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[Chas]

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?

[woodbutcher]

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.   

[Chas]

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.

[slimjim]

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.

[woodbutcher]

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.   

[slimjim]

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!

[woodbutcher]

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.     

[Chas]

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.

[MattyNH]

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..

[slimjim]

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?

[fryedaddy]

How often are we talking about flames?

If your talking about daily, I think that needs to be looked at!!

[Jwood]

I agree with slim.

[woodbutcher]

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.

[Chas]

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.

[slimjim]

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