In article .com,
"Neil" writes:
I have been told I need to replace the secondary heat exchanger on my
Potterton Combi 80 due to limescale stopping the HW from remaining hot
(CH is fine)

As the boiler is approx 5-6 years old, would money be better spent on a
new condensing boiler?

Is there no way of removing the limescale rather than purchasing a
brand new exchanger?

I cleaned up a friend's one a few months back. It was quite easy.
That was a Baxi 80, IIRC. The instructions will tell you how to
remove and replace the heat exchanger. Watch that when you release
the pressure, the water doesn't spew out over anything important
such as the circuit boards, gas valve, etc.
Buy a tub of Furnox DS-3, dissolve some in warm water, and keep
pouring through the heat exchanger until it stops fizzing. You
will likely need to mix up fresh solution several times (each
time it goes blue, IIRC). Try to avoid getting any undissolved
crystals of DS-3 into the exchanger, and flush it out well
afterwards.

Flush out the other side too with a strong water jet -- it can
fill with black crud which floats around in older heating systems
(particularly if you didn't have enough inhibitor at some time).

--
Andrew Gabriel