# Damper vs air control?



## greengiant (Feb 22, 2011)

Which works better in your opinion? Maybe too many variables??
A damper on the outlet/exhaust or an air control to control how much air enters the firebox? 

I feel like too much of my heat is going up the flue, so I've been messing with the air control a lot.


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## pook (Feb 22, 2011)

greengiant said:


> Which works better in your opinion? Maybe too many variables??
> A damper on the outlet/exhaust or an air control to control how much air enters the firebox?
> 
> I feel like too much of my heat is going up the flue, so I've been messing with the air control a lot.


If "works better" means u want more heat, flue damper near the stove creates a turbulation zone & gives off more heat from the fluepipe.


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## Mike PA (Feb 22, 2011)

I am using both a baro damper and air control. I am not sure I've gotten the feel for it all just yet, as I am new to using a baro damper. What I like about the baro is the ability to dampen the effect of windy days. The damper was really swingin the other day when it was so windy here. I did not realize before just how much it would open and close as a result of the wind. I like the air control to further close or open the stove, depending on my heat demand. A baro set at the correct level should basically regulate the air flow into your stove as a result of drafts, making the air control valve less important. My unit has a forced draft, so cutting the air back cuts the amount of air forced into the unit when the blower runs.

I am a little concerned about the baro damper in that it lowers the temperature of the flue gas because it brings in cooler air. I am concerned about the potential for more creosote build-up. I have not noticed a problem yet, so my concerns may be unfounded... We'll see what happens as the temps get warmer.


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## Highbeam (Feb 22, 2011)

Intake air damper for sure. Neither will get you more heat from an undersized stove so we are really talking about control here and since you are trying to control heat from the fire, the intake air will control how hot the fire burns.

Flue dampers are used to correct flue problems. Usually too much draft due to too much chimney. Too much chimney will suck the heat right out of the stove. If you have this issue then I would recommend a key damper. Installing a baro damper on a woodstove is not recommended for several reasons including the fact that when a chimney fire starts the baro damper will open up wide to pour oxygen and fan those flames into a blast furnace.

There is a reason that modern stoves aren't supposed to be equipped with flue dampers unless the chimney drafts too hard. Think 30 feet of double wall. Read the manual, it's right in there.


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## greengiant (Feb 22, 2011)

Highbeam said:


> Intake air damper for sure. Neither will get you more heat from an undersized stove so we are really talking about control here and since you are trying to control heat from the fire, the intake air will control how hot the fire burns.
> 
> .


 
This is what I've been doing this year since I seem to have fires getting too hot. I am hoping that by pulling out that air control to 'slow' down the fire, that I'm getting more heat into the house than up the chimney (via the blowers on the insert). In the long run, I would hope this means I use less wood too.


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## pook (Feb 22, 2011)

cooling the fluepipe slows the fire , most effective means is a heat reclaimer [Vogelzang} or a Magic Heat- similar. Chimney should be monitored for possible enhanced creosote.
Cooling the flugas results in a higher pressure in the firebox which forces more heat out the exterior of the firebox. = your best bet for heat gain as long as the chimni is clean.


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## Whitespider (Feb 22, 2011)

There will never be a stove in my house without a flue damper... period.

Y'all can believe what you want about the "new" stoves, but a flue damper should be installed on every one of them if you want maximum control and the best heat output, especially with low fires. A flue damper stops the heat from escaping out the flue... an intake damper can only arrest the flow of air from entering the stove, it can't arrest the flow of heat out.

The reason the "new" EPA stoves recommend not using a flue damper is because of emissions, it has nothing to do with efficiency... I don't care what the manufacturers, salesman and EPA have told you.

A Barometric damper does not stop heat from flowing out, it controls overall draft by allowing cold air to enter the flue. A Baro damper has no business on a wood burning stove because it cools the flue gasses, increasing the possibility of creosote build up. A flue damper, and learning to use it properly, is a far better choice. Baro dampers belong on oil burning furnaces only.

Don't forget that as wood burns the chemical reaction creates huge amounts of hot gasses... the amount of gasses exiting the stove far exceeds gasses entering the stove. An intake damper is worthless at controlling the escape of heat. A flue damper arrests the flow of those gasses, trapping the heat and creating a high(er) pressure in the stove, which does an excellent job of controlling intake air all by itself... I almost never touch my intake damper.


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## Cerran (Feb 22, 2011)

Actually on a modern EPA stove an outlet damper will not create greater efficiency either, and in many cases with shorter chimneys it will cause more problems.

Unless you have over-drafting problems it's always better to run without a damper. This allows for lower pressure drop and less flow disturbance on the gasses which will limit creosote buildup in the pipe.


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## Whitespider (Feb 22, 2011)

Cerran said:


> Actually on a modern EPA stove an outlet damper will not create greater efficiency either, and in many cases with shorter chimneys it will cause more problems.
> 
> Unless you have over-drafting problems it's always better to run without a damper. This allows for lower pressure drop and less flow disturbance on the gasses which will limit creosote buildup in the pipe.


 
Sorry, but I have to call BS on that... and I repeat...

Don't forget that as wood burns the chemical reaction creates huge amounts of hot gasses... the amount of gasses exiting the stove far exceeds gasses entering the stove. An intake damper is worthless at controlling the escape of heat. A flue damper arrests the flow of those gasses, trapping the heat and creating a high(er) pressure in the stove, which does an excellent job of controlling intake air all by itself... I almost never touch my intake damper.


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## Wood Doctor (Feb 22, 2011)

Whitespider said:


> Sorry, but I have to call BS on that... and I repeat...
> 
> Don't forget that as wood burns the chemical reaction creates huge amounts of hot gasses... the amount of gasses exiting the stove far exceeds gasses entering the stove. An intake damper is worthless at controlling the escape of heat. A flue damper arrests the flow of those gasses, trapping the heat and creating a high(er) pressure in the stove, which does an excellent job of controlling intake air all by itself... I almost never touch my intake damper.


+1. That's exactly why the Federal Airtight stoves work so well. The block off control to the direct combustion fire box serves as a damper and allows the secondary combustion chamber to work, heating the flue gases to as much as 1400 F before they enter the chimney. 

Thus, practically no wasted smoke enters the chimney and enormous heat is captured inside the building that is being heated by the stove. In addition, the Federal Airtight stoves allow control of the intake air to the main firebox as well.


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## ks_osage_orange (Feb 22, 2011)

I think I may have to side with Whitespider on this one. I have only owned 1 EPA wood stove I believe it was a Lopi Patriot. (Don't quote me on the model name, but it was a Lopi) I installed it without a flu damper and the 4 years I burned it I always wished I had one installed. The stoves I had before and since that one I have had flu dampers and found when the flu was wide open like when first starting a fire or adding wood, the flu itself would rise in temp rapidly this tells me a lot of heat (not just talking about gases here, but heat energy) was making its way up and out of the chimney. Then when I shut the damper down the flu decreases temp, but the stove increases its temperature putting more heat where I wanted it. My bet is that being able to control both air intake and outflow would be the best way to maximize efficiency and heat transfer on most stoves. Once you have learned the ins and outs of your particular set up.


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## Cerran (Feb 23, 2011)

Whitespider said:


> Sorry, but I have to call BS on that... and I repeat...
> 
> Don't forget that as wood burns the chemical reaction creates huge amounts of hot gasses... the amount of gasses exiting the stove far exceeds gasses entering the stove. An intake damper is worthless at controlling the escape of heat. A flue damper arrests the flow of those gasses, trapping the heat and creating a high(er) pressure in the stove, which does an excellent job of controlling intake air all by itself... I almost never touch my intake damper.


 
What it in effect will do is limit the flow, lower velocity and will in fact make combustion in the stove less efficient. The higher pressure in the stove can actually slow down oxidation and change the flow patterns inside the stove preventing proper operation.

Also a outlet damper may raise the inside stove temperature which could in fact cause more heat to be lost out of the chimney. A lower flue temperature at the same flow will always result in an efficiency gain.

It's the same concept as an inlet damper and an outlet damper on a fan. Inlet dampers by their nature are always more efficient and offer better control over a wider range. The same principle applies here.

What really matters is operating the stove in the right temperature range to burn off all of the gasses.


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