Coal bed depth ranges

“There are ideal depth ranges for the size of the coal being burned in naturally aspirated stoves.” -Sunny Boy

Was reading some old threads Comfortmax Instructions Deficient in the Coal Burning Dept. and came across this statement.

Would anyone care to elaborate on the depths of coal beds that certain size coal tends to prefer?

Each size coal has a minimum depth at which it will burn so that the fuel bed won't be prone to developing dead spots. A fire with dead spots is an inefficient fire because now oxygen has a way thru the fuel bed without being used. Too shallow also makes the fire weak with a potential of dying if not thickened up.

Then at other end of the spectrum, too deep could create too much resistance for combustion air flow thru the fuel bed.

In my experience, it's pretty much impossible to have a fuel bed that is too thick with stove size coal. I've built them 16-18 inches deep.

Your draft strength will dictate how deep you can build your fire without it impeding your heat output potential.

Thanks Lee.

I should have rephrased the question to include minimum and maximum coal bed measurements. I’m sure some stove makers or someone else out there has this information figured out already.

I don't think there are really any "hard" figures for coal bed depth. Much of it is subjective by the operator. The design of the stove would have impact on the"best" coal bed depth as well as the draft strength. If you have a chimney that'll pull a -.15"wc you could probably run a pea size bed 12 inches deep and get a lot of heat lol...

Would be interested if anyone has some engineering math on this they could post.
The grate gap sizing would also be a consideration.

My Hitzer 82FA is 13" deep and they recommend nut.

i dont think the stove will really allow it to be too deep... if using the correct size coal for the stove and filling full (mounded to top of fire brick). i have stuffed over 100lbs into my gibraltar and she loves it.