6" RMH Build

[matt walker]

Adam, I moved your post to a new topic...."new build questions".

[mannytheseacow]

Well, we hit 0 degrees here last night. That's pretty scary to see temps like that this early in the year. I expect it in January and February but not in early December. By 1:30am I had run my hot water tank down into the 60*s putting hot water through my floors and swore I was putting my potbelly back in this morning. I just couldn't bring myself to do it today, though.

The crazy thing is that the sun is out today and even at 0* my solar collectors had my hot water tank back to 110* by 10am. I'm home all day today and already fed 20# of wood into the RMH and I'm just holding the house at 67*.

[rjdudley]

Ok, this is a really applicable and timely discussion.
Matt, 250˚ bench temp? WTF? I'd be freakin' out if my bench got that hot. But, I got to tell you that I've been extremely curious about just how hot a bench can safely be driven to.
Like you guys we've been experimenting with the whole "blanket on, blanket off" scenario trying to guess the best way to run the heater to maximize what it does.
We now get to the point where we keep the bench covered until we reach temps that we begin to feel are too hot to keep blankets on (and those temps are actually probably too conservative) and then we pull the blankets back and let the bench do it's radiating business.
We definitely still have cold spots. Lots of them.
We burn about twice a day for 3-4 hours per burn. That seems to be our sweet spot for the above scenario.
Matt if my bench got up to 250˚ on a regular basis would it be safe to assume that it would NOT be good for my surrounding walls, etc.? I remember you saying that there are concerns about combustibles that are kept at 150˚ being dangerous.
Manny, I understand your feelings about the potbelly.
Oh, what does everyone think about running temps? Would you rather run at say 400˚ for several hours and hope the bench comes up to a good radiating temp? Or, would you rather run at 600-700˚ to try to really heat it up more quickly, but, risk losing more heat out the stack?
Ray

[mannytheseacow]

[matt walker]

Tropical Isle sounds pretty dang good right now! We've been below 20°F for a few days now, this is crazy cold for here. Ray, that was the only time I've ever seen temps like that in my bench. I definitely usually take off the cushions long before then, and it worried me too! Typical is more like 140° with a high of 180°. As it's been so cold I've been heating up the bench then taking off the cushions and it does seem to push more heat into the room. As for temps, I do tend to run longer at 400° on these colder days since I'm really heating with the barrel. I think ideally I'd be trying to heat a smaller, better insulated space, and wouldn't need so much of the barrel heat and could burn shorter, hotter fires, and let the bench do the room heating.

[mannytheseacow]

Last week sometime I something happened with my system and all of a sudden I saw my bench temperatures climb significantly. I thought the bench had hit a new stage in drying or something. I didn't think much of it other than being happy that it was functioning properly- finally!

Over the course of the last week I have noticed that my draw isn't that good. It wasn't noticable at first, but gradually noticed more and more flame creep, that pot I use to cover the logs when I was gone was needed all the time or else it was smoking up like crazy. No more rocket sound. That pot/fire cover was getting so hot I couldn't touch it. Finally, this morning I went to light the fire and no draw at all. Smoking out the chimney, smoking out the feed- no draw whatsoever.

Besides the smoky house, I pulled the fire into a metal bucket and moved the flaming smoking mass outside. I checked the cleanouts- A little dark but mostly clean as a whistle. I pulled the duct where it enters the chimney:

Totally plugged!
This wasn't the hard sticky creosote gunk I used to get with my old wood stove, but rather dry fluffy little balls, almost like drier lint. I pulled almost 2 gallons of the stuff out of the chimney flue and felt a gust of cold air whoosh down. Fired it up- back to normal. Good draw, no smoke. I don't know what this stuff is, but definately going to be more attentive from now on (cough, cough).

[matt walker]

Well, that's new. So weird that what ever it is all collected there at the end, and up 6 feet or so. It's almost like it came down rather than got blown up and stopped there. Condensation running down carrying sediment then drying? Just a wild guess, sounds weird. Glad it's running good now! Saw your temps post, 64 ain't bad to wake up to at all.

[mannytheseacow]

Yeah I'm a bit confused as well. The stuff is light and fluffy like little bits of black popcorn or Styrofoam. I went up on the roof after work and pulled the cap off the chimney and there is a significant amount of gummed up in the chimney vent, too. Needless to say, everything got a good cleaning. I'm guessing it has something to do with the cool air that the exhaust hits as it moves up the cement chimney column, condenses, and falls back down to the elbow in the chimney. The source may be some oils from all the walnut I burn? I'm just throwing things out there... I don't have a clue and am definitely looking for feedback from others that might know the science behind what's going on there. My last stove would create creosote, but not enough to plug the chimney in a whole season.

My old stove would be smoky when it lit up, but once it got burning I would never see smoke from the chimney. I've never had that with my rmh. I just assumed that what I was seeing was moisture and that it would disappear as the mass dried, but I've yet to see that smokeless fire with my rmh? Weird. I don't know if something isn't right with the burn or if it's the wood? I'm not too worried since the bench pipes are clean... but a clean burning stove is most of my motivation for building this thing.

Count my blessings; at least I'm warm!

[matt walker]

Well, knowing how low your exhaust temps are, I'm guessing that what you are seeing is steam rather than smoke. I don't remember looking at your chimney, is it masonry all the way out of the roof and to the top, or does it transition to insulated chimney pipe at some point? Anyway, I've been playing lately with stoves using uninsulated chimneys, and for sure they keep on having visible exhaust when the temps are cold, since the moisture recondenses into steam in the chimney. You have low exhaust temps, even at the thimble, so for sure you are condensing into steam. In other news, related, I've recently acquired test equipment and can verify that these things are burning super cleanly. I'd be really surprised if you could make it make much smoke, especially since we verified you are burning dry wood. Is your bench still running hotter than it ever has, or did that go away once you cleaned the stuff out?

[mannytheseacow]