I'm pretty sure Lightning was referring to me So here is all I am going to say on it. Use what suits you. But, do not mistake your opinion or your assumptions on reality. It was -9 here this morning. It is 1 degree here now. I heat a 2400 square foot home, built in 1970 with no upgrades, on 65-70 pounds of coal a day. My thermostat says 83 degrees right now. My electric bill last month was $56. This month is going to be even cheaper. I type this in a pair of gym shorts in the upstairs of my home. The stove is in the basement. I'll put another 5 gallon bucket of coal in my stove around 9 pm tonight. When your stove with the baro thingy does that as efficiently as mine is dong it, I'll listen. Make no mistake though, after your post stating your position, I'll never coin you as a genius, sarcastically or not.
I wasn't being a smart guy on my first post. But, the genius term you coined me with might suit me in the home heating department because, a MPD and controlled air intake in the form of a stove draft, works real well in my case. Much better than a baro thing. :^)
And when we get some rare and odd atmospheric condition that causes your chimney to loose draft and because you have manually choked your stove pipe down to the size of a 2 inch PVC pipe, you will be the first to tell us about it? IF you survive that is....
Even though wood and coal are different, wood is relevant here because it has a higher stack temp which should induce better draft. I cannot tell you how many people I have known that had their house get all stinky with wood smoke because conditions changed and they were not around to change the mpd or if they were, it is to late when you smell it. Strong stuff. Move that thought over to coal with a lower stack temp and no smoke but fumes that will kill you and tell me why you want to block a flue pipe that is engineered to guarantee your survival? I have a son and family living in my house in Maine, and there is NO mpd in the flue pipe. You are taking chances trying to squeeze the Nth degree of heat out of the already cheapest fuel going. Yes you can, but you take your chances. Why not just put up a 3 inch metal chimney to save money? Maybe some of the terra cotta drainage tiles that are 4 inches in diameter? Cast iron sounds perfect, building inspector will think it is a stink pipe.
I understand not wanting a baro for wood, even though my brother and others are using them in carefully setup systems, and I would if I ever (never) burned wood again. But to have a device that maintains the perfect draft in most situations and not use it is foolish. And then there are those manufactures that don't want anything used. We call them lawyered up, but there is a reason for that probably.
I know this little diatribe wont change any minds, but that is not the point. It is coming from a guy that would use a baro for wood!
Like FFred, I trust my experience and working knowledge just like you guys choking the piss out of a correct size pipe with a butterfly valve!!
May the discussion continue........