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
). 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
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.
