How Much Coal Is Wasted Per Day Through a Barometric Damper?

The proponents of MPD's over Barometric Dampers often state that they have gone the MPD route because they would lose too much heat out the chimney if they had a barometric damper. A lot of people use barometric dampers. How much more coal are they foolishly burning per day vs. those with manual pipe dampers?

Very difficult to quantify but less than they would waste without one if they have excessive draft in their chimney.

It breaks the draft or if you will, It stops excessive draft from pulling through the stove, thus its saving fuel, not wasting it.

Also by doing this it keeps superheated air in the stove longer, allowing it to be radiated into the room.

What is lost is a little warm air from the room, but its minimal compared to the gain of a constant draft through the stove rather than excessive. ( Just cover one up with foil and watch the stack temps rise, now you have a lot of heat going up the chimney and its burning more coal to.)

This is misunderstood by many, its just hard to wrap your head around it, but it works, obviously better in some set ups than others. Manual pipe dampers work to, just on a different principal, they restrict the flow and they are Manual and thus need to be adjusted from time to time, the barometric adjusts itself.

Bk

Oh dear... Here we are at the MPD vs Baro argument

I agree some room air does go up the chimney with a baro as where no room air is lost with a MPD. This room air causes cold air infiltration from outside. Its difficult to justify how much goes thru the baro door. The million dollar question, How much of a percentage it amounts to when compared to the total air infiltration that a house already has. The baro is a valid cause of cold air infiltration but is it enough to discount a baro?? This is the shade of grey in my opinion..

I've noticed that for me, the manual damper doesn't hold a set pressure as flat as a barometric. My heat output still tended to yoyo, and I was still constantly tinkering with my primary air control to even It out. How much coal was I wasting by heating the stove more than it needed to and does it equal what I saved in coal when it wasn't heating enough?

I believe a coal fire makes best use of the available oxygen when it isn't constantly flared and then let to cool down but instead its allowed to burn with a constant oxygen supply. A baro helps aid with this consistent burn. I see it when I'm monitoring my temps thru the burn cycle.. After initial burn off of volatiles, the temp will fall (after closing the load door) then over the course of about 3 hours, the temps will increase about 5%, then plateau and stay there till tending time again. During that 3 hours, the draft pressure is a steady -.03, primary air is untouched but temp grows.. What's the only conclusion? More of the available oxygen is being used. This is very important. Our atmosphere is 80 percent nitrogen. That means 80 percent of the air going in is just there to carry heat out the chimney. The more of the available oxygen that can be used means more heat output per loss of heat due to nitrogen carrying heat out the chimney and those ratios are huge

If I had to pick one or the other, that MPD would be on its way to the scrap yard at $.08/pound.. Since I think the benefits of an even draft outweigh air infiltration caused by the baro. Buts that's just my opinion and its hard to prove.

Truth is there are many variables and its difficult to justify if the overall effects of one trump the overall effects of the other. I think that's why everyone is so passionate about which one they choose and for what reasons. Me, I use both to maximize the benefits of each. I think MPD and Baro get along just fine on the same pipe

I'm intrigued with the science involved with operating a hand fed. I'm so glad I didn't start with a stoker hahaha

bksaun wrote:
What is lost is a little warm air from the room, but its minimal compared to the gain of a constant draft through the stove rather than excessive. ( Just cover one up with foil and watch the stack temps rise, now you have a lot of heat going up the chimney and its burning more coal to.)

This is misunderstood by many, its just hard to wrap your head around it, but it works, obviously better in some set ups than others. Manual pipe dampers work to, just on a different principal, they restrict the flow and they are Manual and thus need to be adjusted from time to time, the barometric adjusts itself.

Bk

Basically I agree. If your talking about stack temperature after the Baro going up when you cover it with foil that is mostly due to no more cooler air entering the stream as well as increasing the air flow through the bed. If your talking about stack temperature going up before the Baro, that is due 100% to the hotter burn caused by increased air flow through the bed when you put foil on the Baro.

There was a guy in Chicago in the mid 1980's that sold "magic boxes" that attached to the flue piping on boilers. These are boilers that are in the 250k+ BTU range. Not your average homeowner boiler. Almost every place in Chicago burned natural gas and once set up and dialed in the burners were virtually never touched again. The flue gas composition was checked once a year and some minor tweaking took place but not much more than that. These "magic boxes" were square sheet metal boxes that stood on all-thread legs on each corner. They had two baffles that would make the flue gas first go down and around the first baffel then go up and over the second baffle and then exit the magic box to the normal flue piping.

The installer would take flue temperature readings before installing his "magic" box and again after installing his "magic" box. The after the box temperatures were dramatically lower. He claimed his box with the baffles slowed down the gases leaving the boiler thereby increasing it's efficiency and saving the customer fuel. Neat Huh? Convinced a lot of people. This guy sold a lot of his "magic boxes."

The box was open at the bottom. It did lower the flue gas temperature as advertised but had no effect on the fuel usage. All it did was pull cooler room air in the open bottom dropping the temp of the flue gas. His silver tongue and the hopes and dreams of the owners saving money did the rest. He was finally tracked down and prosecuted for false advertising, misrepresentation, and a bunch of other fraud type charges.

Simply put pure plain and simple,,,, baro's are for automatically minimizing excessive draft in a chimney. MPD's are for assisting the regulation of air going through the furnace/stove/boiler/ etc.

DISCLAIMER BEFORE THE FIRESTORM STARTS>>>> use of Baro's and/or MPD's are unique to every installation and there is no hard and set in concrete rule on the use of, or lack of use thereof, in any fuel burning device.

Rev. Larry

it's my experiance ...after rebuilding many many free standing stoves, yes and some stokers most damage comes from to strong a draft having one is good,but setting it proper,is the key,usually the lighter the better .02 to.05 ,if you can find an outside air source even(save room air) better. It is a coal saver and a stove saver

Lightning wrote:Oh dear... Here we are at the MPD vs Baro argument

Yeah, we're never all going to agree on this question. Use what you prefer. But a manual damper and a barometric damper do the same thing. The barometric damper just does it dynamically with changing conditons. Only the very lucky among us have the luxuary of getting to sit by their stoves all day long. For those lucky few they can adjust the manual damper as wind and other conditons change. For the rest of us poor bastards, we have to rely on a barometric damper than can adjust automatically. I know my boiler uses less coal with a baro and my stack temps are lower.

bksaun wrote:It breaks the draft or if you will, It stops excessive draft from pulling through the stove, thus its saving fuel, not wasting it.

Also by doing this it keeps superheated air in the stove longer, allowing it to be radiated into the room.

What is lost is a little warm air from the room, but its minimal compared to the gain of a constant draft through the stove rather than excessive. ( Just cover one up with foil and watch the stack temps rise, now you have a lot of heat going up the chimney and its burning more coal to.)

This is misunderstood by many, its just hard to wrap your head around it, but it works, obviously better in some set ups than others. Manual pipe dampers work to, just on a different principal, they restrict the flow and they are Manual and thus need to be adjusted from time to time, the barometric adjusts itself.

Bk

Exactly! Well said.

I compare the two devises this way, I have a hole in my gas tank but the gas only leaks out when I drive up hill. The mpd is the hills and the baro is level ground. I now I have a leak but I also drive better! just my $.02.

To efficiently burn X amount of coal in X amount of time requires X amount of air. Only one way to do that. Keep the X amount of air supplied to the stove constant. Provide a measurable constant amount of draft,...AKA, air supply = Baro.

To complicate it further if the stove has a bi metal controlled air inlet the use of any damper is probably not necessary except in cases of extreme draft. The bi metal thermostat will compensate for draft change.

I read that some EPA certified wood burning stove instructions specifically forbid the use of any type of pipe damper. It either can fry the catalytic converter or change temperatures in secondary burn chambers reducing efficiency and increasing pollutants.

Depends........ If you have a SUPER draft, it SAVES, not wastes. The type of equipment is one of the biggest factors, also. My brain hurts with all this information challenging logic. Larry, you sure make us think, and question our opinions.

Thanks Whistlenut!

There are other active baro vs. MPD discussions feuding over the merits of each. With this thread I'm only trying to solve the dilemma of how much coal is being wasted daily (monthly, etc...) by the use of a barometric damper as opposed to the use of an MPD. I'm not trying to promote or fault either one here. I'm only trying to find out if there is any real merit in the assumption that a barometric damper lets a noticeable amount of heat out of the room, thereby requiring some measurable quantity of extra coal to be burned to compensate for the lost heat. And if there is a measurable amount of additional coal required for the users of barometric dampers, what is this measure?

I understand, and you sure keep us thinking. It promotes good logical responses. I like it. 12 degrees here, 3" on the ground and snowing steadily....and the storm isn't even close yet.