jpg wrote: ↑Mon. Nov. 26, 2018 8:58 pm
Thanks Paul.
That was very clear. So when people talk about "banking" the fire so that it stays alive for a long time, what does that mean in a stove like this? Do I just do what you said above and nearly close the air intake? From what I've read, folks bury all but a corner of the fire with fresh coal, and then nearly close the air intake.
I very much appreciate your taking the time to tutor me on this.
Thanks,
-jpg
Banking can mean different techniques to different stove owners because of all the different shapes and sizes of stoves. But with most coal stoves it's putting a blanket of ash over the firebed top and leaving small openings for it to slowly burn through. However, with your small firebox that risks stalling the draft which will slowly kill the fire.
My Glenwood range is at the small end of sizes. So, (pun intended) I'm in the same boat as you. What I do to get the longest burn times is "stuff the firebed", and not bank it with ash.
To start getting the stove ready for the night I open the primary and MPD to get the firebed going strongly. Then I shake ash, empty the ash pan, as I'm also adding layers of fresh coal to eventually fill the firebox right up to the top plates.
Some might think this is a big no-no because getting the firebed right up against the top plates of a cook stove will warp them. That's very true,....during the day,.... when the firebed is running hotter. But at night I close the dampers down to just the primary being open a sliver so I can just barely see a glow coming from the ash pan area. The direct draft damper is closed to the oven position so that the exhaust is going through the oven flues to extract heat and help lower the draft strength, and I close the MPD fully. And the top layer of coal being up against the top plates over the firebox won't burn until the firebed burns down enough to let the level drop. So that top layer of coal actually shields the plates from the higher temp lower down in the firebed.
That all combines to idle the firebed down so that the top plates stay at about 550 - 650 F degrees. No danger of warping them at those temps, and the firebed has the maximum amount of fuel for the longest burn. Plus all that extra depth of coal adds a bit more restriction to airflow through the firebed, thus helping slow it. When I come down in the morning, the top plates over the firebed are around 600 F, the firebed level has dropped about an inch below the top plates protecting them from the now glowing top layer of burning coal, and the stove pipe is around 110-120F about two feet up from the pipe collar.
I've done this every night for nine months of the year, now into my 14th year with this range, and not warped the plates using this "stuffing the firebed" technique.
I will add that many years ago I modified the primary damper openings to get a finer adjustment for slower idle. The primary damper is the slide type with five rectangular slots. On the two end slots I filed the edges on a very slight angle to give a tapered opening so that was the damper is closed the three middle dampers close first. Then that leaves the two end dampers with a narrow tapered opening. As the damper is closed further it leaves a smaller and smaller wedge of opening. I close the damper until 1/2 to 2/3 of each end slot is closed. This gives just enough air at both ends of the rectangular firebed to keep it all burning slowly through a 12 hour night, yet still produce enough heat to keep the kitchen warm and a 2-1/2 quart tea kettle just below a boil off on the non-firebox part of the cooktop.
So, to sum up,
1. All ash cleared until there's a healthy glow in the empty ash pan.
2. Build up the firebed to the top plates to "stuff" the firebed as much as possible.
3. Turn the primary damper down as much as possible, but not enough to choke off all primary air.
4. Oven damper set for indirect draft to extract as much heat as possible before it goes up the pipe.
5. MPD fully closed and let the exhaust go out slowly just through the gaps in and around the MPD plate.
This allows me to consistently get 12 hour burns out of a firebox that only holds about 25 pounds of nut coal and still have plenty of firebed left to make a fast recovery to refuel and shake ash each morning.
When I come downstairs in the morning I open the MPD, put the oven damper in direct draft, and open the primaries. Then I feed the cat and make a cup of instant coffee with already near boiling water from the kettle. By which time the firebed is going strongly and built up a "heat bank" in the stove and chimney so that adding cold coal won't stall the draft. I put on a layer of coal and shake ash. After it finishes popping, I set the dampers for the day. Plus, when I walk into the kitchen, the cooktop is hot enough to start cooking breakfast right away.
Don't trust to learn this at night. This works well for me partly because I have a strong drafting brick chimney that was built for a coal stove. How well it will work for you depends on your stove/chimney system drafting ability. So, try it during the day so that you can monitor it safely and be there to adjust dampers and see how the stove responds. Pop a hatch, or a port or two, and don't be afraid the see at what point of damper settings the fire dies.
Keep in mind that as the outside temps vary, so will the draft strength. Therefore your damper settings will need to be opened a bit more in milder weather and closed more in colder weather.
Paul