I'm looking to replace my old central heating boiler with a standard (i.e.
not combi) condensing boiler. I will have it installed by a professional,
but want to be more informed about available boilers rather than just accept
what the heating engineer offers.
I have heard that the heat exchanger (HE) on condensing boilers can have a
limited life, that cast iron HEs are to be avoided, aluminium are ok (ish)
and that stainless steel HEs are best. Anyone have any views?
I've also heard that Potterton are unreliable (for condensing boilers) even
though my old (non condensing) Potterton has served me well for nearly 35
Any other points tpo watch out for?
Does anyone have any recommendations (or otherwise) on makes/models of
Very wise. People tend to fit what they know or whichever promo
programme is the best this month.
That's basically it.
They are a shadow of their former selves.......
Manufacturers in Germany and Holland have been making them for 15-20
years and are at 4th generation products in most cases. Therefore
the better products are made in or are designs from these countries.
Typical good products:
Your installer may have heard of the first two. The second two are
A lot of the newer Aluminium heat exchangers are coated to protect the
substrate metal. Works fine as long as the coating is not scratched. Once it
has been damaged then you are wide open to corrosion. Stainless Steel is the
way to go in my book
I would go along with what you said... (ali heat exchangers ought to be
fine if silicon coated).
Look for one with a single heat exchanger rather than one that has had a
secondary one bolted on - this is usually an indication of an old design
that has been updated to operate as a condensor rather than been
designed that way from scratch.
Also look for a downward firing burner. This will prevent it being
exposed to either as much soot or acidic condensate.
To comply with building regs you may have to upgrade your boiler
controls, and fit a fast recovery cylinder if you don't already have
one. You will need TRVs on all rads except the one in the room with the
main stat. If the house is big you may need to zone the heating also.
The ones Andy mentioned are usually very well regarded. Some of the ones
from Ideal like the icos seem good as well.
I have a cast iron cored boiler still plodding away after 30 odd years. It
may be that the newer boilers are more efficient but this is generally
achieved at the expense of longevity i.e. thinner (but more efficient heat
exchanger cores), nevertheless with today's fuel prices a more efficient
core may be preferable even if it is necessary to replace the boiler a
little more often than would be otherwise needful. Condensing boilers have
corrosion problems since parts of them are subject to "condensation", hence
enhancing the corrosive effect of the flue gases.
I would doubt if even the stainless steel boilers are made with the heat
exchanger from top grade materials and thus the rate of corrosion will only
be slower than other cores and not zero.
More correctly -poorly designed condensing boilers suffer corrosian
problems. A well designed one will use materials that are not affected
by the (mild) acidity of the condensate, and a layout that places
critical parts out of the path of any collecting or falling condensate
(downward firing burners etc).
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