How Barometric Dampers Function, Why use a Barometric Damper

How Barometric Dampers Function, Why use a Barometric Damper

PostBy: dcrane On: Sat Mar 09, 2013 11:36 am

This may or may not bring some flame wars because people do have an exteem stance regarding the use of Barometric dampers vs/ Manual dampers but I was given an analogy recently with leasons regarding the use of Barometric dampers used in conjunction with manual dampers on hand fired coal stoves that was pretty impressive and thought it noteworthy enough to share with others, I will try my best to explain it as it was explained to me, I am making this new title thread because the main baro thread is the longest and most contrivercial thread in the history of the web and the "meat" of this would be lost to most :lol:

The purpose of a manual damper is to control the heat output of your stove ; when your to hot you open the manual damper thereby releasing that heat out the chimney. When your cold you would close the manual damper and open you air control knobs slightly to increase the heat output into your home.If you think about sucking on a tobacco pipe and the stove being the hot bowl of that pipe and your hand cover that bowl as you take a large sucking drag of that pipe… you will find that pipe bowl get hot and the tobacco in the bowl would turn bright red. If you take your hand off the bowl and take a large sucking draw of the pipe you will also find the tobacco turn red and the bowl still becomes hot (your just able to take a lot more of that heat/smoke from the tobaco/bowl very fast into your lungs).

Now… we can as humans control the rate or "suction" that we chose to take a drag off a tobacco pipe and make the tobacco burn slow, nice and even as we take that drag if we want. We cannot do that with the atmosphere and we cannot climb our roof and put our mouths around the flu pipe (well… maybe Fred can, but most of us cant :lol: ). This is where a barometric damper comes into play… A baro metric damper is like being able to drill a small hole in the side of the tobacco pipe stem which does relieve how much tobacco you can burn up in the bowl… it’s even better then that… it’s like having somebody with 1000 different size drill bits 24/7 day and night drilling the exact proper size hole in that pipe stem as determined by the force/strength of your drag on the pipe to maintain a forever even burning of the tobacco in the bowl thereby making that tobacco last longer. In my mind it would make perfect sense to have a manual damper on the stove side even if you decide to try a baro as well, this would in effect give you the ability to only loose the amount of heat from the stove you wish to send up the chimney instead of radiating into your living space.

There are some definitive drawbacks to the use of a baro but explained most of these drawbacks are inconciquecial by virtue of how the Baro functions;

#1 a baro does take a very small percentage of the heated room air and allow it to get sucked up the chimney and out of the house, but remember that when it does this its only doing it at times the draft is very high (in which case your stove is probably performing strong and hot and you want to be cooling it down during those times anyways so your not sweating out of the living room). One of us wil have to work on a product that extends the Baro mouth to an opening to the basement so its drawing this air from an unfinished basement LOL, it does make sense to me to keep the Baro at a low spot on your flu as possible as opposed to a high spot (since your rooms hot air is high and cooler air is low)

#2 If you have a lousy drafting chimney or a borderline draft then a baro makes no sense for you (it can NEVER improve draft, ONLY regulate a good draft). If your not producing enough draft as it is then you don’t need a Baro to regulate anything.

#3 you now have another piece of equipment that you need to keep clean and maintain (the bright side is…if you don’t have a removable baffle in your stove then the baro may allow you an easy access point with a small hose vacuum to clean out the baro, manual damper and elbow without disconnecting your stove).

So… the times a Baro is in place and in use should be when you have a good drafting chimney and as such it can only be concluded that the use of a Baro can save you up to 50% of your fuel per year because without it you are still sucking on that tobacco pipe and all your suction is going to go directly at the bowl of that pipe unless you relieve that pressure by drilling a hole in the stem or opening your mouth a lilttle to draw air from someplace else (like a Baro allows).

It is certainly possible to use your draft controls and a manual damper to attempt to gain some coal savings or better described: to gain more heat from each ton of coal you do burn, but to do this with the sort of 24/7 efficiency of a Baro would require you to literally stand next to your stove all day and night 24/7 with one hand on the manual damper and one hand on the draft control.
Most of you that know me, know I don’t use a Baro… but since I’m setting up a new stove, hearth, flu this year and after spending a day with Larry going through a multitude of stove design flaws, problems, positives, negatives, etc. (this is one of the discussions/debates he won with me) and I’m convinced its worth trying and I will gladly change my position if I can save up to 50% of my solid fuel costs! I will be posting after next season my results and fuel savings

Credits to Larry Trainer of Chubby Stoves
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Lightning On: Sat Mar 09, 2013 3:02 pm

Mr. dcrane. .. I'm curious. How much experience do you have burning coal?
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut/Stove Size Mix

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: dcrane On: Sat Mar 09, 2013 5:18 pm

Lightning wrote:Mr. dcrane. .. I'm curious. How much experience do you have burning coal?


More then some and less then others ;)
dcrane
 
Hand Fed Coal Stove: Crane 404


Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: coalkirk On: Sat Mar 09, 2013 5:37 pm

Wow, that was quite a wordy explanation of dampers. I would just say that both are draft limiting devices. One is dynamic (baro) and adjusts automatically as conditons change and one requires manual adjustment when conditions change.
coalkirk
 
Stoker Coal Boiler: Harman VF3000
Coal Size/Type: antrhcite/rice coal

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Richard S. On: Sat Mar 09, 2013 5:50 pm

coalkirk wrote: One is dynamic (baro) and adjusts automatically as conditons change and one requires manual adjustment when conditions change.


The manual can restrict the draft which is important if you for example you have a old stove where the draft cannot adequately be controlled by the adjustments on the stove.
Richard S.
 
Stoker Coal Boiler: Van Wert VA1200
Coal Size/Type: Buckwheat/Anthracite

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: dcrane On: Sat Mar 09, 2013 5:55 pm

they are for two completely separate purposes (Is a frying pan better then a ball point pen?)
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: coalkirk On: Sat Mar 09, 2013 10:09 pm

Richard S. wrote:
coalkirk wrote: One is dynamic (baro) and adjusts automatically as conditons change and one requires manual adjustment when conditions change.


The manual can restrict the draft which is important if you for example you have a old stove where the draft cannot adequately be controlled by the adjustments on the stove.


Yes I agree. It restricts the draft. Hence a draft limiting device.

dcrane wrote:they are for two completely separate purposes (Is a frying pan better then a ball point pen?)


I don't know what in the hell you are talking about. :lol: Frying pan and ball pont pen? I'll type it slower this time so maybe you can follow it better. Manual and barometric dampers BOTH are draft limiting devices. They do the same thing but they accomplish it differently. A baro limits draft by allowing room air to be drawn in the vent pipe. A manual damper limits draft by partially blocking the vent pipe. Both limit draft.
coalkirk
 
Stoker Coal Boiler: Harman VF3000
Coal Size/Type: antrhcite/rice coal

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Wood'nCoal On: Sat Mar 09, 2013 10:32 pm

coalkirk wrote: Manual and barometric dampers BOTH are draft limiting devices. They do the same thing but they accomplish it differently. A baro limits draft by allowing room air to be drawn in the vent pipe. A manual damper limits draft by partially blocking the vent pipe. Both limit draft.


Sounds like a reasonable explanation.
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: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: dcrane On: Sat Mar 09, 2013 11:16 pm

Wood'nCoal wrote:
coalkirk wrote: Manual and barometric dampers BOTH are draft limiting devices. They do the same thing but they accomplish it differently. A baro limits draft by allowing room air to be drawn in the vent pipe. A manual damper limits draft by partially blocking the vent pipe. Both limit draft.


Sounds like a reasonable explanation.


ones purpose is to save coal the others purpose is to save heat (two different purposes altogether!)
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Lightning On: Sun Mar 10, 2013 5:47 am

dcrane wrote:ones purpose is to save coal the others purpose is to save heat (two different purposes altogether!)

I hate to do this to ya partner but posting erroneous or misguided information for newbies to digest is reckless and irresponsible. Thats why I asked you about your experience. Your novice assumptions and misguided understanding about much of what you put into the first post of this thread is really showing your lack of experience. The physics behind your explanations don't work..

dcrane wrote:The purpose of a manual damper is to control the heat output of your stove ; when your to hot you open the manual damper thereby releasing that heat out the chimney.

This is false... Your primary air controls on the stove control the heat output.. Opening the manual damper would only release heat up the chimney if you have the load door open at the same time. Heat going up the chimney has to have something coming in to replace it, or it ain't going anywhere..

The analogies of tobacco pipes and drill bits make things complicated. Its all so much simpler than that.

dcrane wrote:#1 a baro does take a very small percentage of the heated room air and allow it to get sucked up the chimney and out of the house,

But the problem is that the air going in the baro and up the chimney must be replaced, which causes cold air infiltration from outside..

#2 is OK

dcrane wrote:#3 you now have another piece of equipment that you need to keep clean and maintain

The only maintenance needed to the baro is to clean fly ash off the backside of the baro door..

dcrane wrote:So… the times a Baro is in place and in use should be when you have a good drafting chimney and as such it can only be concluded that the use of a Baro can save you up to 50% of your fuel per year because without it you are still sucking on that tobacco pipe and all your suction is going to go directly at the bowl of that pipe unless you relieve that pressure by drilling a hole in the stem or opening your mouth a lilttle to draw air from someplace else (like a Baro allows).


Oh geez.. 50% ?? Totally out in left feild here... Your missing the purpose of the baro.. I'll get to that shortly..

dcrane wrote:It is certainly possible to use your draft controls and a manual damper to attempt to gain some coal savings or better described: to gain more heat from each ton of coal you do burn, but to do this with the sort of 24/7 efficiency of a Baro would require you to literally stand next to your stove all day and night 24/7 with one hand on the manual damper and one hand on the draft control.

Many people use only MPDs on their set up. Its efficient and they don't babysit the stove. I don't know why I'm wasting my time on this.. I'm tired..

dcrane wrote:ones purpose is to save coal the others purpose is to save heat (two different purposes altogether!)

And this statement sums up that you don't understand the physics of whats going on in the whole scheme of things..

Sigh :( Baros and MPDs do have the same purpose. They both lower the strength of the pull of a strong drafting chimney.. Saving heat and coal would be a "side effect" benifit ONLY under the condition that the stove is leaky and alot of air is getting in that ISN'T being used for combustion and its carrying heat up the chimney.

As stated by others, the MPD restricts exhaust going up the chimney.. This keeps the negative pressure in the stove from becoming excessive. An excessive negative pressure will cause more combustion air to be pulled in thru the primary air control. Which of course will make it run hotter. An excessive negative pressure could also cause more air to leak in wherever there isn't a good seal, such as around a load door. This "extra" air infilration would be heated and would go up the chimney, robbing Btus from the stove..

The baro also keeps the negative pressure in the stove from becoming excessive. But does it a different way. The pull of the chimney is "shared" by the stove and baro. The baro satisfies the pull of the chimney by letting room air into it. By doing this the negative pressure in the stove is regulated..

The beauty of a baro is that is "regulates" the negative pressure in the stove. This regulation of negative pressure means that a consistent amount combustion air will be pulled in. This translates into a consistent heat output of the stove over the burn time..
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut/Stove Size Mix

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: dcrane On: Sun Mar 10, 2013 6:05 am

I should ask the question "why do you use a MPD"? Your answer should be to control the heat of the stove (if your using it for some other purpose let me know, im all ears?)
next question... "why do you use a Baro"? ....after answering that you will then realize these items are for 2 different purposes ;)

once you realize this fact you will then also realize its like comparing ball point pens to frying pans.
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Rigar On: Sun Mar 10, 2013 7:09 am

For the sake of any newbies reading this thread....someone should make it clear that this discussion pertains to HAND FIRED burning only.....?????

...if not...we will have to start a new thread !! :D
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Richard S. On: Sun Mar 10, 2013 7:11 am

Rigar wrote:For the sake of any newbies reading this thread....someone should make it clear that this discussion pertains to HAND FIRED burning only.....?????

...if not...we will have to start a new thread !! :D


Correct, only a baro on stoker.
Richard S.
 
Stoker Coal Boiler: Van Wert VA1200
Coal Size/Type: Buckwheat/Anthracite

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: Rigar On: Sun Mar 10, 2013 7:16 am

thankyou Richard...

... I get concerned someone could read these types of discussions and try putting an MPD on a stoker
....BAD idea
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: How Barometric Dampers Function, Why use a Barometric Damper

PostBy: lsayre On: Sun Mar 10, 2013 7:51 am

Richard S. wrote:
Rigar wrote:For the sake of any newbies reading this thread....someone should make it clear that this discussion pertains to HAND FIRED burning only.....?????

...if not...we will have to start a new thread !! :D


Correct, only a baro on stoker.


What about the case of the AA and AHS Anthratube type stokers, which stoke via electronic ashing, and are otherwise somewhat similar to hopper equipped hand fired units in their basic functioning (sans for the draft inducing fan)?

My chimney doesn't draft enough on its own to warrant an MPD even if it was permitted, but I figured I'd ask this anyway. My baro damper only opens when it is extremely cold outside, and/or if there is a wind of more than 5 MPH (7 MPH seems to do it) blowing across the top of the chimney. Far and away mostly it is wind causing it to open.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13 KW)