This example is for a relatively air tight stove. Focus on how much air is coming thru the primary combustion air opening for minute. For a higher volume of flue gases to exit the stove, what would need to happen at the primary air opening? Answer, more air would need to come thru it. Then ask yourself, how can more air volume come thru the primary air opening? Only two ways.. We can open it more OR we can increase the negative pressure in the fire box.. What I'm getting at is that the volume of gases leaving the stove are dictated by the volume of air that is entering the stove. The volume of air that's entering the stove is dictated by the stove's negative pressure. They are all tied together, so it doesn't matter what device you use to maintain the -.04 in the firebox.joeq wrote:You stated that if 2 identical stoves had the exact same conditions, (-.04 draft) one with a baro and one with a fully closed MPD, they'ld both be emitting the same amount/volume of gases. I'm not understanding. I do understand the closed MPD still allows air to pass, but with such a restriction, how could it possibly be equal? In volume?
No way!!joeq wrote:Would you rather be outside, shoveling snow? Cleaning your garage? Doing homework?
Lightning wrote: What I'm getting at is that the volume of gases leaving the stove are dictated by the volume of air that is entering the stove. The volume of air that's entering the stove is dictated by the stove's negative pressure. They are all tied together, so it doesn't matter what device you use to maintain the -.04 in the firebox.
[/quote]KLook wrote:If you wanted more heat and the baro is set for the correct draft, all you had to do is open the damn MPD all the way up and increase the AIR in!.
Well yeah but then the mano reading will fall.. The same thing would happen if you prop open the baro door.. The mano reading would fall.. In both cases less volume will leave the stove...joeq wrote:What I'm asking is if both stoves have the same primary air opening, and both are up to temp with a strong flow maintaining an -.04 draft, and then on one stove, you "slam" the MPD shut, wouldn't it have to slowdown and restrict the airflow from that stove? Strictly speaking "volume" of heated air.
Here's why its burning hotter.. It's hard to keep conditions in the fire bed constant to compare one burn cycle to the next just because of variable ash clearing , coal sizing and possibly fines.joeq wrote:Especially now that my primary air is also opened more.
Guys, Just wanted to chime in with my latest observations. Being such a long time wood burner, and this being my first season with coal, making the transition has been somewhat trying. somewhat like " teaching an old dog new tricks". But thanks to this web site I'm doing ok now. However, after many hours of observation, and especially today, I will be adding a baro. I have to admit
trying to control the draft with a MPD on days like today is virtually impossible. At least for me. With the main draft closed, the idle draft closed the MPD Closed the mano bounces from .03 to .12. Just from an economic standpoint it makes sense. Seems the older I get the tougher it is to accept change. Congrats " baro boys" you converted a MPD man.
Lightning wrote: Well yeah but then the mano reading will fall.. The same thing would happen if you prop open the baro door.. The mano reading would fall.. In both cases less volume will leave the stove...
KLook wrote: It is like coming up with a carburetor that gets 100mpg.
Lets label it heat.joeq wrote:In the above scenario, the burning coals are producing a certain amount of ...power, heat, pressure. Whatever we want to label it.
So there is a baro AND MPD on the second stove?? And why would the draft remain constant, you mean the negative pressure will remain constant? I don't see how it could.. That would imply the MPD is doing nothing.. Its gotta do something..joeq wrote:If the combustion pressures are equal in both stoves, but one of the stoves shuts the MPD, yet the draft is remaining constant, (because of the baro),
The chimney causes the negative pressure, not the coal bed.. The coal bed makes the heat, the chimney causes negative pressure to form from the heat rising out the chimney..joeq wrote:consistent pressure from the coal bed.
You have the baro after the MPD correct? Heres the dilemma.. Too many things going on at once Look at it this way... the baro is limiting the draft strength of the chimney, then the MPD is restricting it further to attain the -.04 you like to keep.. I have mine set up the other way but this is considered a reckless arrangement since having a blockage (MPD) above the baro could (in theory) promote flue gases to leak out the baro under the right conditions.. Truth is, during times of excessive draft, I'll tweak my MPD so the baro will do its job better.. I don't recommend this arrangement though.. It's potentially dangerous I guess. I only use the MPD when I need to. The better arrangement is an over sized baro which I plan to do for next year.joeq wrote:When I close the MPD, the baro door should close to compensate. (I'm so confused)
joeq wrote:Figured this title would bring in all the Sheldon Cooper fans. (Big bang theory).
Was curious about the theory or opinions on this. Concerning draft and/or rising heat out of our stoves. The more air flowing through the coal bed, usually dictates the intensity of the fire. More air equals more heat. (Providing enuff fuel to support it). Air in usually also requires air out. I've been skooled here that, if we close down our MPD, then more heat will be retained into the stove. (Makes sense to me). However, if closing the MPD slows down the draft, then the stove can't produce the required amount of heat to build the fire. I'm wondering about which phenomenon has a larger potential for heat output. Close down the MPD, to retain heat, but lose the higher draft, or open the MPD for a higher draft, but send the hot air up the chimney? Which is the preferable method?