Worcester 28CDi RSF - heat exchanger problem?

My ten year old 28Cdi has started to have a problem with the hot water. The symptoms are as follows:

* Central heating works perfectly
* When switching on a hot tap, the machine will produce hot water for 20 seconds, then shut off the burner, then start producing hot water again. The cycle will continue for as long as the hot tap is on.
* When the burner shuts down, the demand light is still illuminated, and the machine shows no fault codes
* Just before shutdown, the central heating pressure needle flickers 3mm back and forth.
* I swear the hot water has started to smell of something strange. The wife disagrees.

After a search of the forum, I suspect the water to water heat exchange is leaking, or got a pin hole, and so the hot water system is boiling through to the central heating circuit, and vice versa? Is this possible?

I've also seen a lot of posts where the exchanger gets blocked. We're in a heavy limescale area, if that's important.

Thanks

Gary

i suspect that the heat ex just needs a clean out or replacing, not a job for the faint hearted on these boilers but ok when you`ve done a few

garyo said:

My ten year old 28Cdi has started to have a problem with the hot water.

We're in a heavy limescale area, if that's important.

Click to expand...

Your heat ex certainly isn't holed. The scaling is the problem

Thanks chaps.

If it's the water to water exchanger, then I had to remove that when I replaced the diverter valve last year, so I'm pretty happy to give that a go.

Does it make sense that it can just need a clean out, if it's sending pressure spikes through the central heating circuit?

Edited to say : is cleaning it out feasible if it's scaled - using descaling agents etc? Looks like ~£60 to buy a new one, so worth a go if it's possible.

Cheers

Gary

Okay - I've just bought a new water to water exchanger, so I'll give that a go!

Problem solved - a new exchanger did the trick.

Gary

ha ha replyed to wrong post, too much sun and beer.

What are you on about ? the thread is two years old and nothing to do with solid fuel/gas boiler link ups.