Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: Chas on September 18, 2014, 07:51:34 AM
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Hey Slimjim, in the past week or so you have commented to a few people about the need for a barometric damper if they have too much draft. Are there any set guidlines on chimney height or other scenarios that would show the need for one? I have a 7 ft. chimney on my Ridgewood (to clear the carport roof), and quite often have flames coming out the top of it when the stoves draft damper is open. Could the flames indicate to much draft, thus pulling to much heat out of the chimney, or is this just a sign of a good hot fire?
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Putting a barometric damper on an outdoor wood boiler is a bad idea. If you live in a place where the winter is cold and snowy, it could freeze up and will cool your chimney down to where you have a creosote build up on the top of the chimney. If you are having fire shoot out of the top, when the boiler is running, that means that your blower is blowing the fire and heat up the chimney. Sounds like a bad design in the boiler. Putting a baffle inside the boiler in front of the chimney outlet a couple of inches from the outlet might help.
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The Ridgewood Stove doesn't have a blower, and there is a baffle before the chimney. A fellow coworker has a Central Boiler 5036 and quite frequently has flames coming from his chimney also. I don't think it's that uncommon.
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I will disagree with woodbutcher, A barometric damper will most certainly allow you, the home owner to reduce the draft, it will not freeze up as the stack temp when operating will thaw any frost, in fact a typical steel barometric damper will burn up and corrode in about 2 years, if you have somebody local who can cut you one then make your own.
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You might solve one problem with a barometric damper but you will cause another problem. The damper will cool the chimney pipe down when the boiler shuts down. This will cause creosote to build up in the pipe. You will be cleaning the chimney pipe every week or two. A cool chimney pipe is a magnet for creosote. If the flames you see are when the draft door is open and not when it is closed, it is unburned gasses igniting in the chimney. I still would not put a barometric damper on the boiler. First check with the company who made the boiler and see what they say. I don't know of any OWB company that recommends a barometric damper.
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If you must extend the stack then WE certainly recomend a barometric damper, FLAMES coming from a stack is not only a waste of fuel and added polution but also a major fire hazard, if your unit has a problem with creosote it might be a good idea to clean the chimney when it gets dirty, Perhaps that is the difference between a low budget boiler and a high end well designed unit!
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Any time the chimney temperature drops below 300 degrees you are going to have a creosote buildup.
I have 8' chimney on my CB and I had a small flame come out the top once. As soon as the natural draft door closed the flame went out. It was not a roaring blaze, just a small flame. It come for unburned gas going up the chimney. It depends on the wood and the moisture content of the wood. I've only seen this once. But if you are still want to put a damper on the stove, I would put on a manual draft inside the chimney. They are the old fashioned ones used by the old timers that burned wood for heat and for cooking. They are cheep and will last a lot longer than a barometric damper. A high end boiler can cause this problem just as well as a more inexpensive one. Top dollar for a boiler don't make if work better.
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I suppose the flames could be from unburned gasses in the chimney, I hadn't thought about that. Or is it possible that excessive draft is simply sucking the flames out the top. Same with mine, as soon as the natural draft door closses, the flame goes out. If it were to be excessive draft, are there other ways to control it besides using a barometric damper?..... such as not letting the natural draft door open as far?....maybe restricting the outlet on the chimney??? If it is unburned gasses, OK, but if it is too much draft I'm wasting wood and losing alot of heat out the top. By the way, there is no creosote in the chimney so it's not just a chimney fire.
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You know what guys..I have a 19 foot stack..I want the fire to come out of the stack.. It means I have a clean stack.. When I see the fire come out..It looks like a butane flame out of a lighter..
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Woodbutcher, Please allow me to explain something to you, You consistantly put down the value of the more expensive stoves, if what you are saying is true then please explain why my more expensive stove runs a stack temp at the breach of the unit , inside the stack of 260 degrees with no creosote and your inexpensive tank in a tank design runs over 1000 degrees with flames coming out of the stack. Don't get me wrong here because I have nothing against those conventional unit but I do take offense to your uneducated insinuations that our higher cost units are no better value than yours, Are you serious?
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How often are we talking about flames?
If your talking about daily, I think that needs to be looked at!!
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I agree with slim.
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Woodbutcher, Please allow me to explain something to you, You consistantly put down the value of the more expensive stoves, if what you are saying is true then please explain why my more expensive stove runs a stack temp at the breach of the unit , inside the stack of 260 degrees with no creosote and your inexpensive tank in a tank design runs over 1000 degrees with flames coming out of the stack. Don't get me wrong here because I have nothing against those conventional unit but I do take offense to your uneducated insinuations that our higher cost units are no better value than yours, Are you serious?
I never put down a more expensive boiler in favor a less expensive one. I have a Central Boiler and it's not a cheep model. What I'm saying is that a less expensive model will work just a good as a high priced one. Everybody's situation is different and you can't fix every problem the same way. I think most the less expensive boilers are built just as good as the high cost boilers. For and example you can get 2 plumbers together and they will each will have his own way of doing the plumbing for the same home.
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Wow! 12 posts on this topic and I still haven't got an answer to the original question. To much draft? Maybe unburned gases? Just a good hot fire? Any thoughts? Either way the stack is clean.
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Part of the problem of flames from the stack is an uncontrolled burn, the gasses are being created faster than the available air can be injected to the fire, another problem is that there is not enough heat exchanger to absorb that heat, excess draft simply draws that heat out of the stack before the stove can either burn the gasses or absorb the heat into the water, this is why the gassers do a much better job of efficiency than a tank in a tank, it is also the reason that a gasser requires better / more consistant fuel and the tank in a tank can burn stumps if you choose
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I do agree Slim, but maybe the problem could be solved with a cloverleaf chimney cap. As for your gassers,
everybody can't build a roof over there wood to keep it between 15-20% moisture. And at a 20% failure rate, gassers just aren't a good investment for the cost of one.
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Again woodbutcher, You seem to not be reading so good! Failure rates of about 20% were seen on the early models of the Wood Doctor gassers, They are belly up and I quit working with them when they buried their heads in the sand leaving many of my customers screwed, a lot has been learned over the past 5-6 years, Again you exagerate with moisture content of the wood, Gassers can burn greener wood as well but there is a learning curve, they simply need to have a decent load put on them when burning not so well seasoned wood and they also need to be kept clean, as any boiler, indoor, outdoor, gasser or non gasser, I burn very green oak at about 80% of my shows with absolutely no issues. Your idea of the clover leaf chimney cap is not a bad idea but it still does not solve the high stack temp issues of most conventional boilers, let me ask you a couple of questions, first, have you ever measured the exhaust temp(not the stack but actual exhaust temp )of your CB when it is running hard, I have measured several of them and will not post those temps here simply because I don't bash other peoples product. Second question, have you ever seen our B-L series units, they are very competitive in price to what you are currently running, burn much cleaner and BOAST an exhaust temp of 550 degrees F, sometimes price does reflect quality and design!
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Let's get back to the original question. CB does have a solution for lowering the burn rate, which might help to solve the problem that Chas has.
Page 18 Central Boiler Parts catalog, can be downloaded through CB web site at
Under Classic Outdoor Wood Furnace Brochure
Classic Outdoor Wood Furnace BrochureClassic Outdoor Wood Furnace Brochurehttp://www.centralboiler.com/
Chimney Tee Restrictor Kit
Installed in chimney tee to lower the burn rate.
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OK so let's recap shall we, You say that the increased draft and flame out of the stack is not an issue, I think it is. You say there is not enough difference betwwen high cost boilers and low cost boilers to make the high end stuff worthwhile, I think the fact that they even sell the restrictor plate is evidence enough that a true 3 pass boiler and exhaust temps of 550 degrees or less without a restrictor plate is evidence enough that you are quite bias to your product, I have asked you several times if you have ever seen our product , you have never answered, you might want to have a look at it before you comment on another companies products and current pricing, by the way the B-L 28-40 is now listed for $8300 34-44 is $9700, if you ever saw the difference between a normal conventional unit and the B-L series in operation you probably would not be making the comments that you have in the past regarding value
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You're right. I have never seen a P&M anyplace close to to me. I wish I could see one in operation.
I didn't come up with this solution, CB did. And I was bias about my CB. That was the old model. I don't think I would by the new model 6048 which runs over $9,000.,and the gassers over $12,000. Owner of P&M boilers are just no ware to be found in my area.
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That might have something to do with people looking at prices before seeing the quality and design!
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Where are you located Woodbutcher?
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Where are you located Woodbutcher?
South Central WI. About 50 miles north of Milwaukee.
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Woodbutcher, I am not a dealer just a happy owner of a BL 2840. Give P&M a call and inquire about a dealer close to you so you can have a look. They might even put you in contact with someone in your area with one to talk to. I have been contacted a least a half dozen times and am always glad to show people my set up.
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Thanks Crow, great suggestion, seeing is believing !!
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I needed to add 8 ft of chimney on my bl 2840 in order to clear my peak. As per slim's recommendation I installed a damper in the breach. It should hopefully work fine there. She's not fired up yet so can't say yet how it will perform
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WELL DONE, Thank you!
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Darn upside down pictures. Lol
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Where did you get the damper?
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At my local plumbing/electrical shop. They do a lot of heating work as well so they happen to have some in stock