now for the last two days.
Really not sure what the issue could have been.
 
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For anyone finding this with a similar noise from their boiler the problem was a blocked heat exchanger.

The boiler had been serviced but the engineer had not cleaned out the heat exchanger and it had become blocked.

In the end it was impossible to unblock it and I had to get a new boiler.

The take away from this is to service your boiler and check the engineer performs all of the required service items.
 
New he-ex means new boiler?

Crikey.
I can't recall the price of the unit but it seemed expensive with labour vs replacing 10+ year old unit which may have been getting towards end of life.
 
I believe so. The last engineer tried to clean it out a very flat sort of brush in between the internal fins.

That presumably dislodged material as it made things worse.
Standard service procedure
Look at the manual, guy did what the book asked
 
I believe so. The last engineer tried to clean it out a very flat sort of brush in between the internal fins.

That presumably dislodged material as it made things worse.

That would not be part of a service, but adding inhibitor really ought to be, though not. Which why so many come on here, with blockage issues.
 

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