Worcester 28CDi RSF - Increasing Pressure

4 Mar 2007
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United Kingdom

The overflow / discharge pipe from our 5 year old Worcester 28CDi RSF started dripping this morning. I've checked the boiler and the system pressure gauge has increased to 2.9 bar (heating off). The filling key is out, grey filling knob firmly shut off and the CH / DHW both appear to be operating OK.

Would this suggest the Water to Water Heat Exchanger has seen better days and needs replacing / cleaning? If so any ideas of the cost of a replacement and where to order from?

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shut your mains stopcock, lower pressure back to 1.5 and run your heating, see if it rises.

if not sounds like your heat exchanger passing water to primary side.
Yes the dhw hx's are a common fault on these for some reason.
Isolating the mains supply to the boiler has identified the DHW heat exchanger as the problem. Anyone care to recommend a supplier for a replacement part and the likely cost? I assume they come with new o-rings/seals?
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Its odd how these are unreliable. I have changed more on those than all other models.

I seem to recall the trade price is not much below £100. Quite easy to change but dont remember them coming with any seals but I have always made the old ones work OK.


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