understanding upper and lower draft controls and how they work

[aaronmach1]

Guys when i understand how somthing works and what it actually does then i get a lot better results.
Can anyone explain to me how the lower ash pan damper works as opposed to the slider draft damper above the feed door, and then finally the damper in the stove pipe above my wood furnace? (englander 28-3500). I know that they add air when opened etc, but how do the different locations affect the burn differently etc. For example: differences of burning with top slider full open and bottom shut versus top slider half open and bottom damper half open. I just want to understand how to better work them for more effective burns. I guess ill be suprised to see responses to this, i havnt really found any good explaination on it yet. maybe its a learn from experiance only type of thing. Let me know what you guys think.

 

[NSMaple1]

The damper up in the pipe controls how much draft is available for the unit to use.

I don't like them, as draft the chimney sees constantly varies with weather conditions - therefore you would need to fiddle with it. And there's a risk a windgust could close it up some and create a low-draft condition which might allow smoke & CO to back up into your house. I would replace it with a barometric damper tuned to regulate proper draft. Once it's tuned, it will keep it there.

 

[XSKIER]

On my Hearthstone 1 I get long burn times with the intake air damper opened half way and the flue closed down to about one inch. No excessive coaling either. If I close down the intake air, too many cold coals a few hours later.

 

[aaronmach1]

but what is the difference in air being introduced above the fire with the above door slider versus air being introduced under the fire with the ash door dial?
Which one affects the fire more and how does it affect it?
The one i really dont understand is bringing in air above the fire with the slider above the feed door.

 

[XSKIER]

I'm not familiar with your englander, but I leave my secondary air tube inlet wide open all the time. Why not get an operator manual for your stove and see what it says?

 

[aaronmach1]

i not really meaning to sound specific on my model. Im looking for more of a scientific answer i suppose. On how the 2 different locations of incoming air affect the fire quality differently.And which one works better for certain situations.
Like, why does introducing air above the fire help anything? I can see air under the fire helping because heat rises.

 

[XSKIER]

Air below the wood affects the burn rate, air above the wood is for secondary combustion, and the flue damper regulates the volume of Draft.

 

[woodchuck357]

The only use , to me, for a damper is to shut off reverse air flow when the stove is not in use or to shut off air in case of a flue fire. The rest of the time it is left open. The draft control below is open and the one above as well as the secondary air are closed when starting the fire and when reducing the coal bed. When starting the fire any draft that does not bring air thru the kindling slows the start up by reducing the air flow where it is needed. The secondary air that comes in from the top is to add air to burn the gases driven out of the wood that don't completely burn at the level of the wood. The draft over the door does help provide secondary air but it's main purpose is to reduce the soot deposited on the glass in the door.

 

[aaronmach1]

thanks guys this helps me understand better!

 

[flotek]

That unit is a bit different on paper theory compared to actual real world settings * if your wood is dry * you want the bottom spin draft just cracked open a half or often just a quarter turn .. The spin draft has a dramatic effect on how much burn time your going to get . The slide should never need to be more than halfway open in my experience . Your draft speed and wood is going to put the settings all over the board . Air from underneath lights off the coals and generally puts out more btu but it eats wood as well think of the slide as the user friendly incoming air it's where the typical range of adjustment should be maintained

 

[Whitespider]

The Englander isn't designed as a secondary combustion furnace… that doesn't necessarily mean it can’t achieve it to at least some degree though. The main purpose for bringing air in the top is to “wash” the glass door and keep it clean. The, clean, fresh air “washing” down over the glass insulates it from soot and creosote build-up. Depending on how the air travels through the furnace before actually entering the firebox, it may also be pre-heated to some degree. That top air is your “primary” air feed… you need it to a certain degree or your glass will eventually turn black.

The ash door spinner draft is a “secondary” or supplementary air feed… you may, or may not need to use it depending on conditions. For (one) example, if you’re burning wood that coals-up heavily, such as elm, hard maple, oak and such, you may find opening that a bit more and closing the top slightly will keep the depth of the coal bed under control. Air coming in under the coal bed will cause it to burn hotter and faster than air washing over the top. It’s a balancing act and sort of a learning curve, what works for your set-up may not work the same with another… don’t be afraid to experiment a bit until you get a feel for what works when.

The flue pipe damper doesn't directly affect incoming air… it limits the outgoing gasses (smoke and heat). It does this by reducing the amount of “suck” the chimney can apply to the firebox. Of course, reducing “suck” will indirectly reduce the amount of incoming air… usually, that is. Often the flue pipe damper can be used to control flue pipe temperature without making drastic changes to the fire itself. It can also increase firebox temperature by reducing heat loss through the pipe, without actually “crankin' up” the fire. Some set-ups need a flue pipe damper to run correctly, some don’t… I always install one because I believe it’s better to have something and not need it, than it is to need something and not have it. My last old smoke dragon flat wouldn't heat unless the flue pipe damper was closed most of the way… I ain’t touched it for the current furnace; it’s been sitting wide-open since day one (I played with it a bit and didn't notice any measurable impact). One problem with a flue pipe damper is you normally need to open it up before opening the loading door or you’ll get a face full of smoke at times. And again, it’s a balancing act and sort of a learning curve… making changes to one affects all three.

If I were you, and if it will run OK without it, I’d leave the flue pipe damper wide open until I got a good feel for the primary and supplementary air feeds. Get comfortable with them before adding the third variable… and then you’ll also have a better idea of how it affects the others, as well as the heating efficiency. If the furnace won’t run OK without it… such as it seems to burn through a cycle way to fast, or maybe ain’t heating like you think it should… then close the flue damper maybe half or two-thirds way and leave it there while you get comfortable with the air feeds. If you start out continuously messin’ with three different controls you’ll just get frustrated… you’ll never really learn how one affects the other… and you won’t be able to duplicate positive results.

Don’t worry, you’ll catch-on to it faster than ya’ think… just look at it as a fun adventure into wood heating.
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[brenndatomu]

That top air is your “primary” air feed… you need it to a certain degree or your glass will eventually turn black.

The ash door spinner draft is a “secondary” or supplementary air feed… you may, or may not need to use it depending on conditions.
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Did spidey just say that you may or may not need air coming in from under the fire?! Sorry, I'll be back, I gotta go clean my drawers!

 

[Whitespider]

Well, you know me, I ain't about makin' any... "blanket"... statements
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[brenndatomu]

Well, you know me, I ain't about makin' any... "blanket"... statements, much
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Fixed it for ya

Aaron, my Yukon has both under and over the fire air like yours. I suppose that you will get the best advice from someone who has the same model furnace, but for me, I find that leaving the fire have at least a small amount (1/2 to 1 turn?) of air from under (ash drawer) at all times gives a cleaner burn. I would think you would want to control the burn rate with the upper control more so. But like others have said, you'll hafta play with it to find the best results from your particular install.
Getting a manometer to check your draft makes it easier to set your flue damper for best results. I have bought (2) Dwyer Mark II (model 25) manometers now, off fleabay for $20 or less delivered to my door. I have mine mounted on the wall next to the furnace, hooked up all the time. As others have said, a baro will give you the smoothest most controlled draft, but a manual damper and a manometer are effective too. A lot of people will say heck with the manometer, but I like to be able to see for a fact what the wind and temperature are doing to my chimney and how my damper adjustments are affecting things, but I'm a tool hound too, so...

 

[aaronmach1]

guys thanks so much for all the info, very helpful !!!
Whitespider, good lord! I feel like i need to pay for that much info! Thanks for taking the time to write me a how to book. Ill be rereading that many times tonight. That is better than the answer i was looking for and the idea of not adding the 3rd variable of the flue damper is a great idea and im going to try running it like you describe now! hopefully will shorten the learning curve here. This furnace operates so much different than my old one i cant beleive it. thanks!!!

 

[aaronmach1]

Fixed it for ya

Aaron, my Yukon has both under and over the fire air like yours. I suppose that you will get the best advice from someone who has the same model furnace, but for me, I find that leaving the fire have at least a small amount (1/2 to 1 turn?) of air from under (ash drawer) at all times gives a cleaner burn. I would think you would want to control the burn rate with the upper control more so. But like others have said, you'll hafta play with it to find the best results from your particular install.
Getting a manometer to check your draft makes it easier to set your flue damper for best results. I have bought (2) Dwyer Mark II (model 25) manometers now, off fleabay for $20 or less delivered to my door. I have mine mounted on the wall next to the furnace, hooked up all the time. As others have said, a baro will give you the smoothest most controlled draft, but a manual damper and a manometer are effective too. A lot of people will say heck with the manometer, but I like to be able to see for a fact what the wind and temperature are doing to my chimney and how my damper adjustments are affecting things, but I'm a tool hound too, so...

i like the manometer idea. And for that price im going to check one out. Thanks!

 

[aaronmach1]

lots of them on ebay
http://www.ebay.com/sch/i.html?_odk...w=Dwyer+Mark+II+(model+25)+manometer&_sacat=0

 

[brenndatomu]

lots of them on ebay
http://www.ebay.com/sch/i.html?_odkw=manometer&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0&_nkw=Dwyer Mark II (model 25) manometer&_sacat=0

Many more if you drop the (model 25), just FYI. My search went from 7 to 23 found by doing that...

 

[Whitespider]

Whitespider, good lord! I feel like i need to pay for that much info...

Heck, don't feel like ya' owe me crap man... really, that's why we're here, to help each other out, share information, and maybe learn something.
We just argue about tires, the EPA, and whatnot when there ain't much else goin' on it sort'a helps pass the time.
Anyway, just 'cause my post sounds like I know what I'm talkin' about don't necessarily make it gospel for your set-up, ya' still need to do your own experimenting... but I did kind'a keep it as "general" as I could without making too vague to be helpful.

Good luck with it man... and have fun with it‼ Keep us informed on how it's workin' for ya.
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[aaronmach1]

working very well that last couple hours. flue damper always open 100% ash pan door dial open 1/4 to 1/2 turn and slider above door open 1/2. I put a big peice of red oak in at 5:00 tonight and its still half there and ive added a couple small ash splits around it. Its got me in shorts in here! I think ill have a reds apple ale. (finish the last one, not real crazy about em, kinda sweet)