While very pleased at how well the tiny wood stove has been keeping my tiny house cozy these past few days where it has been so very cold (today’s low was -2F and the high was +9F), I was not at all pleased to find smoke streaming out of the flue this evening! I mean, yes, smoke is supposed to come out of the flue — the top of the flue — but it is not supposed to come out of the bottom, which is where it was emerging tonight.
I have no idea what’s going on, as the stove has been in near constant use for weeks and has been performing so well. Tonight, it was burning low and slow while I was out grocery shopping. I came home, opened the air inlet to fire it back up, and I am greeted by a stream of smoke coming out of the bottom of the flue at the arrows.
This fitting at the bottom is the single-to-double adaptor, the thing that connects the cast iron receiver that’s part of the stove to the double-wall flue pipe (stainless steel). Besides smoke streaming out at the seam, I also noticed some discoloration on the bottom of the adaptor (brown/yellow streaks) and what seems like some kind of sealant or cement oozing out, as well.
The flue is composed of a 4″ pipe (that’s what fits into the stove proper), some insulation fibers, and a 6″ outer pipe. At the bottom, there’s a retainer ring that dresses the end of the insulation and helps keep it in place. That’s what has the streaks on it. The inner pipe is what appears to have some ooze dripping from inside.
At first I thought it might have been a smear of cement from when I set the adaptor into the stove’s receiver, but no way would it look like that if I had. A streak from a cloth or a glove from below wouldn’t have sharp edges like that and wouldn’t be emerging on the surface of the inner pipe and not also showing on the retainer ring. I’m convinced this black goo is coming from inside. I’m pretty sure it shouldn’t be.
Speaking of black goo coming from places it shouldn’t, there was also this surprise where the receiver connects to the fire box. There should NOT be a ring of pearls here. There wasn’t yesterday.
I don’t think this is cement having come out of the adaptor-to-stove joint and landing here, since that joint still looks pretty tidy. If this much cement had been ejected, that joint would have to look quite ragged. It doesn’t. The other option is that this is gasket cement from where the flue port meets the stove body. I don’t remember whether there’s a gasket there or not, but quite possibly. If I over-fired the stove, maybe I cooked that cement out? And maybe that’s exactly what happened to the single-to-double adaptor, too? Overcooked and blew a seal?
Fortunately, I have a backup propane heater which should be sufficient to keep me warm with the stove out of service, though it is far less economical and ecological to use it. Still, I gotta be warm.
I have sent these pictures to the stove manufacturer (who has been very responsive and supportive over the course of my purchase & installation) asking for advice. Meanwhile, I shall let the stove cool down completely so whatever service is required I can perform safely. If I need parts, though, that may be a problem. Most of us know by now that global supply chains are all screwed up right now. Things take a long time to get places, if you can get the things at all.
I do have half a tube of cement, though, so if all that’s needed is to re-apply some cement where it has been degraded, I can definitely do that.
And maybe I need a stove-top thermometer to warn me about over-firing, if that’s my problem.
I don’t think it’s related, but there was this interesting scene earlier today:
Yeah, that’s ICE hanging from the bottom of the wind screen on the top of the stove pipe. While a fire is going. Granted, heat goes up, not down, but I’d still have expected the heat of the exhaust to warm the wind screen enough to keep ice from forming. Evidently not when it’s zero degrees out.
Let me preface this update with I’m new to owning and using woodstoves so there are perhaps very basic things I simply don’t know. I’m learning quick though!
The stove people think that all the goo is simply creosote and the reason I was getting that and the smoke had to do with draft issues. I’m not entirely convinced – the path for the smoke didn’t make sense to me if it were a draft issue – but thinking about the whole scene, I realize that I had stuffed the fire box, so the entrance to the flue was a bit obstructed and there was a very thick layer of coals at the bottom, so the air intake was also a bit obstructed. Taken together, it is entirely feasible that I had drafting problems, causing a hot box that couldn’t breathe. How this resulted in the creosote string of pearls I do not understand, but maybe it had to do with poorly burning wood high in the fire box and without good draft to carry it all up the flue, whisps made it out around the collar and over time formed the pearls.
I still can’t explain the seemingly downward expression of smoke from the adaptor. There’s nothing above it that could supply that smoke – but clearly there must be, that would be the same path taken by the creosote seepage also seen there.
I dismantled the flue enough to sight along its entire length, looking for any obstructions or heavy buildup. Nope. Clear sailing end to end and just a smidge of buildup no thicker than the thickness of a sheet of office paper. Definitely no constriction. There seemed to be plenty of exhaust even with the ice hanging off the chimney’s wind screen, so I don’t think that had anything to do with it, either.
A bit of a mystery all around, though the contributing factors of bad draft and a stuffed fire box seem to be the driving causes.
I fired the stove up again today, being mindful of both those things, and it lit fine and drafted well and there’s no smoke coming into the house and no creosote bubbling up around the collar or oozing down from the adaptor after running it all day. So okay, back to normal, nothing is broken/clogged/etc. Just mysterious results from user error, it appears.