Why exhaust damper on wood stove?
JohnT8
| Posted in Energy, Heating & Insulation on
I can remember people telling me that a damper on the exhaust side of the wood stove was a good idea, but I don’t remember why. Even when the air intake has a damper, they said to put an exhaust one on too… safety issue I think.
Someone jog my memory here.
jt8
“One of the fondest expressions around is that we can’t be the world’s policeman. But guess who gets called when suddenly someone needs a cop.” — Colin Powell
Replies
unh, can help adjust the draft, can close off the chimney when not in use...need more reasons?
Greetings JohnT8,
As a longtime poster you are worthy of a memory jog.
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
#1
Helps control draft so less heat is wasted especially at night
#2
Partially shuts off airflow to chimney in case of a chimney fire
#3
Provides something else to remember to do, or to confusicle you
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I am considering a small wood stove to heat my garage/woodshop. The garage is 20 by 20. I am going to insulate the roof and doors. The stoves are very inexpensive but I'm being told that the pipe I need costs about $150 per 4 foot length which would cost a multiple of the stove. Does that sound right? The pipe will go through the wall of the garage and up the side outside. I like the idea of burning wood, especially scrap to heat the shop but am trying to spend something like $1500 for the wood stove and pipe when I could probably get a small gas furnace for about $300 not counting the cost of running in a gas line.
Guys around here buy metal drain pipe and install that. Where are you located?
Sounds like you're talking about some high end multi-wall stainless at that price. That's almost 4bucks an inch and around here standard single wall 6 inch is more akin to like a $1 an inch.
Check the internet and see whats available there.
Cheers
every court needs a jester
Edited 3/1/2007 2:16 pm ET by rez
I live in NJ. That price was quoted from a local store that sells higher end in home wood stoves and fireplace inserts. What you wrote is what I was hoping to hear.
I'll check the internet for stove pipe. Isn't there a special section called a bezel for where the pipe goes through the wall?
The insulated pipe I saw on the internet runs around $35 a linear foot. Uninsulated pipe is about $1 per foot. I can't figure out what I need to use.
Hang on, help is on the way. View Image
every court needs a jester
No..No.. NO.
After the pipe exits the heated space you NEED an insulate pipe.
Or a chimney of masonry. Period.
so if I understand correctly. I use uninsulated pipe from the wood stove to the ceiling, a support box in the ceiling, insulated pipe through the ceiling and through the roof till it tops off about 3 feet above the ridge line.
Yes. 3' min. from any part of the roof within 10' on the horizontal. That is base rule, you may have resrtictions/rules in your locale.
But for sure, when the single wall pipe makes a transition to triple wall or double wall, it MUST be contained in the support box. I personally made mine ( transition that is) on the heated side of the roof plane, but I can't see your set up, I can only tell you the law as I percieve it.
Any single wal pipe in an unheated space( like the attic) is prone to cooling the gases and creosote build up, so..that space needs an approved flue, just like it was installed outdoors.
It's 2' higher than the highest point 10' away, by code. "But to be honest some folks here have been pushing the envelope quite a bit with their unnecessary use if swear words. They just put a character in to replace a letter. But everyone knows what they're saying." Sancho
A photo of how it should be done...
every court needs a jester
That is a nightmare. What is that, gravity furnace ductwork?
Can't imagine why the house burned down.
jt8
"The flower that follows the sun does so even on cloudy days."--Robert Leighton
How long would it take andy to learn this lesson?
be a snort
every court needs a jester
Apparently he learned something...
every court needs a jester
real indians didn't need no stinking chimney pipe.
jt8
"The flower that follows the sun does so even on cloudy days."--Robert Leighton
View Image
Sometimes it's amazing how long things can go on...
every court needs a jester
That's too funny...back when Sphere was cryin' cold, I tried to pass along that same stove on the right...Ashley Automatic...great little stove...Mrs 'Snort put the kibosh on sending him the Fisher Grandpa Bear...she's saving that to bury me in<G> "But to be honest some folks here have been pushing the envelope quite a bit with their unnecessary use if swear words. They just put a character in to replace a letter. But everyone knows what they're saying." Sancho
I kinda liked that old clock.
Those pic came courtesy of an old photojournal paperbound from the middle 70s 'Woodstock Handmade Houses'.
Another good one is 'Renegade Houses'.
plowmen dig my earthnone of them know along the linewhat any of it is worth
every court needs a jester
One theory is that you can cut it off if you have a chimney fire, but that would of course throw the smoke from the stove into the room.
Certainly on fireplaces and old-fashioned stoves the damper is used to limit the draft and prevent the fire from burning hotter than desired. If you have a reliable damper on the air input side (not just vents than can be opened/closed) that would seem to suffice for this purpose, though.
"that would of course throw the smoke from the stove into the room."No it won't - unless you are stupid enough to open the door when the damper is closed.In the event of a chimney fire, any slowing of the air flow is a very good thing. The damper still has a small hole in the center and the edges do not fir perfectly tight.I know from experience that a damper helps slow a chimney fire drasticly.
and adds no smoke to the room.
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"...unless you are stupid enough to open the door when the damper is closed."
How many of here on BT have NEVE done something stupid ???
(-:
His mother should have thrown him away and kept the stork [Mae West]
OK, I'm chastened.That sort of error is imminently more likely when in full blown panic mode from the roar of a chimney fire.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I'd definitely put one on.
Even if your stove is an airtight one they can come in handy. The door gaskets aren't perfect and don't last forever. When you have a small leak it can be difficult to control a fire.
They're cheap and easy to install, so there's no real reason NOT to ahve one.
Can't really see it in this picture, but I've got one. I knew it was a good thing, but couldn't remember why, so I went ahead and had chimney guy put one on while he was doing the pipe. But I kinda wanted to know WHY I had it put on. ;)
View Imagejt8
"One of the fondest expressions around is that we can't be the world's policeman. But guess who gets called when suddenly someone needs a cop." -- Colin Powell
Just to be sure, though, I would check the installation manual for your stove (if there is one) I may be remembering incorrectly, but I think I've seen instructions for a stove at least once which specifically said NOT to install one.
Was probably an "airtight" stove where they already had it choked down enough that they didn't want to add any more reason for creosote to form.
Don
I had a Morso that the installations manual instructed that NO external damper was to be used.
did it have a built in damper?
"there's enough for everyone"
Not that I recall. It has been a number of years now so I may not be accuratly remembering.
My memory is that they claimed the draft control would control the fire and that an external damper would disrupt the most effective burn .Edit. I just looked at the PDF for the MOrso 2B Classic which is what I had and it shows no internal damper that I could see.
http://www.morsoe.com/NR/rdonlyres/388827BD-4F8D-4106-8946-3CE13833ACBE/0/2BClassicNA.pdf
Edited 2/6/2007 10:32 pm ET by dovetail97128
question: 'Why exhaust damper on wood stove?'
answer: to control the fire -
the various/varying quality of fuel and the various/varying atmopheric conditions make a exhaust damper on a wood stove a necessity to gain good performance -
basically tuning the draft and damper allows for the best burning conditions -
open draft/open damper - upon startup/refuel -
open draft/'closed' damper* - maximum heat out of established fire (* 'closed' and 'open' being relative here, not '100%')
closed draft/closed damper - slow fire down/long burn time/low heat output -
closed draft/open damper - hmm....that's an unusual one - maybe a good burning fire under poor drafting atmopheric conditions/heavy air -
the exhaust flow in the chimney is not simple - there can be circular flows -
hey - it's another control - it's good -
Responding to a chimney fire requires a calm approach and common sense. In some cases, opening the door to the stove and discharging a fire extinguisher into the firebox is a useful strategy. The draft will, of course, carry the extinguishing chemicals upward. Immediately closing the stove door and dampers to limit oxygen supply would be the next step. In some cases it may be necessary to then notify the fire department; however, I've managed to calm down a chimney fire before without professional help.
You really should call the FD first. We carry the equipment on the trucks to look for extension we can be sure that the fire you put out is out.
Most home owners do not possess this skill.
open draft/'closed' damper* - maximum heat out of established fire (* 'closed' and 'open' being relative here, not '100%')
Hmm.. so the nearly closed damper doesn't choke it off? I had just been controlling the burn with the draft, but if the combination allows more control, I'm all for it.
jt8
"One of the fondest expressions around is that we can't be the world's policeman. But guess who gets called when suddenly someone needs a cop." -- Colin Powell
if you have a good drafting chimney, the damper is very useful - I burn into isulated SS chimneys - they heat up fast and draft well - creosote is not an issue -
right now I have two fires going - the main heating stove (Jotel #4) is in cruise mode, with the draft at 100% and the damper at 20% (80% closed) - interestingly, the damper on this stove is built in, right before it hooks to the stovepipe - shifted to the left, it will close 100% - there is a detent at full open, and to the right, a detent at 50% shut and a detent at 80% shut - to the left it will not close off totally -
the other fire is in the cookstove (I've got French Onion soup started for tonight) - with this fire, the key is to turn the oven off, get a hot fire going and get the chimney well warmed, then turn the oven on - it cruises with the draft mostly closed and the damper turned down about 35% (35% closed) - it's a leaky stove (tho wonderful) and behaves much differently than an airtight - damper stays open till all is well warmed up -
"there's enough for everyone"
if you have a good drafting chimney, the damper is very useful - I burn into isulated SS chimneys - they heat up fast and draft well - creosote is not an issue -
That's what this one is hooked to. Double-wall pipe to the 8' ceiling and then the Selkirk supervent SS chimney pipe offsets-30 runs maybe 5-6' and then offsets back up and out. Drafts really well.
Do you have thermometers on your stoves? If so, what kind of temp do you shoot for? The wood stove thermometer I bought lists 'overburn' starting around 550, but my stove manual says 'optimum' burn is 500-600.
jt8
"One of the fondest expressions around is that we can't be the world's policeman. But guess who gets called when suddenly someone needs a cop." -- Colin Powell
My double drum has a built in damper in between the two drums. I HAVE to leave it wide open, else I choke the stove too much. A single drum was not like that,I could close it down at night for a longer burn.
The thermometer I have is mounted after the second drum and in order to keep it in the "Burn zone" I would be overfiring the main drum. So I ignore the actual three "zones" and use it more as general temp indicator of the exit flue. I too, burn hot enough that creosoting is a non-issue. I don't mind overfiring the burning drum for a short period, but prolonged would warp the door frame or pucker up the barrel.
You may want to adjust your burn temps to what the stove can handle and not think that the thermometer is the gospel for all stoves. Over firing your model would be a disaster as bad as a chimney fire would be. Cast steel or sheet steel will warp, cast iron will crack. I am sure you firebox is sheet steel and I have seen welds break when overfired.
Spheramid Enterprises Architectural Woodworks
The secret to a long life is knowing when its time to go. M. Shocked
Ive burned wood exclusively for 35 years. I haave always used a damper.That be said there certainly hasnt been any techn advances in them .Same old casting with the spring handle and the curly shaft.Problem is unles they are installed perfectly level and centered in the pipe the thing will always fall closed usually exactly as u open the stove!Im thinking of retrofiting mine with a long threaded rod so the damper stays and can be seen in the aspect u want.A couple nuts on the cast part and it wont flop around.
This one is welded to the pass thru rod after it is installed in the flue collar that bolts to the drum. PITA.
The last one when I was running a single barrel, actually had the pass thru rod burn up! Talk about overfiring..it took two seasons to do it, but it did. And of course EVERY store for miles was out of 6'' dampers, plenty of 8", but not a 6 to be had anywhere.
The coilly handle is oriented the same as the plate on this set up, so it is easyto tell...maybe thats why they welded it, I think if you rely on the spring tension to hold the plate, it is 90 degrees from handle to plate?
Spheramid Enterprises Architectural Woodworks
The secret to a long life is knowing when its time to go. M. Shocked
open draft/'closed' damper* - maximum heat out of established fire (* 'closed' and 'open' being relative here, not '100%')
I think you've got something there, I like this setting. If I set draft at around 75% and damper around 20%, I get the same heat as before, but the wood lasts longer. Previously I was leaving the damper wide open and dropping the draft down to about 40-50%.
jt8
"Being powerful is like being a lady. If you have to tell people you are, you aren't. -- Margaret Thatcher
you're welcome -
send firewood....
"there's enough for everyone"
send firewood....
Would have thought you'd be up to your eyes in wood. Don't you have a load of apple trees to go with those peach trees? Or are you selling all the apple wood to the slickers?
Ma thought she was doing me a favor by calling someone to deliver a load of firewood. He told her it was seasoned, about 2/3 oak, and a full 1/2 cord (not a face cord). Well, the following week when I finally got a look at it, my guess is that it is a face cord of mostly unseasoned walnut.
Strong wood smell, not weathered looking, no checks on the end and when I tried to burn a couple pieces, it takes forever to burn and the liquid just boiled out the ends. Looks like unseasoned to me.
jt8
"Being powerful is like being a lady. If you have to tell people you are, you aren't. -- Margaret Thatcher
that's a great metaphor for ethanol -
you use 80% of the energy conditioning the fuel, and get 20% of the output as useable energy -
thanks, Mom - - her heart is in the right place -
'seasoned' is not a legally enforcible term, I'd guess - looks fresh cut to me, probably tops out of trees felled in the last few months - split it small to get it to burn a little better - stack those small splits inside near the stove and get a bit of moisture out of them before you burn -
yesterday was the first day with a temp above freezing since jan 23 - we've burned thru a heck of a lot of wood - we'll make it, but the woodshed is a lot lower than I would have expected - and any new wood has the same quality as your walnut - can't get to the woods yet, too much snow - we'll work and get the shed full over the next month so we'll be ready for next year -
all I can think of is VaTom, sitting on his ### in the no hassle warm, reading, playing Breaktime, diddling the wife - while I haul wood -
"there's enough for everyone"
'seasoned' is not a legally enforcible term, I'd guess - looks fresh cut to me, probably tops out of trees felled in the last few months - split it small to get it to burn a little better - stack those small splits inside near the stove and get a bit of moisture out of them before you burn -
I'll probably just shift it to elsewhere in the yard and use it next winter (assuming the termites don't find it).
all I can think of is VaTom, sitting on his ### in the no hassle warm, reading, playing Breaktime, diddling the wife - while I haul wood -
I've got some friends that look for any chance to get away from dw for a while. They'd probably figure chopping wood was a good excuse.
But I guess you could pick up a second hand track-hoe somewhere and go crazy with that. Make a bunch of reinforced earth-sheltered or PAHS structures. Just think how much easier it would be to keep the produce at temp in a super insulated earth-sheltered structure. With a big door on the side to drive in and a fancy entry on the front for the folks to walk in and buy stuff. Looks like a small shop from the front, but just keeps going and going back into the hill. ;)
That stuff is on my top 100 list if I ever hit the Powerball. Earth sheltered complex. With nice big shop, maybe a gym, plenty of living space... all connected by underground tunnels (IL weather isn't any better than IN). Design it so that the whole complex uses about as much power as a regular 1500 sq ft house. :)jt8
"Being powerful is like being a lady. If you have to tell people you are, you aren't. -- Margaret Thatcher
No doubt that's walnut. My Uncle has plenty of dry wood if ya need some. But I know it's a fairly long trip down to get it.Once or twice I've swapped him some green wood for some dry wood when I've needed it. I'm sure he'd do the same for you if you ever make a trip down this way.
Q: Why is Bill Clinton so reluctant to deal with the fate of Elian Gonzalez?
A: Because the last time he made a decision about where to put a Cuban he was impeached
I was kinda wondering if I'd have enough from the first load to make it through. At the rate I had been burning it, it would last at most a week, but it is supposed to warm up this week. Maybe it isn't going to get back down to freezing, who knows?
The easiest thing would be to just call the guy in Ashland that I got the first load from. That was split nice and well seasoned. $70 face cord. I have no doubt that would get me through to warm weather. Good service and well seasoned wood. The only way to improve on that would be a higher % of oak/hickory and less hackberry/cherry. Which is what I think Mom was trying to get for me; a load of oak.
But I tell ya what, I keep track of who provides good service/goods and who doesn't. And that guy with the second load of wood is going on my "doesn't" list. So when a friend or co-worker asks me where to find firewood, the "doesn't" list isn't going to get recommended.
I'm not malicious, but I am a believer in "you reap what you sow." And I'm not shy about recommending folks to give good service or do good work.
jt8
"Being powerful is like being a lady. If you have to tell people you are, you aren't. -- Margaret Thatcher
Looks freshly cut to me. Remember that is the kind of wood that causes chimney fires!A face cord IS a half cord if the cuts are 24" long. It is a third of a cord if they are 16" long and only a quarter cord if they are 12" long
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Looks freshly cut to me. Remember that is the kind of wood that causes chimney fires!
Which is why I bought load #3 from the guy I'd gotten load #1 from. Seasoned hickory, oak, walnut, black cherry, hackberry, etc.. Unseasoned load #2 is still hogging the wood rack, so #3 got put in two piles in front. Front pile is directly on the crete, so I shifted most of it into the garage/house. It started raining promptly afterwards and continues to rain.
View Image
A face cord IS a half cord if the cuts are 24" long. It is a third of a cord if they are 16" long and only a quarter cord if they are 12" long
Yup. Which is why I usually ask them if their advertised "1/2 cord" is really a face cord. Some of them don't know the difference. The guy who I bought loads 1 & 3 off of told me up front that it was a face cord and that it was probably about 1/3 of a cord. Plus good service and a reasonable price (called him Sunday night..and it was delivered, stacked and waiting for me when I got to the house Monday). I think I'll stick with him when I need firewood.
jt8
"The flower that follows the sun does so even on cloudy days."--Robert Leighton
John, actually, walnut is not too bad creosote wise, even slightly green. But it does take a hotter start to get it sizzling. I'd not be afraid to split off the white sap wood/bark and suffer thru the kindling it takes to get it blazing.
I swear by mixed wood, I refuse to load my larder with just one specie of wood. Dryness falls in the same category, some nights I want a slow burn and I like maple for that, or pizz oak as we call it here..dense, dry, and heavy. If it is not numbingly cold, it works well.
Of course Hick, and Locust or Ash is a good medium burn, even when wet/snow covered.
I have dry hackberry and locust that will warp a stove if ya load it heavy.
Basically, ya have to learn what does best to your lifestyle of feeding and comfort level, add the unknown BTU of your chosen friable, and set your self on monitoring the OUT flow of what you are burning and how/why it is such.
I had a serious coal stove in Pa, I also had a wood shop, and the floor scrapings went into the coal stove, I also had cats..they loved the floor shavings as a litter box, So, I learned that even cat poop generates heat, but man, out plowing the driveway, the smell was intolerable...to each your own, my neighbor came up one day and said "WTF? You burning cat crap?".....Ayup. LOL.
We're almost done with the fire season, thank god..We set a new record a few weeks ago, one ton of wood in ten days.
I get a heap stacked on my Ford that is 4' wide ( and change) 8' long and 3'+ tall with out sides, 4' with. All dry mixed Cherry, walnut, oak, locust, hack, maple, osage, hick, and scrub..50 bucks, I load and haul, but man when that goes away in ten days, I get cranky real fast.
When your banking a fire in a stove for the night it can be good to hold the smoke down on the top of the fire to retard the burn rate. Especially with older non-airtight stoves the intake damper doesn't really shut things down as hard as you might need with dry wood to still have coals left in the morning to start the next days fire. So a chimney damper can help you not have to crumple newspaper in the morning. You probably don't need it if you have a good airtight wood stove.
The Napoleon I pictured earlier is in my project house, which I'm only at a few hours a day (except on weekends), so it can go 24 hours before I get back to it. The draft control is low-1 to 5-high. When I leave I usually dial it back to 3 or less, but I had been leaving the damper open. Monday when I went to fire it up, it had gone 18-19 hours without being fed. I stirred up the ashes and found enough orange to make for a quick re-start. So I don't doubt that if I was living in the house, I wouldn't have any trouble keeping it fired up over night.
And playing with the damper might extend it even further. Granted, it isn't putting out much heat there at the end, but if it keeps the stove warm (rather than 20 degrees or less), it seems to start up much easier and starts putting heat out that much faster.
jt8
"One of the fondest expressions around is that we can't be the world's policeman. But guess who gets called when suddenly someone needs a cop." -- Colin Powell
I have one on my stove, I've never used it, but I'm qlad it's there.
Your fire will last longer and give off more heat if you use it.
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I've got a little Vermont Castings Intrepid. It has an internal damper. The 6" single wall pipe goes up about 2' to an ell, then 2' horizontally, more or less, to the thimble...do you think I'd benefit from a pipe damper?When I heated with a honkin' Fisher Grand Pa Bear, no damper = no fire in the am<G> "But to be honest some folks here have been pushing the envelope quite a bit with their unnecessary use if swear words. They just put a character in to replace a letter. But everyone knows what they're saying." Sancho
Probably not, but I just took out an old intrepid. The cast internal damper was warped from too hot of fires from previous owners, so it never worked for me. Wioth the new stove and a damper on the pipe, I think I get twice the heat from the same wood.Even on the stove I have, if I forget to turn the damper at night, i notice a difference. The wood burns off faster, but about the same heat made to the house, all subjuective, of course.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
The damper was more common on stoves that were not air tight and some are still in use today.
Theres a box heater thats cast iron that has the cooking rings on top of it . It sells for 100 dollars at the tractor store and many others.
It doesnt have any seals and in my opinion must be ran with a damper .
That stove settled the South if Longhorns settled Texas.
That stove was so common to see in my earliar days . It was cheap then too and probably the reason so popular.
Then there was the King heater that aced in Ben Franklin fireplace mode.
You could open the stove up and use them as a fireplace or shut it up in stove mode at night . They were the rage for a while and they were not air tight . They too took a damper to operate.
When a stove is shut down with a damper it greatly slows the draft of course. Controlling the secondary burn in the box is much more efficient . So the finer stoves have dampers built in them to open up and run full steam ahead . After the stove reaches 600 degrees the draft in the stove can be redirected into an S flow design by shutting its damper and that will produce a secondary burn making it much more efficent . However they are what is called an air tight stove but in honesty , none really are.
Tim
Heck, after all of the brain damage from the drugs, why worry about killing more brain cells with carbon monoxide?
It can control draft better than many of the center screw air inlet adjusters, but it's still a pretty stupid idea, IMO
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