"Christian McArdle" wrote in message
t...
Can you explain how you calculate efficiency - is it for example :
Given the amount of heat ( in say joules ) that is released by the
burning
a
specific quantity
of gas, find the amount of heat transfered to the water and take the
quotient ?

It is far more complicated than that. In fact, under the calculation
method
used, it is even possible to get more than 100% under certain conditions.
However, it does approximate the potential absolute efficiency in
translating fuel energy into useful heat energy that may be distributed
around the system. See www.sedbuk.com for details.


So this calculation may give an efficiency of greater than 100% - if so, I
believe this is breaking the
well tested empirical laws of thermodynamics. ( Can any physicists help, my
memory is bad ). The boiler manufacturers should immediately publish this
result :-) I suspect that that, rather than this being the case,
the boiler is nowhere near 100% efficient - the obvious example is the fact
that they all chuck heat out
the flue - even the condensing ones.

What I would be intersted in is :
- A sensible definition of efficiency
- the reason why modern boilers claim such a big efficiency increase over
the older designs - are you comparing older non-condensing boilers with
newer condensing designs.

I couldnt find the calculation details you mention - where is it on the
sedbuk site ?

Steve