Yesterday I went back and fitted the stove all over again. I wasn’t happy with the way the flue was installed, even though it was fitted the way it was designed to be.
The single skin stainless steel flue pipes, fittings and caps (chapéu) on sale here aren’t the most ideal flues from the point of view of efficient stove operation as the thin metal leads to rapid cooling of the combustion gases, causing condensation of water vapour and creosote accumulation at an accelerated rate. I’d already swapped my initial choice of 130mm pipe for 110mm before installation to increase draw and flue temperatures, but the nature of the pipe is such that 20mm diameter probably doesn’t make a massive amount of difference. (Though what do I know? I’m not a heating engineer.)
These prefabricated flues are designed to slot together such that the narrow end of the interlocking sections is at the top end of each pipe section and the sleeve ends downward. This means that whenever it rains heavily, the inevitable small amount of water that finds its way into the flue adds to natural condensation from combustion and trickles down the inside of the flue, dissolving creosote on the way, and eventually finding its way out of the joints, no matter how well sealed, thanks to the corrosive nature of creosote. Creosote has a really pungent smell. It’s just not nice to live with whether or not you subscribe to its reputed carcinogenicity. And it leaves nasty crusty black stuff all over the outside of nice shiny flue pipe.
So I decided to dismantle the whole installation and turn the flue pipe sections the other way up. This was a simple matter from the stove to the top of the flue as the stove already had a step-down adaptor fitted that was still just small enough to take the narrow end of the flue pipe as well as the sleeve end.
Getting the chapéu to fit was another matter. Fun? Not! Going back to the hardware store and swapping it for a smaller or larger diameter one wasn’t an option because it was Sunday and they’re not open. Also they don’t have a smaller diameter than the 110mm I’m using, only larger. A hacksaw or tin snips were required. I don’t happen to have either. And it was Sunday. What to do? Coping saw and an old blade. Not ideal, but it eventually did the job. Only then did I think about the possibility of calling on neighbours to borrow something more suitable. D’oh …
With the chapéu fitted to the inside of the flue pipe and bolted in place, the rest was straightforward. Stove fired up again and drawing superbly. Yurt warming and drying nicely. No leaks. No nasty smells.
I’m now wondering whether it would have been better to fit the chapéu to the outside rather than inside of the flue, but I’ll see what happens with the creosote build-up. It can always be changed at a later date …