Crazy/Scary draft issue....I think.

[Todd]

Sounds like that grate could be the problem. That stove was designed to burn wood or coal and probably more tuned for coal since the air comes up from the bottom. Once you cut off the air and loaded it full, got her going good it was starved for air and gulped some down the chimney or through the seams (back puffing)

 

[certified106]

My stove has the shaker grates for coal burning in it also and I dont see how replacing that with something more solid would effect that stove much at all. The bottom air intake on your stove isn't supposed to be opened at all when you are burning wood as it is more designed for those who want to burn coal in the stove. If your draft is sufficient the side air vent should be more than you ever need to make adjustments to the burn intensity. it really sounds like you are having some sort of draft issue if you are all the sudden having to make adjustments to how you start your stove/having trouble getting the fire started.

 

[bsearcey]

Todd. I have two air controls. One on the ash door (below) and one on the side feed door. I hardly ever have the lower air open except when I'm starting a fire. Last year I did use it more because of my wood. This year with the hackberry it has not been necessary. Typically when loading after coals are established I just crack the side air just to get the new wood going, then shut it down.

certified106. That is pretty much what I thought about using that grate on the bottom instead of having the center fixed grate. Didn't make much sense it should cause my problems.

The draft thing could have been because temps were just above 60 outside with a low pressure system moving in last night. This could have caused the lagging startup I was noticing. Once things got going she burned great. I ended up loading 2 larger pieces of the hackbery and 1 big piece of the dead hickory at about 10:45. Those 3 pieces just about filled the stove. I was a little worried given the past issues with a full stove, but proceeded to try. Everything caught nicely with very little air (side inlet). By 11:15 the probe above the cat was reading 1400 and the cat showed no signs of fouling. When I woke up this morning around 6 the upstairs was 75 and down stairs was 80, but temps outside were still 60. I really shouldn't have burned last night, just wanted to see how things would go.

Temps are supposed to drop like a rock starting today. We'll see how she does tonight.

 

[basswidow]

Not sure. I just swept the liner two weekends ago, so brushed it off good while up there. It was caked with cresote (tar kind). I attributed that to the burning I did last year. I haven't checked it since.

So you swept the liner / flue and there was alot of cresote and tar. Is it possible that there is still a some sticky cresote in the liner? Just knocking off the loose stuff could still expose some cresote lining the flue which could be igniting and causing the jet noise (chimney fire)?

I'm not a sweep. I am a wood stove rookie, but what you have been experiencing would scare me and I would be concerned about the safety of the stove for my family. Certified Sweeps have a camera they can put up the flue and make an inspection. Just for piece of mind, I would take atvantage of this 60 degree weather and let the stove burn out and have a chimney inspection.

 

[bsearcey]

I've thought about that quit a bit, but by this point after having the same thing happen three times I'm pretty convinced it is not a chimney fire. Just to be clear the really tary stuff was on the underside of my chimney cap, not inside of my liner. What was inside the liner was predominantly a crumbly type buildup. Probably considered creosote, but definitely not the sitcky tar stuff. After I swept the chimney there was little if any residual tar left on the sides at the top of the pipe, which is where you would expect to find the greatest amount of deposit occuring. It was pretty much bare metal. Secondly, on each of the occasions there was absolutely no flame/sparks issuing from my chimney. Maybe I'm mistaken, but if it was a true chimney fire I would expect to see flames coming up. It just doesn't make sense that deposits would be occuring lower in the liner (where it is hottest). Please correct me if I'm wrong.

I do plan on getting back on the roof this weekend and taking a flash light to look down the liner. I didn't think to take one with me last time. Just to get a quick look.

Supposed to be in 29 tonight. Ridiculous weather we are having. I'm taking things easy with it. The only time I ever experienced the scary stuff was when the stove was stuffed full with the hackberry. I think for the time being I'll just keep my loads to half size and probably mix in some of my less seasoned wood, which is counter intuitive, but I'm still leaning towards the wood being the issue (sorry Dennis).

 

[bsearcey]

Found this picture on line. This is pretty much what my pipe looked like before sweeping, just not as think a layer.

 

[basswidow]

If you got it down to bare metal, then it shouldn't be the chimney.

Hope you get to the root of it.

 

[bsearcey]

Thanks me too.

 

[international5288]

Nonetheless, I absolutely can believe that your wood can be "too dry" because I have similar problems if I try to burn really dry wood, or wood that is very dry and not dense. My stove is different but the symptoms are the same. It took me a while to figure out the problem was the wood and not the stove. For instance if I try to burn elm that is standing dead and "dry as a popcorn fart," my stove goes insane. The wood gasses out too quickly and produces too much smoke, it is akin to feeding your cat a diet of acetylene and oxygen. It's like a blowtorch when it gets to the cat! Then when you try to calm things down by starving off the air, you get back puffing as the smoke mixture "explodes" in the stove when it finally does take a gulp of oxygen big enough to ignite things. (does your stove have an automatic air control? bet it does) It is a scary thing. It is really not much different than detonation in an engine. Instead of a normal burn you are getting an explosion when things start to go nuts. I think the solution to your problem could be very simple... mix something else in with the hackberry. I learned to mix my "super dry" wood at about a 1-4 ratio with "normal dry" wood and things hum along nicely. I also cut back the secondary air availability to the cat, effectively "richening" the mixture reaching the cat. Yes, I get a wisp of smoke out the stack, but no more china syndrome.

 

[bsearcey]

Woo hoo I'm not completely nuts, well I guess that's still up for debate. At least someone else has experienced this type of thing. Thanks international5288. My symptoms don't exactly match your description, but I think that is just due to different stoves. My stove isn't very "auto" anything and I don't have any air control for the cat. My stove was built in 83, and I think they were just figuring out the best way to incorporate them into stoves. I know the later models of my stove do have an air control for the cat. I have experienced mini explosions so to speak when I've opened a door or air inlet during these occasions. All the smoke and gases ignite immediatly in the box making a puff sound, but strong enough to rattle the stove a bit.

Yeah. Part of me wants to try and load the stove one more time with all hackberry just to see if it does it again, but I don't think I will. Three times is enough. If I do full loads I'll at least try a half and half mix with some of my denser and less seasoned wood. When I say less seasoned I'm talking b/t 20-25 MC.

You brought up a good point about the density of the wood. Hackberry is right at 21 BTU so not super dense like oak. I wonder if I had some oak at 16 MC would I have this kind of thing happen.

I really appreciate the confirmation on the wood. At least I know it's not something I've done wrong or that the stove itself is messed up. I'd rep you if I could.

 

[international5288]

If you are sure the stove is ok then playing with your wood mixture is certainly worth a shot. My description above wasn't the best, but just be assured sometimes it can be a problem with wood that gasses too fast. Some stoves can handle it, some can't. I went through a whole burning season frightened for my family's life until I figured that out, it was like my stove had an afterburner. And this may seem counter-intuitive, but try giving your stove a little more air when you call it a night. Keep some fire on the logs to burn off some of the smoke, don't let the cat have to handle it all. I wouldn't have believed that either if I hadn't fit some digital gauges to my stove, and using them I could plainly see that more air equated to a stove that didn't run away temperature-wise, and generally behaved itself much more steadily, with no puffing. It just sounds to me like your stove is out of balance for the wood you are trying to burn, not enough primary air and too much secondary air. So you have to change something. Throw some oak in there and report back.

 

[Rockey]

Heres my .02. Forget about the wood being too dry. Thats not your problem. My cat insert will sound like a jet engine if I open the bypass with a full load of dry wood in it. It should. With the bypass closed, if you are seeing backpuffing then your not drafting correctly through the cat. I'm betting this problem reared its head after you swept the chimney. The creosote you knocked loose is obstructing the flow somewhere. I dont know how your stove is designed but you need to look a little further into it. I know you said you pulled the cat and looked behind it but there is probably more you cant see. I know mine is hard to tell by just looking. Use a telescoping mirror or bend a hanger and try knocking around in there. Good luck and keep us posted.

 

[bsearcey]

Rockey. The first time it happened was before I swept the stove. It happened twice after I swept.

Trying to describe the inside of a stove is difficult, but I don't have to pull my cat to look behind it. I can see directly into my flue collar with the cat installed and I don't see any blockage leading from the flue collar to the T connector. My neighbor has a mini video scope. I'll borrow it and fish it in to see if, maybe there is a blockage that was there prior to sweeping that I didn't get when I swept. It's possible, although my SS liner is pretty much a straight shot from the T to the top, with a slight bend as it comes thorough the fireplace damper hole. The material I swept out took minimal effort to knock off (at least at the the top of the stack).

I agree that it seems like the draft (during the times when it's gone nuts) may not be pulling hard enough to pull the smoke quickly through the cat, thus causing buildup on the cat to the point where the cat can no longer keep up. However when the bypass is open the draft is fine.

Last night I did load the stove full. I used a half and half mixture of the 16MC hackberry, and an unknown MC red oak. The red oak was from a many year dead tree, and is checked good. If I had to guess I'd put it at 25MC. I should really check it though. Anyway, following my typically process I got everything going good. Engaged the cat with probe temps around 800. Approximately 30 mins later the cat was at 1600 glowing super hot and completely lit. When I lifted the cat cover plate you could here the air rushing up the into the flue. I had no issues last night.

I am beginning to wonder though about the distance of my cap from the top of my flue. Could this cause a draft problem by restricting the smoke from existing freely. This morning when I got the fire going I went outside to check the stack, and of course it was smokey because I had just put fresh wood on. However the smoke, as it rolled out from under the cat seemed very slow. My stack should have been decently warm because prior to loading it full of wood I had burned two splits with air open to the stove. I think this weekend I'll completely take the cap off and run the stove without it to see what happens.

 

[bsearcey]

Just a quick update.

I've burned several full loads since the last incident without a reoccurence. All that has changed is I am now mixing other wood (primarily red oak) in with the hackberry and installed the central fixed grate. I still haven't tried a full hackberry load. If it ain't broke don't fix it.

As a side note, I've been in discussions on another thread about the use of blowers and the cooling that occurs. I thought maybe that could be causing what was happening. Running the blower (even with cat engaged/lit at first could cause the cat to cool down to the point that it is no longer active before the wood has burned off. Thus causing the build up. I have been using the blower and watching the cat carefully since mixing the wood, I have not seen any instance where the cat appears to be affected during the entire burn cycle.

So...I guess I'll never know if it is the hackberry for sure (all though 3 times is a pretty good indicator). I just don't have it in me to load with all hackberry again to see if it happens.

Thanks for everybody's input.