On 15 Oct 2006 15:39:53 GMT, (Andrew
Gabriel) wrote:

I don't know this model, but why not descale it?

I descalled a friend's one from a Baxi using Furnox DS-3.
Dissolve some DS-3 in a large jug of hot water.
Stand the heat exchanger in a washing up bowl to catch
the descaller, and pour into the hot water side of the
heat exchanger slowly. Be prepared for violent descalling
spitting out the acid and acid spray. When you've poured
it all through, empty the heat exchanger out into the bowl,
transfer back to the jug, and the pour through again, until
the heat exchanger stops fizzing. If the descaller goes blue,
it's used up -- discard and mix up some fresh.

I did try descaling it once - but only with domestic supermarket
descaler. It fizzed and bubbled but didn't unblock it. I've never
tried "DS-3". Where can I obtain that in suitable quantities?

But I think these heat exchangers can also become blocked by rust and
sludge on the other side (non-tapwater) side of the exchanger, can't
they? That's what a corgi reg'd plumber once told me was wrong with
mine, anyway. He pointed oit the bits of black stuff inside the
exchanger and said "that's iron oxide that's blocking it" IIRC. Of
course, he might have been feeding me a line of s**t just to flog me
an overpriced heat-exchanger....

Thanks,

Jim D