whisky-dave wrote:
[snip]

I've no idea, but when it comes to burning wood I always dry to find
'dry' wood rather than 'wet' wood which has just been cut from a tree
or wherever
it was when still living.

The point about condensing boilers is that the water that is being
condensed isn't from wet fuel (mostly) it is a product of the combustion of
the fuel. Methane (natural gas) has the highest ratio of hydrogen to carbon
and is ideal for condensing boilers. After that, most fuels tend to
approach a ratio of hydrogen:carbon of 2:1 with the exception of fuels like
coke, anthracite and charcoal that are close to 100% carbon.

So if a condensing boiler can be made to work with oil, it should be
possible to make one work with wood. The reason that it is not done us more
to do with tar and acids in the flue gasses from wood burning than it is to
do with the water content of those gasses.

And of course that for these fuels the efficiency improvement cannot exceed
2/3rds of that achieved for methane.

However this is still way better than "Harry" seems to believe is possible.

This document seems to sum it up in 8 pages :-)

http://marioloureiro.net/ciencia/ign...t/ragla91a.pdf

It's a useful analysis, but it doesn't touch on water vapour emissions at
all that I can see in my quick scan of it.