On Sun, 13 Jan 2013 18:43:33 +0000, Dom Ostrowski wrote:

That sounds a rather fast soot build-up to me.

It's not soot, at least not soot as in fine powdery possibly slightly
oily stuff that I remember as soot from the open coal fire when I was a
lad. This is hard brittle black lumps and some very light and crispy
browner bits.

When I was heating this place by woodburner alone (Jotul, similar size,
similar fuel, similar rate of consumption, no backboiler) I swept it
myself twice a year and got out out half a bucket of soot from the
flue, and only light sweepings from within the stove itself.

I think the boiler makes a heck of difference to flue gas temperature,
thus flue temperature and how much tar will condense out. When it was
swept back in Oct I didn't think that much came down, it certainly didn't
sound like much came rattling down. But as I didn't do it I don't really
know.

--
Cheers
Dave.