On Sun, 11 Nov 2012 08:31:38 -0800 (PST), harry
wrote:


The fan in most gas gas boilers is working on a mixture of gas and
air.

I don't follow that, I though it was just an induced draught fan after
the heat exchanger?
If so then it would be no different in effect on the log burner,
primary air causes a combustible gas to be evolved which then burns
out in much more secondary air.

The effect of this is to thoroughly mix them so promoting efficiency.

Which is why I mentioned a fan would aid wood combustion, it can
provide more turbulence than natural draught.

All the larger wood fired systems I worked on had id fans and many had
primary air fans too. The better ones had wide band lambda sensors to
control secondary air and I have never had problems with fouling of id
fan blades. I did have a big problem from a chimney being terminated
with a conventional gas cowl which sooted up.

AJH