Chimney Damper

[TJ-Bill]

Since my Stove is out for another couple of days I was playing around with the idea of adding a damper to the chimney. I have a fairly new stove but I've never really been happy with the way it works. I find with the damper on the stove closed I still get to much air and on those really cold days I end up with a huge beds of red coals.

Would a 2nd damper in the chimney help?

 

[cnice_37]

I can't see how it wouldn't.... worst case is you leave it wide open.

Side note, check this out... SmartStove Integration #2 on Englander 13 NC

 

[TJ-Bill]

I just picked one up.. For 9$ you can't go wrong

 

[trophyhunter]

Since my Stove is out for another couple of days I was playing around with the idea of adding a damper to the chimney. I have a fairly new stove but I've never really been happy with the way it works. I find with the damper on the stove closed I still get to much air and on those really cold days I end up with a huge beds of red coals.

Would a 2nd damper in the chimney help?

Probably going to make it much worse, is that a catalytic stove or secondary reburn system? That's a very typical complaint from owners of secondary air system stoves that are using good aged dry hardwood that gasses off quickly with minimal air volume moving past it.

With the primary closed off there's still plenty of air from the secondaries to burn all the intial gas and not enough volume of air entering the firebox to avoid heavy coaling of the wood after it gasses off. Alot of fuel and heat is lost this way with EPA stoves, they need enough air supply to work as designed. Don't sweat the higher operating temperatures they run at, these things are at their level best running well to the hot side consistently.

They won't work like an old smoke dragon cruising along forever @300* and flue dampers will make a perceived problem worse. Let some air move through these new EPA stoves, choking them off is the source of most complaints.

 

[Ayatollah]

Probably going to make it much worse, is that a catalytic stove or secondary reburn system? That's a very typical complaint from owners of secondary air system stoves that are using good aged dry hardwood that gasses off quickly with minimal air volume moving past it.

With the primary closed off there's still plenty of air from the secondaries to burn all the intial gas and not enough volume of air entering the firebox to avoid heavy coaling of the wood after it gasses off. Alot of fuel and heat is lost this way with EPA stoves, they need enough air supply to work as designed. Don't sweat the higher operating temperatures they run at, these things are at their level best running well to the hot side consistently.

They won't work like an old smoke dragon cruising along forever @300* and flue dampers will make a perceived problem worse. Let some air move through these new EPA stoves, choking them off is the source of most complaints.

That sounds pretty accurate in most cases, however a damper might help slow the draw in a long, high chimney application, where the rising heat gains momentum before it escapes the confinement of the chimney. The problem with the additional flue ends up being one of micromanagement. Closing the damper down when it's all coaled up might help hold heat and slow draw, but you have to be there to do it. Closing it down while your flame is aspiring could be downright unsafe, or in the least, cause you some smoke grief. I've also noticed that some woods work differently than others when you're managing a damper.

 

[Jredsjeep]

I can't see how it wouldn't.... worst case is you leave it wide open.

Side note, check this out... SmartStove Integration #2 on Englander 13 NC

thats neat, i have the englander 30, just a larger version. i wonder how it worked? i didnt see any feedback.

 

[Whitespider]

I have a fairly new stove but I've never really been happy with the way it works. I find with the damper on the stove closed I still get to much air and on those really cold days I end up with a huge beds of red coals.
Would a 2nd damper in the chimney help?

Nope, won't help... been there, tried that, doing that. I'm betting your EPA stove burns directly on the firebrick floor so no air can get under the fire (i.e. no grate), has a glass door and secondary burn... meaning near all air comes into the firebox from the top side (door air wash and secondary tubes/baffles). Most of the air for the fire comes in the door air wash, flows down along the door, flows across the top of the fire, and heats and rises before it ever gets to the back of the firebox. Then, to compound the issue, as the coals ash-over it insulates them from what little air there is. Eventually you end up with a deep bed of coals that can not produce a lot of heat because only the top layer is burning hot (until they ash-over), and the deep coals reduce the capacity of the firebox to the point you can’t get any more wood in it. The end result is you freeze your butt off.

The “design” works just fine when temperature are in the 40’s and 50’s, works OK (not great) when temps run mid 20’s to upper 30’s, ain’t work dog squat when it gets cold out… and dog squat will keep you warmer when temps go single digits or lower. I’ve said/asked this before… what good is 85% efficiency if it takes 36 hours to convert the fuel load into radiated heat? When it’s cold out you need a continuous high heat output… efficiency be damned! I have owned my first, and my last, firebox that does not burn on some sort of grate system with some sort of air intake coming in below it. That is the only possible way to make efficient use of the coal bed… That is the only possible way to keep it screaming hot… Air has to get under it.

OK, with that said (again), I can give you some tips that will help… I said help, but it won’t eliminate the problem. First of all, you’re gonna’ haf’ta babysit the firebox, which is a huge pain-in-the-azz. Keep as much ash cleaned out as you can so some air can get in between the coals. Once the fire collapses into a coal bed open the draft more and pull the coals to the front of the firebox (where the air can get to them). Every hour or so, stir the fire so ash falls between the coals to the firebox floor, and rake the coals to the front on top of the ash… as the coal bed burns down you might haf’ta do this every half hour, even every 15 minutes (yeah, I know, a huge PITA). When it’s really cold out, after raking the coals, place two, maybe three smaller splits on top, just enough to keep the secondary going continuously (more heat)… but even this will eventually fill the firebox with coals because much of the available air is used to burn the splits rather than the coals. Of course, if you’re gone at work all day, or prefer to get 8 solid hours of sleep… you’re just flat screwed.

It-is-what-it-is… the EPA fireboxes must pass emissions first, heat second. The efficiency rating is based on how much heat is lost through the flue… it has absolutely nothing to do with how efficiently they heat your home. What’s gonna’ keep you warmer from 25 pounds of firewood? An 85% efficiency over 18 hours to completely consume the fuel load, or 60% efficiency over 6 hours to completely consume the fuel load? Less wood/more heat is deception without actually lying… I base efficiency on how warm I am, not by what’s exiting the flue.

 

[Ayatollah]

Nope, won't help... been there, tried that, doing that. I'm betting your EPA stove burns directly on the firebrick floor so no air can get under the fire (i.e. no grate), has a glass door and secondary burn... meaning near all air comes into the firebox from the top side (door air wash and secondary tubes/baffles). Most of the air for the fire comes in the door air wash, flows down along the door, flows across the top of the fire, and heats and rises before it ever gets to the back of the firebox. Then, to compound the issue, as the coals ash-over it insulates them from what little air there is. Eventually you end up with a deep bed of coals that can not produce a lot of heat because only the top layer is burning hot (until they ash-over), and the deep coals reduce the capacity of the firebox to the point you can’t get any more wood in it. The end result is you freeze your butt off.

The “design” works just fine when temperature are in the 40’s and 50’s, works OK (not great) when temps run mid 20’s to upper 30’s, ain’t work dog squat when it gets cold out… and dog squat will keep you warmer when temps go single digits or lower. I’ve said/asked this before… what good is 85% efficiency if it takes 36 hours to convert the fuel load into radiated heat? When it’s cold out you need a continuous high heat output… efficiency be damned! I have owned my first, and my last, firebox that does not burn on some sort of grate system with some sort of air intake coming in below it. That is the only possible way to make efficient use of the coal bed… That is the only possible way to keep it screaming hot… Air has to get under it.

OK, with that said (again), I can give you some tips that will help… I said help, but it won’t eliminate the problem. First of all, you’re gonna’ haf’ta babysit the firebox, which is a huge pain-in-the-azz. Keep as much ash cleaned out as you can so some air can get in between the coals. Once the fire collapses into a coal bed open the draft more and pull the coals to the front of the firebox (where the air can get to them). Every hour or so, stir the fire so ash falls between the coals to the firebox floor, and rake the coals to the front on top of the ash… as the coal bed burns down you might haf’ta do this every half hour, even every 15 minutes (yeah, I know, a huge PITA). When it’s really cold out, after raking the coals, place two, maybe three smaller splits on top, just enough to keep the secondary going continuously (more heat)… but even this will eventually fill the firebox with coals because much of the available air is used to burn the splits rather than the coals. Of course, if you’re gone at work all day, or prefer to get 8 solid hours of sleep… you’re just flat screwed.

It-is-what-it-is… the EPA fireboxes must pass emissions first, heat second. The efficiency rating is based on how much heat is lost through the flue… it has absolutely nothing to do with how efficiently they heat your home. What’s gonna’ keep you warmer from 25 pounds of firewood? An 85% efficiency over 18 hours to completely consume the fuel load, or 60% efficiency over 6 hours to completely consume the fuel load? Less wood/more heat is deception without actually lying… I base efficiency on how warm I am, not by what’s exiting the flue.

Ha! Maybe the main goal of the EPA approved stoves is to get people fed up with performance, and change to electric and natural gas

 

[gregfox]

I'm going against the grain here. I have a stove with the secondary burn. I almost never shut down my intake and use the flue damper once the fire is going. If I shut down intake I'll end up with a bunch of unburned charchoal. I fought the intake and didn't use the damper for almost a year before an old timer straightened me out. Ever since then I've had much better luck. Coal management is part of the stove, I let the coals go down to where there are only enough to easily light the next load of wood. My stove only goes out every two weeks to clean out the ash...that is with oak, more often with hickory.

 

[trophyhunter]

Spidey nails it again, the EPA wood stoves are labratory compliant sock puppets designed to pass testing criteria and you have to babysit them constantly. They just are what they are, you have to burn them very hot with enough air moving over the top of the wood to create a wanna be bellows effect, trying to damper down the chimney or restricing the inlet air simply makes a charcoal farm out of the stove.

Your only hope of reducing the fuel load down to more ash and less coals is to let it rip with a higher volume of air moving through the primary into the stove and out the chimney. Long burn times with even consistent heat reducing the wood completely to ash like the good old days? Not happening with these, they just wont work that way by emmisions testing design.

You can still purchase quality stoves marketed as being for coal use only. There isnt a lick of difference in them today as there was back in the mid 80's when I sold them as being suitable for wood and or coal use. The manufacturers have simply changed their marketing propaganda to eliminate any mention of wood as a fuel source for them to meet coal exemption status.

Point is, you can still get a stove that will burn wood and heat like you would expect an old school stove to work. Just saying...

 

[cmsmoke]

My advice is to read your install/operators manual. Get the draft tested with an accurate draft gauge and compare to what the manufacturer calls for. Do the same with a moisture meter for your wood. If following the manual fails you, then try something different. Troubleshooting correctly will save you a bunch of aggravation in the end. "The draft will suck the door shut" or "my wood is dry as a popcorn fart" doesn't give any cut and dry numbers to find the right solution. A thermometer on the stove as well as the stack are also very beneficial to the operation of the stove. What you perceive as hot may not be the same as the manufacturers definition...once again without hard proof, you are at best, just guessing.

 

[Whitespider]

I’ll tell ya’ what cmsmoke,
I’m callin’ complete BS on your whole post. With the old style fireboxes I didn’t need to test my draft with an accurate gauge, use a moisture meter on my firewood, install thermometers on my stove and stack, or any other BS you want to come up with… and I had a lot of heat, a ton more than I have now. I know when my firewood is seasoned… I don’t need some fancy meter to tell me so. I know how much draft I have… I don’t need some fancy gauge to tell me so. And I know what hot is… when I can’t get within 8-feet of the firebox it’s damn hot. People have been heating with wood for thousands of years without fancy meters and gauges… and now suddenly we need those to get heat? That’s flat BS! If you want to believe some 50-year-old agency like the EPA has made it better by reducing (so-called) emissions… well help yourself. I ain’t buying it or the excuses or the technical BS. I could load the old style fireboxes with wood, set the draft and damper, and enjoy the heat for 6-12 hours depending… and no babysitting! If I now need fancy gauges, meters and thermometers… well SCREW IT then, I quit!

The biggest wood-burning mistake I've ever made was letting my guard down and believing some new, modern, government regulated thing would even come close to what has worked for decades of my life... shame on me!

 

[Whitespider]

...I almost never shut down my intake and use the flue damper once the fire is going. If I shut down intake I'll end up with a bunch of unburned charchoal. ...an old timer straightened me out. Ever since then I've had much better luck. Coal management is part of the stove, I let the coals go down to where there are only enough to easily light the next load of wood...

I've tried that... it didn't work.
If I have to "manage" coals, I'm not interested.
And if I wait for the coals to burn down my family would freeze... I heat my complete house 100% with wood.

 

[gregfox]

I've tried that... it didn't work.
If I have to "manage" coals, I'm not interested.
And if I wait for the coals to burn down my family would freeze... I heat my complete house 100% with wood.

I hear ya man... the first winter I was ready to give up on my POS EPA stove. I still question it and look for a different stove but it is what we have and have to get by with it. I have a tiny shoebox house that should be easy to heat but had trouble and hated my stove. The wife is home 24/7 and has learned to deal with the coals because I can't do it all the time as I typically work 60+ hrs a week. With winters like this and the last I heat 95%+ with wood. My shoebox sits out in the middle of a field and its a miracle my house aint blown away yet but when it gets real cold and windy it takes a little natural gas to help out upstairs.

I see your posts and dismay all the time and keep wondering when your gonna go back to an old smoke dragon... or are you gonna try to make your new piece work???

 

[Ayatollah]

I’ll tell ya’ what cmsmoke,
I’m callin’ complete BS on your whole post. With the old style fireboxes I didn’t need to test my draft with an accurate gauge, use a moisture meter on my firewood, install thermometers on my stove and stack, or any other BS you want to come up with… and I had a lot of heat, a ton more than I have now. I know when my firewood is seasoned… I don’t need some fancy meter to tell me so. I know how much draft I have… I don’t need some fancy gauge to tell me so. And I know what hot is… when I can’t get within 8-feet of the firebox it’s damn hot. People have been heating with wood for thousands of years without fancy meters and gauges… and now suddenly we need those to get heat? That’s flat BS! If you want to believe some 50-year-old agency like the EPA has made it better by reducing (so-called) emissions… well help yourself. I ain’t buying it or the excuses or the technical BS. I could load the old style fireboxes with wood, set the draft and damper, and enjoy the heat for 6-12 hours depending… and no babysitting! If I now need fancy gauges, meters and thermometers… well SCREW IT then, I quit!

The biggest wood-burning mistake I've ever made was letting my guard down and believing some new, modern, government regulated thing would even come close to what has worked for decades of my life... shame on me!

I think you both can be right. You have enough experience to make things work most of the time using time tested practices. cmsmoke uses mathmetics to confirm his situations. I recently had our house tested for heat loss by the gas company's contractor. They installed a doorway fan and then sealed of the entire house so they could tell how much loss there still was with all the doors, windows and such closed. Not much draw on that door fan; hardly noticable save for the smoke it immediately started drawing in through the fireplace insert. I thought I had more draw than that, and that it would take a lot more to cause it to reverse like that. In any case, mathematics is the language of physics. It never hurts to be able to communicate with mother nature when you have an issue where old world experience and new technologies collide.
I've noticed a few things in my burning years, and especially so lately. Fires are like economies; they are either growing or dying. The stove puts out more heat when the fire is on the growth cycle. Once it reaches a peak, the heat is no longer growing exponentially. also, some days are better than others outside. Maybe it's the dewpoint, the barometric pressure, or the rise of outside air that increases the draft to a near perfect state for a good burn, or colder air dropping down to earth that seems to act like the hand of god putting a field of pressure around your chimney and inhibiting performance of your burn. And all wood, dried or not, is not equal. Some of my recent eucalyptus struggles and smolders, while other sections of it burn like it was soaked in kerosene. It all camd from the same grove, at the same time, and was cut, split, and stored the same. It's like cuts of meat. Even from the same cow, some is tender and juicy, while other cuts are hard and stringy. Someone like whitespider might be able to spot the best cuts of wood for burning, but even an old sawbuck can be outsmarted by mother nature.
I'll leave with this last thought on that. I have been scrapping out some refrigeration equipment lately, and it's something I've done nearly my whole life. I can tell red brass from yellow brass, and stainless steel from aluminum at a glance. but recently the scrap yard got real techno on me. they brought out a machine, hand held, and no bigger than a geiger counter, that was placed up against the metal, and it tells what kind of metal is in there, in what concentrations. It can pare down the percentages of the alloys in just a few seconds. They tell me it costs like 30K for one, but when you have to depend on employees to make a buck for you, and you can't impart 30 years worth of wisdom on them during a 6 month or even one year training period, you look to numbers and technology to fill the void. Math matters.

 

[Whitespider]

I see your posts and dismay all the time and keep wondering when your gonna go back to an old smoke dragon... or are you gonna try to make your new piece work???

I'm not gonna' swap-out the unit during mid winter, we'll just suffer through, but I can just about guarantee there well be something else in it's place.

I thought about cutting this one apart and using some of the plate steel to build something (and I still might) but I think I've found just what I'm looking for... and it's priced about the same as one LP tank fill-up. No electronics, no bi-metal dampers, simple manual control; has a firebrick grate system (rather than cast iron), large ash drawer/door, combustion air intake under the grate! It does have a glass door with the associated air wash (air coming in from the top), but as long as it also has the lower (under grate) draft control I'm OK with that... besides, I kind'a like being able to check the fire with a glance. Dimensions are perfect for where I would place it... in fact it's narrower than what I have now, abut the same height as what I have now (counting the concrete block), and just a bit deeper. It will even take firewood up to 25-inches long.

Englander 28-3500 add-on furnace... I understand Lowes and Home Depot sell them under the name "Summers Heat". I'm gonna' stop and have a gander at one next time I'm passing through the big city... and if I like what I see, I'll start watching the sale ads. I was talking with a friend (in Wisconsin) on the phone the other day who told me he has one and loves it... replaced an ancient old, cast iron, smoke belching monster with it and now uses just half as much wood. His house is somewhat larger than mine (and just as old) and he claims it will heat them out'a the house. So far I haven't seen any negative reviews about the unit.

 

[TJ-Bill]

Update for everyone.

I installed the damper tonight.. and emptied out the stove (2 buckets)

Now I understand whats being said about the air needing to get to the bottom of the fire, My stove actually has a small intake the draws air directly to the bottom. Part of my problem could be that it was to full of ash to allow air to enter. That being said I still have never been happy with the way the stove has worked, To me the fire has always been to fast. I'm going to play with it and see what works best for my situation. I can already see a difference with the damper IMO but the firebox is empty and I'm thinking the stoves works it's best like that. I guess the test will come tonight.. it's supposed to be COLD!

 

[Ayatollah]

Update for everyone.

I installed the damper tonight.. and emptied out the stove (2 buckets)

Now I understand whats being said about the air needing to get to the bottom of the fire, My stove actually has a small intake the draws air directly to the bottom. Part of my problem could be that it was to full of ash to allow air to enter. That being said I still have never been happy with the way the stove has worked, To me the fire has always been to fast. I'm going to play with it and see what works best for my situation. I can already see a difference with the damper IMO but the firebox is empty and I'm thinking the stoves works it's best like that. I guess the test will come tonight.. it's supposed to be COLD!

Mine burns wood a little faster than I'd like to see too, and I installed a damper. It did help some, but it also increased the creosote build-up to concerning levels. 1 month and half or so and the screen at the top of the chimney cap was oozing creosote, and half plugged. If all you have is red hot coals, the damper seems to help hold in heat. But trying to use it to control an actual fire seems to help, but cause excessive creosote. My sister has a different brand of stove, and they get long burns and high heat. I guess we're all still at the mercy of each stove's design, and how compatible they are with each application

while I was up on the roof checking the chimney cap yesterday, clean this time by the way, I lifted the plate that seals the liner and cap to the brick chimney, and there was a blast of hot air that came out. Kept coming too. It's a two story chimney, and the heat build-up at the top is a lot more than I ever thought it would be. The pressure was higher there than what was coming out of the stainless pipe while the fire was going. We don't have a surround between the insert and the original brick, because it was not an even design and the one included with the insert wouldn't have worked. I'm thinking about a little insulation and sheet metal to create a barrier now, because that was an awful lot of hot air trapped in there

 

[Whitespider]

TJ-Bill,
I included a flue damper with my install (picture attached) because I figured having one and not needing it was better than needing one and not having it. My old brick chimney runs through the center of the house, always warm and has a ton of draft. When I open the clean-out it will suck a sheet of notebook paper off the basement floor and send it several feet in the air above the house.

Now I know every stove and every install is different, but here's what I've learned about using a flue damper with my EPA, secondary burn firebox. Closing the flue damper too far changes the burning characteristics dramatically, causing the stove to create more smoke then the old smoke dragon ever did (probably because primary air does not come in under the fire)... it will cause the secondary to kick in late and shut down early. I've found the best way to set it is to get a fire going, open the door, slowly close the damper until you see a little smoke exit the open door, then open the damper just enough to keep all smoke exiting through the flue. Closing it any farther will just reduce air flow velocity through the firebox, meaning less air forced down and into the coal bed, resulting in an even worse coal build-up in the bottom of the firebox.

A coal bed needs air (oxygen) to burn screaming hot, lots of air, and it needs to get to all the coals. The only way that's gonna' happen is if the primary air comes in below below the coal bed, flows up through a grate of some sort, and then up through the coal bed. This causes the coals on the bottom to burn hottest, as they burn their ashes fall through the grate and the next layer of coals get the blasted with the air. There is no possible way this can happen in a firebox that burns directly on the firebrick floor, and made even worse by bringing primary air in from the top. As the fire collapses into a bed of coals... it basically puts the lower layers of coals to "sleep" because little air can get to them. Air comes in the top, flows down along the door (air wash) and across the top of the coal bed and as the air heats it rises to exit the flue. Now here's the problem with that... the firebox depends on velocity to drive the air down into the stove, the more air exiting, and the faster it exits, directly effects the velocity of the incoming air. Well, as the fire collapses into a bed of coals and puts the lower coals to sleep, the fire cools slowing the exhaust... which reduces intake velocity. And as the top coals ash over less air is getting to them, causing the fire to cool even more. Eventually near all the incoming air is reversing itself and exiting the flue before it can even get to the coal bed. Now you have a slow smoldering bed of coals... making very little heat... and they won't burn down to fine ash for several hours. As they slowly burn they make ash, the more ash mixed with them, the slower they burn... It is a totally idiotic design forced on us by tree-huggers and their friends at the EPA.

The 85% efficiency does you absolutely no good if the box can't make enough continuous heat to keep up with demand... and made even worse when you start throwing out warm coals and dead pieces of charcoal (all potential heat) to make room for more wood. All I ever hauled out from the old smoke dragon was fine ash. When it gets real cold out my (so-called) high efficiency EPA firebox uses more wood than the old smoke dragon ever did (because I'm wasting so much potential heat in the trash to make room for more wood), and I never had to babysit the dargon either... just fill-it-and-forget-it.. But... but... I'm not sending any smoke out the chimney which makes the tree-huggers happy... whatever, they can kiss my...

Anyway, my point is... if you close that flue damper too far your problems will just get worse... or, at least mine did.

 

[Ayatollah]

TJ-Bill,
I included a flue damper with my install (picture attached) because I figured having one and not needing it was better than needing one and not having it. My old brick chimney runs through the center of the house, always warm and has a ton of draft. When I open the clean-out it will suck a sheet of notebook paper off the basement floor and send it several feet in the air above the house.


A coal bed needs air (oxygen) to burn screaming hot, lots of air, and it needs to get to all the coals. The only way that's gonna' happen is if the primary air comes in below below the coal bed, flows up through a grate of some sort, and then up through the coal bed. This causes the coals on the bottom to burn hottest, as they burn their ashes fall through the grate and the next layer of coals get the blasted with the air. There is no possible way this can happen in a firebox that burns directly on the firebrick floor, and made even worse by bringing primary air in from the top. As the fire collapses into a bed of coals... it basically puts the lower layers of coals to "sleep" because little air can get to them. Air comes in the top, flows down along the door (air wash) and across the top of the coal bed and as the air heats it rises to exit the flue. Now here's the problem with that... the firebox depends on velocity to drive the air down into the stove, the more air exiting, and the faster it exits, directly effects the velocity of the incoming air. Well, as the fire collapses into a bed of coals and puts the lower coals to sleep, the fire cools slowing the exhaust... which reduces intake velocity. And as the top coals ash over less air is getting to them, causing the fire to cool even more. Eventually near all the incoming air is reversing itself and exiting the flue before it can even get to the coal bed. Now you have a slow smoldering bed of coals... making very little heat... and they won't burn down to fine ash for several hours. As they slowly burn they make ash, the more ash mixed with them, the slower they burn... It is a totally idiotic design forced on us by tree-huggers and their friends at the EPA.

Sounds like a possible "fix" is to experiment with a tube with jets installed along the bottom, and controlled with some sort of device.

On a second note: That's more draft than I could ever think of generating, and I have a two story plus chimney. that may be something to look into itself. I'm getting too much draw with that already.