barometric dampers-Why Not Outside?

barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 6:00 am

Greg & I have been PM'ing each other in re my situation in which I don't see a benefit (for me) of a barometric damper. I had one years ago but never saw a benefit)
I have never noticed a time when my stove temp would actually increase, unintentionally.
I'll post the questions that I asked Greg, that I just can't seem to wrap my brain (what's left of it :lol: ) around:

1.If the chimney's draw is increased due to occasional wind gusts, wouldn't that draw be pretty effectively limited by the amount of air I'm giving the fire at the stove's air intake, unless we are talking hurricane force winds? :lol:
2. Wouldn't a baro damper work the same if connected to the outside of the chimney (through a pipe run up from the exterior clean out door & run up into the flue) to even out pressure differences caused by wind gusts, but do so without wasting stove warmed interior air & drawing cold air into the house to replace it? (the outside baro damper would have to be plastic to avoid rusting...Like a clothes drier vent.)

Physics Thinking:

Situation: No wind...32* outside air temp.
1. I start my stove & open my air vent 2 notches...stove temp 220*

Change in Situation: An hour later, the wind is howling outside, (across the top of the chimney) causing more draft (lower pressure in the chimney) & therefore, sucking more air through the coal fire. (I would assume that stove temp would rise a bit & coal usage increase....but I have never noticed this happening to me)

For those whose stove does increase in temp, If you introduce a baro damper into this equation (to dampen any internal chimney pressure changes by introducing more air into the flue) wouldn't it work the same way whether it's located inside (near the stove) or outside on he chimney itself? (but outside it would not be wasting stove warmed interior air)


I just have a natural aversion to seeing stove warmed air sucked out of the house & wasted up the chimney, for no visible benefit to me. :) (what am I missing/not understanding?)

Possible reason for my seeing no difference: After 26 years of use , I'm sure my chimney is not air tight & wind gust variations may be drawing outside air into the chimney through cracks & air infiltration around the clean out door


EditL: How about this experiment: (seal your damper closed, if you have one)
1. Take a large fan & tie it to the top of your chimney so that it's blowing across the top to simulate high winds.
2. Set you stove to maintain a constant temp
3. Turn on the fan & watch the stove temp


What should you see?

Stove temp increase?...Open Baro damper........ Return to the original temp? Maintain the higher temp?
how about if you introduce an exterior baro?...any difference over an interior one?
Last edited by Devil505 on Wed Sep 17, 2008 7:26 am, edited 3 times in total.
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000

Re: barometric dampers-Why Not Outside?

PostBy: gambler On: Wed Sep 17, 2008 7:17 am

I know nothing about hand fired stoves but with my stoker if I blocked off the baro I would stand a good chance of a hopper fire because the chimney would have a strong enough draw to pull air through the hopper and ignite the coal in the hopper. I too have thought about the outside air for the baro but I believe it would cool the chimney too much.
gambler
 
Stove/Furnace Make: Leisure Line
Stove/Furnace Model: Pioneer

Re: barometric dampers-Why Not Outside?

PostBy: coaledsweat On: Wed Sep 17, 2008 7:28 am

The baro must be in the same room as the appliance to maintain the proper relationship with the coal fires actual draft through the stove NOT THE CHIMNEY! Don't forget that your appliance is in a fairly well sealed box (your home). By placing it outside, it will no longer balance the chimneys draft to the stoves needs but to the chimneys relationship with the outside air pressure, this will usually amount to nothing. You can't reinvent this wheel. For your own saftey, do not attempt to, the heat lost to a baro is nothing compared to what it saves so install it as recommended only.
coaledsweat
 
Stoker Coal Boiler: Axeman Anderson 260M
Coal Size/Type: Pea


Re: barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 7:31 am

gambler wrote:I too have thought about the outside air for the baro but I believe it would cool the chimney too much.

Excellent Point!

BUT......(thinking out loud here)


Since the stove is still exhausting hot gases up the chimney, wouldn't that still cause enough draw to pretty much negate the cooling effect of the introduced outside air? (think I'll go back to figuring out "String Theory"....a simpler problem ....b4 my brain explodes! :fear:
Last edited by Devil505 on Wed Sep 17, 2008 7:38 am, edited 2 times in total.
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000

Re: barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 7:35 am

coaledsweat wrote:The baro must be in the same room as the appliance to maintain the proper relationship with the coal fires actual draft through the stove NOT THE CHIMNEY!


I have no doubt that you are right here......I'm just trying to follow the reasoning. Is it possible that my home's being well protected from wind negates my need for a baro damper?
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000

Re: barometric dampers-Why Not Outside?

PostBy: greentjdude On: Wed Sep 17, 2008 7:38 am

i wouldnt put it outside. it might work but i would end up with a bird or something building a nest in it. with all the snow and freezing rain in the winter there is probably a good chance of it not working properly by being stuck open or closed. i guess to fix that you could build an enclosure around it.
greentjdude
 
Stove/Furnace Make: Russo
Stove/Furnace Model: C-80

Re: barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 7:41 am

greentjdude wrote:i wouldnt put it outside. it might work but i would end up with a bird or something building a nest in it. with all the snow and freezing rain in the winter there is probably a good chance of it not working properly by being stuck open or closed. i guess to fix that you could build an enclosure around it.


1. Plastic baro damper...no rust
2. small enclosure with inlet screening...Protect it from weather & animals/birds
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000

Re: barometric dampers-Why Not Outside?

PostBy: Wood'nCoal On: Wed Sep 17, 2008 7:58 am

Is it possible that my home's being well protected from wind negates my need for a baro damper?


Dev, you need to buy or borrow a Man-O-Meter. Connect it up and get that stove cooking and check the draft. Checking it on a windy day would be the best. That would give you the answer on whether or not you need a baro. I'll bet you'll find it would be a help.
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Wood'nCoal
 
Stoker Coal Boiler: 1959 EFM 350
Hand Fed Coal Stove: Harman Magnafire Mark I
Coal Size/Type: Rice and Chestnut
Other Heating: Fisher Fireplace Insert

Re: barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 8:11 am

Wood'nCoal wrote:Dev, you need to buy or borrow a Man-O-Meter. Connect it up and get that stove cooking and check the draft. Checking it on a windy day would be the best. That would give you the answer on whether or not you need a baro. I'll bet you'll find it would be a help.



Wanna know why I don't want to try it John?..........

You really wanna know??



Well just for THAT........I'm not gonna tell ya!! :lol: (figured we needed a little Ralphy Boy here)




Why?......because I'm afraid....That's why!!



Last winter, after years of saying a distribution fan on my stove would be no benefit, I tried it &.....What a difference!!

Now....I'm afraid that if a baro damper really does save coal, I'll be mad that I wasted over 20 years running my stove inefficiently!.......Ignorance is bliss! :lol: :devil:


Another Reason:

I don't like the name "Man-O-Meter"....sounds like I should be wearing pink work gloves when I hook it up! (the device (below) would seem to fit a Man-O-Meter's name better) :lol:
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Last edited by Devil505 on Wed Sep 17, 2008 8:37 am, edited 5 times in total.
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000

Re: barometric dampers-Why Not Outside?

PostBy: greentjdude On: Wed Sep 17, 2008 8:19 am

i still like the inside way better, im not taking off my slippers and putting on my boots to make sure its ok every time i check the stove :P im definitly gonna have one installed on my stove inside, the wind is brutal on this hill i live on.
greentjdude
 
Stove/Furnace Make: Russo
Stove/Furnace Model: C-80

Re: barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 8:23 am

greentjdude wrote:i still like the inside way better, im not taking off my slippers and putting on my boots to make sure its ok every time i check the stove :P im definitly gonna have one installed on my stove inside, the wind is brutal on this hill i live on.


Do they require readjustments after the initial installation? (I thought once balanced you leave hem alone?)
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000

Re: barometric dampers-Why Not Outside?

PostBy: greentjdude On: Wed Sep 17, 2008 8:42 am

we have always adjusted the one at our family cabin so that it would "flutter" when there were gusts. we would do this every time after the fire was buring for a few hours. this is a cabin stove, it would only be used a few weeks a year so it sat idle a lot. this is going to be my first winter burning coal at home so ill check it more often. im sure others will tell you if its a "set it, forget it" thing. i know at the cabin when the baro stuck closed the one year, the fire was super hot when the wind kicked up! with the baro working there is a much more even heat. this stove is a surdiac that adjusts itself with an intake flapper and the wind was too much for it to handle. (i wish i had that stove here now! great little stove.)
greentjdude
 
Stove/Furnace Make: Russo
Stove/Furnace Model: C-80

Re: barometric dampers-Why Not Outside?

PostBy: LsFarm On: Wed Sep 17, 2008 9:03 am

Dev, it's pronounced Ma NOM eter,,, now, put away the pink leotard.. :lol: .

You don't want the baro outside. It functions correctly only inside..

Greg L.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: barometric dampers-Why Not Outside?

PostBy: LsFarm On: Wed Sep 17, 2008 2:24 pm

Dev, to answer your other question about the effectiveness of the air control on your stove I'll use a garden hose for example.

If you had a nozzle for your garden hose that was nothing but a cap with a 1/4" hole drilled in it,, screwed on the end of your garden hose.. Lets say your water pressure is 30 psi.. you would get X amount of water out of the hose through the 1/4" hole per minute..
Now, using the same hose and the same cap with 1/4" hole but you double the water pressure to 60 psi. You would get roughly double the amount of water per minute out of the hose and 1/4" hole.. there are many factors that will reduce the amount of water to less than exactly double,, but you WILL get a lot more water through the 1/4" hole with double the water pressure..

OK, flip the idea around,, lets say your chimney is drawing at .05" wc, and with this amount of draw [suction in the chimney] you need to have your combustion air vent open 1/4".. this amount of air feeds the fire enough to generate the amount of heat you want.
Now, apply your weather scenario, the temperature drops [big increase in chimney draft] and the wind picks up a lot, [an even bigger increase in chimney draft]. So now lets say that your chimney is averaging a draft [suction] of .10" wc, this is double the draft.
With the same 1/4" opening in your air control, you will get roughly double the amount of air feeding your coal fire, this will increase the burn rate, increase the heat in the stove. The increased heat in the stove is being drawn up the chimney by twice the draft [suction], so the temperature of the flue goes way up.[more draft], More very hot air from the stove is going up the chimney, the fuel is burning faster, and the stove may not even be hotter, the heat may be just going up the chimney.

With a Barometric damper, the draft will stay at your first setting, .05" wc, the flapper will allow some room air, at 70* to enter the flue pipe to control the strong draft, but the chimney won't be pulling 500-1200* air from inside the stove up the flue. The same 1/4" combustion air opening will still be feeding the same amount of air to the coal fire, the burn rate will be the same, and the stove temp will be the same.. everything stays very close to the same..

This consistant burn rate despite the radical weather change is what a barometric damper is designed to do, provide consistant draft to support consitant burn rate.

Instead of looking at the flapper of the baro damper when it is opening from a gusty wind, and thinking " look at all the heated room air that is going up the chimney' you should be thinking, "look at all the HOT 500-1200* air that is staying in my stove to heat my house instead of being sucked up the chimney " .

Greg L.
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: barometric dampers-Why Not Outside?

PostBy: Devil505 On: Wed Sep 17, 2008 2:37 pm

LsFarm wrote:Now, apply your weather scenario, the temperature drops [big increase in chimney draft]



I never thought of a temp difference problem. I'll have to watch the stove temp carefully this winter. I should see a stove temp rise just from a drop in outside temp, due to additional draft? (I never noticed that effect but now I know to look for it) How significant a stove temp rise would........ say a 20* outside temp drop cause if my stove was say....200*. (just a ballpark so I know what to look for)
That actually seems like a nice benefit if the stove temp would actually rise just due to an outside air temp drop. :)

(going back to my "String Theory" calculations) :lol:
Devil505
 
Stove/Furnace Make: Harman
Stove/Furnace Model: TLC-2000