COMBI - WORCESTER 240 - KETTLING ?

[willjhunter]

Hi All.

I have a worcester 240 combi which i think is kettling.

This only occurs when dhw is demanded, i could run the dch all day and night no problems.

Ive just changed the pump as this was capoot and recently done a fernox ds40 system clean. The dhw will run for minutes and then all help breaks loose, noises pops bangs etc and then eventually the boiler trips.

What else could be causing this. the gas/heat exchanger has been out and looks clean as far as i can see.

Would a worn diverter valve be causing the problems as Ive noticed that the main central heating feed from the water tank gets hot when this occurs!! (open system)

Please I need some ideas as Im pulling my hair out !!!!!!!

 

[clf-gas]

You say the feed gets hot, does it get hot above the boiler.

It does sound like a problem with the diverter valve. Get a service kit and clean it. DV I mean.

 

[willjhunter]

clf

The system is an open system with a water tank above the boiler with a pipe going from this into the boiler, this is for the ch. like i say this problems never occurs with central heating, only hot water demand. It makes me think that if it was the heat exchanger I would get issues with the CH as well as the HW. After flushing the system the pump went. Either sludge/debris fouling it but when I switched on the CH after the drain and the pump wasnt working I got this issue with the CH immediately as well as the HW. Now Ive got the new pump in again its only HW issue is with. This again makes me think it aint the gas/water heat exchanger.

Back to topic!

This pipe begins to get hot and when the issues arises (kettling) I believe that hot water somehow is getting into this pipe. My only thinking after examining the heat exchanger and replacing the pump would be that somehow the hot water flow is demanding and heating up but the valve is sticking/not allowing enough flow and then causing the kettling due to the heated water not being allowed to flow away quick enough and due to the valve being nacked its flowing into this pipe???

Would this sound feasable?

Any good websites for DV kit or would local plumbing centres stock them as I want to try and get this sorted asap.

Thanks

Will

 

[willjhunter]

To answer your questions yes, sometimes the whole pipe from where it goes into the boiler up to the feed tank gets hot.

 

[clf-gas]

After flushing the system the pump went. Either sludge/debris fouling it but when I switched on the CH after the drain and the pump wasnt working I got this issue with the CH immediately as well as the HW. Now Ive got the new pump in again its only HW issue is with.

So the pump issue was after a chemical flush, to which you thought may of flushed debris into the pump.

To expand on this theory, you may have debris in the DV and possibly in the water to water heat exchanger.

When you open a hot tap can you feel the pipe from DV to HE getting warm, and likewise its return pipe.

 

[Agile]

Yes, check the secondary heat exchanger.

You have a classic symptom of a blockage !

Tony