this is a very descriptive and informative diagram. Look closely and you'll see, in terms of efficiency, perhaps the emperor has no clothes ? No offense to anyone who owns or restores this distinct, collectible antique stoves. Don't misunderstand me, I like the stoves.
Look closely at the baseburner design, then compare to the basic rules of thumb for ducting stove gases, from a coal stove manual below:Limit the amount of connector pipe.
Position the stove as close to the flue as possible, 8 ft. or less.
No more than two 90° elbow fittings should be used.
Any horizontal connector pipe should have at least 1/4 in. of rise per foot in length.
I can see at least (3) 90 degree angles, and a 180 degree loop, in the baseburner passages. If the last vertical upward run had to turn 90 degrees to go into a horizontal wall flue pipe, then that's (4) 90 degree bends. There is one vertical downward run, and 2 horizontal runs, with no rise at all, or negative rise, it goes straight down, instead of up. These stoves are held up as the model of efficiency, when in fact, they are anything but efficient at exhausting the spent coal gases. Proof of this is, the stove temperatures typically go DOWN when the baseburner ducts are opened.
Since when is a HEATING STOVE temp going DOWN, a sign of efficiency ? If the stove is colder, the room will also be colder. Not warmer.
The stove temps go down, because the draft is cut a noticeable amount, when the baseburner passages are opened. All those bends and curves have detrimental effects on stove drafting. The extra cast iron has a heat sink effect.
If it was truly more efficient, when the baseburner passages were opened, the stove would maintain the same temp while heating more surface area, or get even hotter, on the same load of coal and same draft intake setting. Getting cooler only shows, the draft fell off, and dropped the stove and flue temps. What heats better, a hot stove, or cooler stove, if all other settings are the same ?
Opening up the baseburner vents and the stove dropping in temp, is a sign of DECREASED EFFICIENCY, not increased efficiency. The stove is putting out less heat with the same draft opening. The main draft intake to the fire, would have to be opened further, to increase draft and get the stove back up to the temp. it was at, before the baseburner passages were opened. Requiring more air and draft to be added, to get back to the same temp, is not efficiency. That's inefficiency. The baseburner design requires burning the stove with more draft to get back to the same temp. level, because it then has more cast iron to heat up.
It probably doesn't heat any better than an Oak stove set the same draft, with an MPD closed.
And it couldn't hold a candle to today's modern, fan forced air, internally baffled, 100,000+ BTU monsters.
The baseburner design was cutting edge, for its time, when there was no widespread electricity or fans to put into a coal stove. Saying these stoves are the most efficient design today, is naïve and misleading. They aren't. Rather, they are a finely crafted, aesthetically pleasing stove, from a bygone era- a fine relic of the past. I hate to say this, because I really admire these old stoves, but the design is a gimmick by today's standards.
If someone suggested you run the stovepipe out of your stove, then straight down at a 90 degree angle, then at another 90 degree angle into a horizontal 180 degree loop, then straight up again at a 90 degree angle, would you do it ? Most likely you'd think the guy saying that was nuts. Any stove company that made such a thing today, would be laughed out of the market. Any installer who tried to put stovepipe in a home like that today, would probably be fined or sued for breaking code laws.
I've seen one stove with a downward angled stovepipe, that then connected to the vertical wall flue pipe. To date that is the lousiest burning stove I've ever seen, it won't hold a coal fire, and barely holds a wood fire. It smokes into the house on a regular basis. It belongs to a relative, and when we come home from that house, we have to wash all our clothes, because the clothing and coats smell like wood smoke in a bad way.
Hot air prefers to rise, not go downward and horizontal in bends like a pretzel. Elsewhere on this board, there is a post by someone who tried a baseburner with wood, and it kept backdrafting smoke into the house. That is understandable considering the bends in the stove passages. If a stove can't burn wood, it sure as heck won't burn coal. Wood is actually easier to burn, and will burn with less draft- it has a lower ignition temperature.
How many people do you know, who have been actually heating their homes for the past, say, 20 years with a baseburner every winter, locked into baseburner mode ? I don't know a single one. But I do see a lot of them for sale, at dubious prices. There's quite a few sitting in corners not connected to pipes and not working, but all chromed up, with electric lights in the firebox windows.
What's that say ?
I'm sure many of these stoves work well, but only if they are connected to some wicked draft to overcome the slowdown created by the baseburner passage bends in the design. If the design is just heating more metal but the stove temp is going down, that's less heat in the house and room, not more heat.