I was out snooping in my neighbors backyard...
- Thread starter the GOAT
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stihly dan
Addicted to ArboristSite
That was my 1st successful link ever. Yaeh for me. 
1 stihl nut
former space alien
That would be a blue ribbon...
That is correct. But no matter if it's a flower or a ribbon, the goat is gonna eat it.
Fubar
treehugger
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you should quickly report him to the wood Nazi police , i think they are over on that other forum what was the name ? oh well , cause we can't have blatant wood abuse like this going on , cause before long everyone will start thinking there is no wrong way to stack wood .
ppkgmsy
ArboristSite Operative
I don't understand. My neighbor was just quoting from the owners manual so he doesn't know. The stove has a single inlet control above the ash drawer. Wouldn't this just control air draw? Regardless of how it's set, wouldn't a damper on the pipe keep heat from passing out of the house? Even on a sealed stove, wouldn't a damper be beneficial? I'm not trying to be argumentative, I honestly don't understand.
Yes... usually... depends... sort'a...
Even on the most modern new-fangled stove the volume of gas exiting the flue pipe will be greater than air entering the firebox. During combustion the wood is being converted into gas and heat energy... and the gas is hot, meaning it is expanded to a larger volume than room temperature gas of the same makeup. A flue damper will also allow you to adjust the strength of draft acting on the firebox. The combustion air inlet adjustment can't do that, it can only restrict total flow and then only to a point... the harder the chimney is sucking, the more air will flow into he firebox at any given inlet setting.
Don't let anyone tell you a flue damper is not needed... because it depends on the characteristics of the installation.
And don't let anyone tell you a flue damper won't make any difference... because it will give you more control in any installation.
And yes, a flue damper can or may reduce the heat exiting the flue (depending)... even on the most modern, new-fangled stove.
Personally I wouldn't install any wood burning appliance without a flue damper... I figure it's better to have it if ya' need it, than it is need it and not have it... and I've needed it in every installation.
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brenndatomu
Hey you woodchucks, quit chucking my wood!
Agreed. True dat ^ ^ ^
Chris-PA
Where the Wild Things Are
I should not have been snarky and I apologize.
The flue works by the pressure difference between the top and the bottom, and that in turn is driven by the temperature difference between the top and bottom. A damper in the stove pipe is simply a flow restriction, and if there is air flow it creates a pressure drop - so the stove sees a higher pressure on it's outlet and the flow is reduced. A flue damper does nothing unless it is limiting the rate of flow. The static pressure differential is still the same from top to bottom of the stack.
A restriction on the air entering the stove creates a pressure drop there instead. What matters is the pressure differential between the stove inlet and the stove outlet, which determines the rate of flow through the firebox and the rate of combustion. If the stove is sealed it mostly doesn't make any difference which way you do it. One thing about using a flue damper on the outlet is that you are putting the pressure drop on the outlet and moving the firebox closer to the air pressure in your living space - if the conditions change and you end up with a smaller pressure difference between the top and the bottom of the stack, you could end up with smoke in the room.
The goal of all these dampers is to limit the air flow into the stove and thereby to limit the rate of combustion - you can do that by limiting the flow anywhere in the path. The thermal expansion of the gases in the stove is irrelevant as it only changes the size of the openings required.
If you have a stove that is not sealed, or a secondary combustion stove where the secondary air cannot be limited, and flue with a strong draw, a damper might be a good idea as a safety in case you need to stop it down.
.404
The Ramster
I've got a good goat story. Who would like to hear?
1 stihl nut
former space alien
Maybe later.
I've got one about sheep.
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.404
The Ramster
I had multiflower rose in the hollers. All the rest of the pasture was clear but in the crevices that stuff was proliferous. Uncle Butch says, "Come on over boy, I got an old goat you can have give him to ya. They'll eat anything. Put old 'Billy" in the ravine with a tub of water and he'll live on that multiflower rose till you tell him different." Now Billy was young enough to still be considered twopeckered but old enough to only have one horn left. I took it back to the farm. Tied him up with some water and found it to be true by the next morning that he would eat anything including his rope, the tire valves off the 2030 John Deere, the seat on my Yamaha YZ 465, my brother's electrician pouch screwdriver handles included, nine bags of cattle supplement and the mixed feed that I found him standing in the bin of eating and crapping his way to a death warrant.
A busted goat is a dangerous one. When I confronted him, he took the storm door off the barn on his way to bust the insulators off enough one wire electric fence to let out 60 voracious ralgro-enhanced feeder calves into my truck garden. When I did the old trick you do to your brother chasing him around the house one direction, then switching him up to tackle him coming around the corner at speed, I got him by the horn and rear legs. Then Dad rolled in just in time to see me in a hard to explain position getting my hooks in from a clean side mount on a 10 year old goat.
A busted goat is a dangerous one. When I confronted him, he took the storm door off the barn on his way to bust the insulators off enough one wire electric fence to let out 60 voracious ralgro-enhanced feeder calves into my truck garden. When I did the old trick you do to your brother chasing him around the house one direction, then switching him up to tackle him coming around the corner at speed, I got him by the horn and rear legs. Then Dad rolled in just in time to see me in a hard to explain position getting my hooks in from a clean side mount on a 10 year old goat.
ppkgmsy
ArboristSite Operative
Good stuff, Chris, thanks. Great explanation. One more question. You write:
"The goal of all these dampers is to limit the air flow into the stove and thereby to limit the rate of combustion - you can do that by limiting the flow anywhere in the path. The thermal expansion of the gases in the stove is irrelevant as it only changes the size of the openings required."
If one opens the stove inlet and closes a pipe damper, wouldn't that increase rate of combustion? Also, wouldn't that increase expansion of the gases because there would be maximum combustion trapped in the most limited space? Again, I'm truly not be argumentative, I appreciate being educated here.
"The goal of all these dampers is to limit the air flow into the stove and thereby to limit the rate of combustion - you can do that by limiting the flow anywhere in the path. The thermal expansion of the gases in the stove is irrelevant as it only changes the size of the openings required."
If one opens the stove inlet and closes a pipe damper, wouldn't that increase rate of combustion? Also, wouldn't that increase expansion of the gases because there would be maximum combustion trapped in the most limited space? Again, I'm truly not be argumentative, I appreciate being educated here.
Chris-PA
Where the Wild Things Are
We control the combustion by limiting rate of air (oxygen) flow into the firebox. Unless you get to the point where combustion gases are coming out into the room, then it is still a flow through the inlet and into the firebox, and then out and up the flue. If the damper is restricting the flow by increasing the pressure at the outlet, then it is preventing more fresh air from being drawn in.
It's a closed system. The air has to go in the inlet and out the flue. The highest pressure is in the room at the bottom, and the lowest is at the top of the flue. If you put too much of a restriction on the outlet and the flow raises the outlet pressure too much, then the firebox moves closer to room pressure and you get smoke in the room. That really can't happen with an inlet damper - but if you cannot fully limit the inlet air then you could end up not being able to control the flow of air into the firebox, and not being able to limit the burn rate.
It's really pretty analogous to an electrical circuit with a battery, a wire and some resistors.
This is also related to the age-old rule for a fireplace that says the area of the flue must be at least 10% of the area of the fireplace opening. This is so that the flue can draw air into the fireplace at a high enough rate that there is a slight drop in pressure inside the fireplace relative to the room. If the fireplace were not at a lower pressure compared to the room, there would be no reason for the smoke to stay in there, and it would just wander out into the room.
Static pressure differentials, flow restrictions, closed systems, battery circuits, ya-da, ya-da, ya-da...
Just because something works a certain way on paper don't mean it will work that way in actual practice... and that's been proven time 'n' time again.
Tell ya' what ya' do.
Just because something works a certain way on paper don't mean it will work that way in actual practice... and that's been proven time 'n' time again.
Tell ya' what ya' do.
- Get a good fire goin' in your stove, then slowly start closin' the air inlet and watch how the fire reacts.
- Do the same thing with the flue damper and watch how the fire reacts.
- Get the fire goin' good again, leave the flue damper open and close the air inlet to minimum for ½ an hour... measure the temperature of the stove top and sides.
- Do the same thing but leave the air inlet open and close the flue damper to minimum for ½ an hour... measure the temperature of the stove top and sides.
- Try it with the flue damper open ¾ and the air inlet closed ¾... measure the temperature of the stove top and sides.
- Again with the flue damper closed ¾ and the air inlet open ¾... measure the temperature of the stove top and sides.
- Come back and tell me, with a straight face, they do the same exact thing and it don't make any difference which one you use to adjust the stove.
LOL @ your new signature. FYI I figured it out without actually clicking it so I'm not a moron.
You should click on it... I'm bettin' it's not what you think.Similar threads
