I have alot of issues with backpuffing. I have an Dutchwest extra large catalytic stove. I was burning tonight and it is about 25 degrees outside so I decided to engage the combustor ( I have to wait till it gets that cold due to draft issues) Anyhow, I was wondering if some of my backpuffing issues are made worse by the size of the wood I burn. I split things real small, about 2 inches by 2 or 3 inches. I may throw five or 6 pieces in along side a good size split and let it heat up and then turn it down in stages. When I get it turned down the to about 1 turn I get a good backpuffing. I was wondering if the small pieces are making it worse by creating to much surface area and to many unburnt gasses. Please chime in and let me know what you think. I will try working with some bigger pieces / splits tomorrow and see what happens. I am about ready to give up on the wood burning. I have been trying for over 2 years and I constantly have problems trying to slow burn. I have a 20-23 foot 11x7 clay liner encased in stone running out side the house.
Theory about my backpuffing issues
- Thread starter lillyrat
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Brian VT
Minister of Fire
I get back puffing when the wind is just right and moving down a cold flue. When my flue is hot I don't have the problems.
Matt
Matt
I think Brian has it right. Put in an insulated liner and I think the stove will behave much better.
I could turn up the air but I want to sleep sometime during the night. What kind of money am I looking at for an insulated liner? The stove has been here for 15-20 years but I have only been burning it for 2.
jpl1nh
Minister of Fire
I too think the real solution is a chimney liner as others have said but I also think you are probably correct about the smaller splits. I have similar issues for the same chimney reasons you have. For long burns I use bigger splits packed tight on a hot bed of coals. I burn it wide open for 5-10 minutes, then turn down in 2 or 3 stages to the overnight burn setting. If I go a bit to far, for a bout a half hour stage about 15-20% into the load burn, I'll get back puffing. Playaing around with the air settings has helped me find where I'm ok and where I'm not. You may also find you can cut your air back even a little bit further than what you have been which cuts the oxygen supply so low that the combustor is doing almost all the work and you'll have less back puffing but even so you'll probably hit a point in the burn where you go through a bit of a back puff stage.
webbie
Seasoned Moderator
OK, this is where a little experience comes in. I have heard of that exact same problem a few times...with that exact model stove!
This assumes that the backpuffing is a result of delayed catalytic ignition of gases, causing a positive pressure inside the stove to spew out smoke...for a second or two.
A possible inexpensive solution...if the problem is as I outlined and not a general chimney problem...is a barometric damper on the stove pipe between the stove and the chimney. This can even out the draft and eliminate the imbalance.
Might be a slightly long shot, but who knows? Fact is, as i said, I remember dealing with that problem...with that stove....back in the 90's, and also hearing about it here. It is probably a sort of design flaw or just a "personality".....either of which can probably be fixed one way or the other.
This assumes that the backpuffing is a result of delayed catalytic ignition of gases, causing a positive pressure inside the stove to spew out smoke...for a second or two.
A possible inexpensive solution...if the problem is as I outlined and not a general chimney problem...is a barometric damper on the stove pipe between the stove and the chimney. This can even out the draft and eliminate the imbalance.
Might be a slightly long shot, but who knows? Fact is, as i said, I remember dealing with that problem...with that stove....back in the 90's, and also hearing about it here. It is probably a sort of design flaw or just a "personality".....either of which can probably be fixed one way or the other.
Backwoods Savage
Minister of Fire
lillyrat said:
You've gotten good answers to the chimney problem so I'll chime in on the wood.
No, larger pieces will not help and may make it worse.
I can understand why you are about ready to give up, but have faith. Many people have problems, but they can usually be fixed. However, it might take a few dollars, but it should be worth it in the end.
Thanks for all the reply's. Would switching to a more modern stove help? I am guessing that the chimney issue is going to need addressed regardless of getting a new stove or sticking with this one. Savage, what is your reason for thinking that bigger splits won't help, just curious, I like to know the theory behind stuff or if it is just from experience. I respect your post, I just like to know the why's of everything.
Thanks for all the replies.
Thanks for all the replies.
Backwoods Savage
Minister of Fire
lillyrat, if indeed this is a chimney problem then it would not matter which stove you had.
The theory is that with smaller splits, you will get a hotter fire, therefore improving the draft but larger splits will tend to burn slower, therefore reducing the draft. Or to put it a different way, look at how you start a fire in a cold stove. You first start with very small kindling, which lights much easier than the large stuff and burns up quickly. You could have a total fire with nothing but kindling or wood chips. You would get a hot fire going fast. But with the larger splits you simply will not get that hot fast fire. In addition to that, if you look at the total surface of the wood which is exposed to fire, you will have much more exposed surface with say, 2" x 3" pieces versus a 4" x 6" piece, thereby giving you a hotter fire. Hope this makes sense.
The theory is that with smaller splits, you will get a hotter fire, therefore improving the draft but larger splits will tend to burn slower, therefore reducing the draft. Or to put it a different way, look at how you start a fire in a cold stove. You first start with very small kindling, which lights much easier than the large stuff and burns up quickly. You could have a total fire with nothing but kindling or wood chips. You would get a hot fire going fast. But with the larger splits you simply will not get that hot fast fire. In addition to that, if you look at the total surface of the wood which is exposed to fire, you will have much more exposed surface with say, 2" x 3" pieces versus a 4" x 6" piece, thereby giving you a hotter fire. Hope this makes sense.
Thanks for the reply and explanation yes it makes sense. I got you on the smaller pieces and more surface area = hotter fire. My thought was that since I am slow burning, that it would be better to have less surface area and less outgassing at the lower temps which would give me less gasses which from what I understand cause the backpuffing.
Backwoods Savage
Minister of Fire
lillyrat, also remember that backpuffing can be caused from too slow of a burn when the smoke going up the chimney gets cooled too much and suddenly just sits there. I've seen some stoves puff to where you really hear it and suddenly there is a big flame in the stove and then it operates great. It was just the gasses igniting and the mini-explosion shoves the smoke up and out the chimney and then all is well for a while. When that happens, you almost always will smell smoke in the house big time.
PunKid8888
Feeling the Heat
I wrote a response last night but I guess I never hit the reply part.
I thinking your extremely large cold chimney is the culprit. Most likely you have a 6dia flue on the stove (28in^2) your now dumping that into a 11x7 (77in^2) basically increasing the cross section area 3 fold. So when ever you increase cross sectional area you loose velocity, or your case draft. now you are trying to damper down your stove, which is reducing the speed of the gasses in the 6inch pipe, and the result is almost nothing for flow out the chimney. A little gust of wind can then over power your draft causing the back puffing.
That's my theory, so I would address the chimney with some sort of liner and get the cross sectional area closer to the manufacture recommendation.
I thinking your extremely large cold chimney is the culprit. Most likely you have a 6dia flue on the stove (28in^2) your now dumping that into a 11x7 (77in^2) basically increasing the cross section area 3 fold. So when ever you increase cross sectional area you loose velocity, or your case draft. now you are trying to damper down your stove, which is reducing the speed of the gasses in the 6inch pipe, and the result is almost nothing for flow out the chimney. A little gust of wind can then over power your draft causing the back puffing.
That's my theory, so I would address the chimney with some sort of liner and get the cross sectional area closer to the manufacture recommendation.
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