Thank you for the response! I have not been able to successfully carry a coal fire, it appears to go out, and I have gray ashy coals that don't appear to have burned. I've only attempted to start a coal fire when it's been cold out, below 45 degrees F. I originally was told the 8 inch flue was probably too big, not creating enough draft to keep the coal fire burning, so I did convert to a 6 inch flue and lined chimney in the Fall. My draft control greatly improved for burning wood. I tried coal a few times, but not successfully so I gave up.
My local dealer has Blaschak anthracite from PA. I usually get the large chunks so it doesn't slip through the grates. I have tried to add the coal to the fire after I start a good wood fire and have a good bed of red hot coals. I've watched numerous videos online, and have tried to get the ideal blue flame, which I've done once, but could not keep the fire going. It went out. I'd love to master this.
I'm wondering if I might have air leaks in the stove causing the issue? I've put new gaskets on my stove within the last year. But, maybe elsewhere I'm letting too much air into the stove? I'm going to inspect this and chalk as needed, but haven't gotten to this yet. Again, thanks for your time and response. Any info is good info!
When a wood fire burns down to coals, the chimney is cooling and not drafting at its strongest. The least amount of wood that has burned down the better.
Start with paper, cardboard, and small kindling on grate. Sprinkle a little coal on it. Kindling should be small splits that will burn freely with little smoke. You want ripping flames to go up through the coal. Light it, and if not burning hard, crack ash pan door. Add a little more coal on top to keep flames going up through it like a torch. The edges of coal will start to glow, and by the time flames die down, coal should be started. Keep adding coal with a sprinkle from shovel across top. Lots of air until coal mass is glowing, with blue flames. It takes lots more air than wood to get it going. A wood coal bed will not allow enough air up through it. You want the coal down on the grate for good airflow up through it.
The larger the pieces, the more air between them, and the faster it will burn. All sizes has the same BTU content per pound. Smaller pieces get less air, burning slower for warmer days. That is when you load with fines around the bottom of bin. Chestnut should not fall through.
Old Company Lehigh was the best. I believe that breaker was closed long ago. Reading is my go to now. Tried Blaschak, had more unburned pieces, more ash, and tore up my stainless cap every year. That was burning in a Hitzer, EZ Flow with hopper. Results vary with stove designs.
After the initial heat in chimney from wood comes down, stack temperature will be about half that of wood. You may think the stove has stalled for a few hours as the entire fuel load ignites over time. Coal is very slow to respond, unlike wood.