mepellet
Minister of Fire
I believe class a or at least the one I installed was rated for up to 1000 continuous use. I might be wing though. If that's right and the chimney is installed correctly, it shouldn't be dangerous.
Creosote fire!....
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So I gather from this that you have "never" darkened the glass on your stove, or when you run a brush down your flue you've never had any accumulated creosote to remove? If so it is quite admirable, however I wouldn't say it was normal.
Lots of posts in this forum of people showing the amount of accumulation they removed out of their flues, and even more posts about people asking, or telling, how they clean the their glass.
It's true that dry wood and proper cleaning practices will keep creosote deposits to a minimum, but when people start claiming white glove clean flues my tongue starts slipping into my cheek. I do my best to maintain burn dry wood and burn properly, but there are times when things are beyond my complete control. The burning dry wood part is easy for me as I have a good supply of it in the woodshed, but the proper burning practice is not something always in my control.
For one thing, anytime we let the fire go out, and start it again, we are starting with a cold chimney. Anytime you have a cold chimney you are going to get more creosote condensation than normal, maybe not much, but you definitely get some. Also, if you have ever been in the situation when you just got a fire going, and it's really not in the groove yet where you know you can dampen it down for an extended "clean" burn, but you must leave the house. Well, I have. As much as I dislike it, I will sometimes dampen it down sooner than I should, because I know it's safer to dampen it down, and risk a smoldering fire, over leaving the damper open and over firing the stove well I'm gone. Also I have 3 other people in the house who I sometimes depend on to run the stove when I'm not around, not one of them is a member of hearth.com, soooooo I think you know where this going???
I don't think I'm alone in saying life sometimes gets in the way with the desire to burn as cleanly as possible, and the result is sometimes I (or somebody) will get darkened glass on the stove, and I know for a fact that if I have dark glass "creosote deposits" on the glass, it goes without saying I'll also have some in the lower part of the flue as well. I could clean the glass manually, or I can just do what most people do, and burn as usual and let the fire burn the creosote off. Now, if I'm burning the creosote off the glass, what is happening to the creosote in the lower part of the flue? Maybe I'm going out on a limb here, but does this seem familiar to anybody ? or does everybody else always burn as white glove cleanly as BB?
It could very well be I'm the only one on hearth.com who ever gets dark glass on my stove, but I don't think so..
Anyway, to answer the OP question, creosote starts burning off my glass, and I imagine in the flue as well, when the flue temps (measured with a probe inside the flue) start reaching 800-900 F.
Knowing that I (we) can't always burn as cleanly as I would like is one reason I try to be diligent about regular cleaning my flue. I see no danger with a light layer of creosote burning off the lower part of the flue, but knowing that is happening once in a while I want to be sure I don't allow enough to build up to the point where it could ever become self sustaining chimney fire.
No magic claimed. Thin layer of soot in the pipe and it is cleaned out twice a year most seasons. The only glaze or crunchy stuff is in the four inches above the top plate up top 21' up. The part exposed to cold wind. What isn't in the pipe is anything that is gonna burn off with that "daily hot fire". Glass hazes on occasion and gets wiped off.
And I bet that here in the Tropics of Virginia I have a heck of a lot more cold starts in a season than most members here. A good part of the year the stove is cold started twice a day. Again no magic. Small stuff start up fire to build a coal bed and then loading the big stuff on it.
Point being, I am the sloppiest wood burner on the planet and have never seen any evidence of any use for the burn the crap out of it once a day stuff. If it makes some people feel better to do it, fine. But teaching it as a part of how to burn I will question every day of the week.
And I bet that here in the Tropics of Virginia I have a heck of a lot more cold starts in a season than most members here. A good part of the year the stove is cold started twice a day. Again no magic. Small stuff start up fire to build a coal bed and then loading the big stuff on it.
Point being, I am the sloppiest wood burner on the planet and have never seen any evidence of any use for the burn the crap out of it once a day stuff. If it makes some people feel better to do it, fine. But teaching it as a part of how to burn I will question every day of the week.
The guide lines for flue temps are well established and have been for a long time, they have not been corrected for the cat stoves or the new EPA stoves to my knowledge, so on a single wall pipe surface is 250 to 450 (guides lines not absolute) with translates to probe temp (as tested my Pen I think) of 500 to 900.
400 to 550 probe (200 to 275 surface) should fall in those guides for the most part, I still wonder if you can run a lower flue temp with a secondary burn EPA stove then a pre EPA stove.
800 probe is not high at all as 450 surface is considered in the safe burn zone which would be 900.
I rountinely hit 600 with my summit as thats where it runs on start up and reload which is about 1200 internal.
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I cruise in those ranges - good dry wood as well (ok the odd sizzler - but not often) and the chimney so far (4 years) stays very very clean. That's with a straight-up thru the roof install. The higher temps for me are more to do with startups. Interesting discussion here around whether you need that hotter burn every day, etc. - I never really thought about it, but for me, it's kinda moot as these hot fires on startup are just the way my stove / setup runs best. I do a lot of cold starts as a mostly weekend burner, so I walk into a cold place, and get good heat fast by letting it have lots of air - it will quickly climb past the cruising point, then I start to dial it back. Guess what I'm saying is the hotter fire on startup is just a routine that works well for getting up to temp fast in my situation, and doesn't scare me as long as I'm not off in another room making coffee or otherwise asleep at the switch
- 1000 deg and climbing does get the heart started a bit...The start up is the dirtiest part of the burn but since the fire is one of the hottest after it gets going it burns clean, have you ever noticed the fire box is dirty at the first part of the burn and then clean as a whistle a little while later, thats whats going on in the chimney also. Turning it down too quickly can be a problem though.
I start fires most of the year do to the way the house heats (big heat sink) and I had hardly anything in the flue, even the cap is spic and span, my flue temps do tend to run fairly high leading to the clean chimney.
I would for a person who is burning correctly such as BB, what he has is normal, a lot of creosote and black glass is not.
Nope - your temps are above the creosote producing temps. My cruise temps are similar. You mentioned the key ingredient also - good dry wood.
This is the point that I'm making, if the firebox gets dirty sometimes, and after a good hot fire it seems cleaner, then you are burning something off, that something is basically creosote. If you have it in the firebox, or on the glass then it goes without saying you'll have a little in the lower part of the flue too, and it will also get burned off the next nice hot fire you have.
I agree with BB that you shouldn't be depending on extra hot fires to clean your chimney, just normal clean burning practices should be all you need, but the fact is, you can, and most of us will, get some small amount of creosote formation sometimes from certain things like cold start ups, turning down the damper too soon, etc... but it will burn off next time you burn a "normal" fire. I wouldn't call that small amount of creosote burn off on your glass, or stove, or even in your chimney, abnormal. and it's certainly not a chimney fire, it's just "normal" burning. A chimney fire is a self sustaining thing, and requires a certain critical mass of buildup to be a potential problem, that's where clean burning practices and regular chimney cleaning come in, to reduce the likelihood of that happening. Both will "help" eliminate the risks, both are important, but neither should be totally depended on alone.
IMHO the burn hot once a day came from when people smoldered there fire overnight with airtight stoves (bad way to run a wood burner) so the phrase does not apply for the newer cleaner burning stoves.
I do think I misunderstood what your point was, but as bag of hammers and you said its just normal burning practices for many of us.
I do think I misunderstood what your point was, but as bag of hammers and you said its just normal burning practices for many of us.
This is a really interesting thread. I realized when you are talking about the normal cycle of "burning off" anything accumulated since the last "hot" cycle (startup or whatever), it may not necessarily mean a "small" chimney fire. The glass is a good example - you can stand there looking at the glass watching it clear up, but it's not like it's on fire or even glowing around the edges as it disappears - it's almost like it's being vaporized off. I bet the same thing is happening in the flue. It may be getting cleaner but there is not actually any fire.
Even if you can't see the flue thermometer, or if you can't have one such as on an insert, there is one sure way to make sure you are burning right.
Use the glass on the stove - if you see full bright flame, then you are burning correctly. Obviously as you enter the coaling stage, the flame is gone, but so as well are the ingredients that create creosote.
Bright flame, clean flue.
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Exactly. The flue thermos were a tool for stoves where you couldn't see the fire.
Well some are still haveing problems and they can see the fire, posts come up all the time.
Oconnor and BB make a good point. To add to that, I think as you get some time under your belt, you start to get a feel for all the other cues - the amount of heat radiating out the glass, the speed of the "pings and pops" (warming up or slowing down), even a bit of smell from some dust burn off that wasn't in the air a half hour ago, etc. You kinda get to know the sweet spots etc. I imagine for the folks who've been doing this for decades, with a wide assortment of stoves, chimneys, etc., it's so much second nature that some of the gadgets probably seem a bit silly.
But having said that, for $15 and 5 minutes of my time, I get a nice sanity check (for me, anyway) - just another visual cue. Until I have a brain fart and run the brush down and mangle it
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But having said that, for $15 and 5 minutes of my time, I get a nice sanity check (for me, anyway) - just another visual cue. Until I have a brain fart and run the brush down and mangle it
.No doubt and I dont need it but my flue temps are all over the place and its nicer for the wife.
I thought I was the only one stupid enough to do that.But having said that, for $15 and 5 minutes of my time, I get a nice sanity check (for me, anyway) - just another visual cue. Until I have a brain fart and run the brush down and mangle it
as you can see i burn a (smoke dragon) my defiant. when i first started using it bh.c (before hearth.com) i was smoldering the fire and had no idea not having a window to see my fire. now i use a stove top thermometer and life is different. within 3 weeks of burning i had a massive chimney fire. but with all i know about burning and my stove and the nature of the beast i still get creosote in the chimney. mind you it is 80 % less than before but i still have buildup. it's not from my burning technique or i don't think it's my stove but it's my chimney. 8 x 12 clay flue. outside chimney and no insulation. no matter what i do i get creosote. when i burn as a updraft stove i run it at 600 stove top or 350 to 400 smokepipe. when it runs as the down draft with secondary burn the stove runs at 500 stove and smoke pipe at 325 to 350. last night it was cruising at 500 stove. look out side at the chimney and no smoke just heat waves. i start with a top down start every time time twice a day. and i still get creosote and running a brush down a chimney with a 1/16 of a inch of tar at the top and crust lower does nothing for the tar.
my point is sometimes you could be doing your best and creosote will still happen. like what was said earlier in this thread you may not have a full blown chimney fire but extended runs of no smoke and just heat will start to crust up and bake off buildup. i agree burning ultra hot for a hour once a day does nothing. nothing but clean off the connector pipe if needed. but as far as what temp does a chimney fire start that is always different. with my experience with chimney fires and i have had lots it's not how hot your running your stove it's stuffing in some cardboard or opening up the door when you have a half loaded stove and the flames go up the pipe for that quick minute that carries a spark up the chimney it attaches to the creosote and the rushing air up the chimney creates a amplifier and puff. here is where having a shut off to my secondary air pays off. if that never happens i don't have a chimney fire. but getting that stuff off the chimney is not going to happen right thru to the next burn season unless i (i don't mean to start off a big argument with what i'm about to say) burn a creosote sweeping log at the very last fire. that in my experience is the only thing that dries up the tar enough so that before i start the next season i brush the chimney and most of it comes off.
i have people around here that burn low and slow all fall winter and spring. there is so much creosote in their chimney that it is leaking out the seams of the cement block. he never sweeps his chimney and never has any chimney fires. it baffles me.
just my .02 cents worth
frank
my point is sometimes you could be doing your best and creosote will still happen. like what was said earlier in this thread you may not have a full blown chimney fire but extended runs of no smoke and just heat will start to crust up and bake off buildup. i agree burning ultra hot for a hour once a day does nothing. nothing but clean off the connector pipe if needed. but as far as what temp does a chimney fire start that is always different. with my experience with chimney fires and i have had lots it's not how hot your running your stove it's stuffing in some cardboard or opening up the door when you have a half loaded stove and the flames go up the pipe for that quick minute that carries a spark up the chimney it attaches to the creosote and the rushing air up the chimney creates a amplifier and puff. here is where having a shut off to my secondary air pays off. if that never happens i don't have a chimney fire. but getting that stuff off the chimney is not going to happen right thru to the next burn season unless i (i don't mean to start off a big argument with what i'm about to say) burn a creosote sweeping log at the very last fire. that in my experience is the only thing that dries up the tar enough so that before i start the next season i brush the chimney and most of it comes off.
i have people around here that burn low and slow all fall winter and spring. there is so much creosote in their chimney that it is leaking out the seams of the cement block. he never sweeps his chimney and never has any chimney fires. it baffles me.
just my .02 cents worth
frank
fbelec, unless I missed something it sounds like you have a handle on the situtation and know what you are doing, flue temps look good, out side non insulated chimneys are tough to deal with.
Had a friend who had an outside block chimney and he could not keep the condensation out of it, I suggested he build a insulated chase around it and the problems went away and the stove worked much better.
Had a friend who had an outside block chimney and he could not keep the condensation out of it, I suggested he build a insulated chase around it and the problems went away and the stove worked much better.
Does this mean a metalbestos chimney is more prone to condensation since it's in direct contact with the outside air? I've got 13' of exposed pipe outside. Could install a chase, but it would be very tall and difficult to brace. I guess there's only so much you can do.
My Dad had an early 80's Arrow stove that he used for 30 years. Single wall pipe (elbow) into brick hearth/chimney. When he'd light a new fire he'd let the Condor thermometer go right up to 900F. The needle was pinned. He'd let it fire this way for 10-15', then turn it down. Based on what I've read here in regards to single wall temps, sounds like my Dad was well over the temp limit. Thankfully, never had a chminey fire in 30yrs.
900 would make my butt pucker but my condar is way off after about 500 or so, maybe was only an actual temp of 750 or so with a 900 reading.
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