Anthracite Properities

I was wondering about some properties of anthracite coal. First off lets say I load 40 to 50 pounds of coal, how long would it burn on a low draft, and on a higher draft. I was also wondering if someone had pics of their coal stove and show the progress from when first lit to burned up. I am having problems determining when to shake down and reload. I have heard when the coal drops by 50% Thanks. I havent been able to find pics of the progress of burning coal. Maybe there is a way to tell by looking at the coal before reloading.

The length of time a 50# quantity of coal will burn has many, many variables. If in a stoker stove, it may last more than a day in warm weather, maybe even two days. It would burn just enough to keep a fire going.

In a hand load stove, a 50 # load may be only 6" deep in a large firebox, or maybe 18" deep in a small firebox. Basicly, the surface area determins heat output, and depth of coal bed determins length of burn time.

So in a small stove with say a 9"x 10" firebox, a 50# load would be about 12-16" deep, and with a very low draft setting in warm weather, this coal could last for almost a day before it is all burnt up. With a cold night, and a high draft setting, it may only last 6-8 hours.

In my big boiler, I have my firebox reduced to 15"x20", I can increase this to over 25"x20" if I need a lot of heat for very cold weather. I see about 1" of coal burnt per hour with the weather around 30*. So I get about 12 hours out of a 12" deep bed of coal.

If the weather is colder, the burn rate increases to about 1.5-2" per hour. So for me I need at least a 12" deep load for a night, and later in the season, over 20" deep for a sub-zero night.

I would try to keep your coal bed as deep as you can all the time. Once you see the bed start to burn out, I see less flame, and more 'dead' areas where the coal is not glowing red, then I would shake the fire down and add enough coal to fill the firebox. Coal likes a deep pile of fuel. It is not happy with a shallow bed of fuel.

Every stove has different characteristics. So in one stove you may see the level of the coal drop only a little in say 6 hours of burning, then drop drastically when you shake the grate. Another make of stove will have the coal ash drop through the grate as it burns, so you would see very little drop when the grate is shook.

I don't know the make or the characteristics of your stove, but I'd say just keep the firebox loaded up to the top of the firebrick lining the firebox. And keep track of how many hours results in how much coal burnt.

I can only give you generalities about your questions, but my best advice is to go ahead and start burning in your stove, and keep a few records to refer back to as the season goes on. These records will help next season as well.

Hope this helps Greg L

I didn't answer one of your questions. When you add a fresh load of anthracite to a hot bed of coals, you will only see the black coal and maybe see some wisps of steam coming up through the gaps in the coal.

You will probably hear a little crackling, not unlike the sound of a bowl of 'rice-crispies' cereal. You may smell a slight smell like a kitchen match burning, or a firecracker gone off. I find the smell pleasant, however, it's not in my house, my boiler is in an outbuilding.

Next you will see little 'ghost flames'. Little wisps of blue flame will start to show coming up through the coals. soon the whole bed of black coal will have a thin blue blanket of fire above it.

Soon the red glow from below will work it's way up through the coal, and the top layer will become red with black spots. Each lump of coal will be burning on it's edges, but the top of each lump is not burning yet, so it is still black, so it shows as a black spot with red around it.

After a few hours the black spots will be gone and the entire bed is red. At this point I would call the fire mature. Soon the lower layers will be only burnt out coal or ash. If the grates are shook at this time you would probably see a drop in the coal bed.

Later you will see areas where the red glow is less intense, and may be a low spot which is all ash. This would be a very mature fire, nearing burn-out. The ash will glow red for a long time, giving up every last bit of heat from the earlier fire.

A burnt out fire will have a few hot spots with many dark, cold areas. This fire will be hard to resurect, you may have to nurse it along with bits of wood or small coals 'till you can get a good strong bed of hot coal to load fresh coal on top of.


Hope this makes sense and helps Greg L

See, Im more used to wood. I want the wood charred but still whole then dampered down. So when anthracite is burning you want it red? Thats a mature fire then from there the burn time will vary. I have a wood coal furnace US Stove 1500 Hotblast to be specific. I feel I need more coal for a deeper bed and more draft at night. Like I said it was just hard for me to determine how far along the coal is when burning. My father never burnt anthracite, and I have more than a few times, but its still tricky for me. Soft coal im fine with, for me it burns like wood. Sometimes I burn lump coal, but I like the clean burn of anthracite. Thanks for the reply, I appreciate it.

I haven't used a a lot of hand fired stoves but most people that do get on a 12 hour schedule, they shake and load it up twice a day. The damper is set so they get the most out of the fuel available but still have enough to keep it going. You of course can get on whatever schedule you want if you have the time to tend to it more a day.

I don't have photos of all stages of a fire, but here are a few that I have in the computer right now.

I'm not sure these will help or not.

These photos represent what happens with my firebox, grates, blower and chimney. Other stoves, boilers and furnaces may look much different. This is what I've seen with both my small first boiler and my current large boiler.

Greg L

I know that draft will really affect the burn rate of the coal, but with the mature fire you have there, how long will it look like this before you have to shake and reload? Thats my problem, I think if I turn up the draft, It will eat up the coal within a few hours like wood would. Thats where I am having problems on how long a good load will go. My wood furnace will hold about 90 to 100 pounds of coal, and it will produce a bed probably 6+ inches thick.

laynes69 wrote: It will eat up the coal within a few hours like wood.

Coal lasts many more hours than wood which is one of the benefits. You don't have to be messing with it every 4 or 5 hours. I'd suggest just working your way up, try opening the draft a little bit more each day until you find out the farthest you can go. The fire you see in the second pic may look like it's ripping but that's just how it looks. the coal will turn bright red but it will stay like for a long time.

That second photo shows about a 6" deep fire, it could look the same if it was 12" deep. My firebox seems to burn about 1" per hour. So the pictured fire should burn for about 4-5 hours before it has to have more coal added.

As Richard [ The CoalMan] said, just build up a fire and take a few notes and observe what it takes to get a desired result. Every stove is different, and it will burn different with cold/warm weather where the draft is stronger/weaker.

Once you see a fully red fire, keep looking for spots getting dull or going dark, [usually 4-5 hours minimum] these spots are burning out and nothing is left in the dark spots but ash. Once the burnt out spots occur, this is the sign [for my firebox] that I need to shake and reload with fresh coal.

If I wait too long, and I have mostly ash remaining, there isn't enough hot coals remaining to start a coal fire again. I've had to take two splits of wood and use them like scoops, scoop up the remaining hot coals between then. Add kindling and create a wood fire from the coal embers... The start over again.

Just jump in, and get your feet 'wet' You'll figure it out pretty quick.


Take care, Greg L

I appreciate the help. This winter I'll give it a try when it gets down below 20 degrees. I'm anxious to see how it does. I need to get some more coal.