cannot keep fire buning

I know the answer to this question has to be here somewhere, so forgive me for bringing it up again. I am new to coal burning. I am burning deep-mined nut coal in my Gibraltor coal stove. I can not keep my coal fire burning longer than 4 or five hours without attention. It doesn't matter if I keep the damper open or closed the fire goes out. I only keep about 3 to 4 inches of coal in the box at a time. Perhaps I need more. The fire bricks are about 4 inches higher than the coal. As the fire goes out there are patches of darkness where there is just ash mixed with unburnt chips of coal. Also I was wondering as I close the damper, what is a healthy coal fire supposed to look like if I expect it to burn for about 8 hours? Should all the coal be glowing red, or should the tops of the coal nuggets be black with a bright orange bed underneath?
There seems to be a lot of unburnt coal chips mixed in with the ash. Is this common?
Thanks for any help,
Sean

It is very difficult to tend an anthracite fire that is too thin, once you get it going fill the firebox to the top of the firebrick. Running a smaller fire will not save you any coal and it will provide you with a lot of grief, fill it up. What you describe is exactly what I find when I run my firebox to low, a dying fire, unburned coal and more work. Here is a little info that may help.

http://www.homewarmth.com/pdffiles/coalburningtips.pdf

I had the same problem for almost 2 years. First: Is all of the coal shinly and very light (weight-wise), if you got it from a mine and not from the breaker/sorting plant or a distributor it may have marginal quality pieces (the edge of the rock body that the coal vein is within will resemble the coal but will not burn well, will be heavier and dull in appearance than the good coal). If this is the case, you will be able to get a fire going, but to keep it going you will need better quality coal from the breaker or a distributor (it will be more expensive from the distributor than if you go directly to the breaker/sorting plant). I went through this process (found and mine nearby and it was a lot cheaper, but it isn't sorted to remove the marginal quality coal - makes for a lot of headaches).

With regard to the thickness of the coal bed you are burning, it should fill the stove to the top of the fire bricks. You should have more/a thicker coal in the rear of the stove than in the front (it's referred to as "banking"), you'll know when you have enough - it will be sloped from near the stove's door and the fire bricks will be covered in the rear.

The fire should be glowing red throughout once it is burning well, add the coal to your initial fire slowly in thin layers until you have it all burning/glowing red. The top of a good-burning fire will have an ashy apperance after a while and should stay that way until you increase the draft, shake and add more coal, but the bed should remain red and glowing. Remember, coal burining is not like wood burning, you must add slowly and be sure it has all "caught fire" before you add more. Throttle the draft back once it looks like it should and enjoy.

There should not be many unburnt chips in the ashpan, this may confirm my "bad coal" theory. In my opionin, the quality of the coal is as critical to maintaining a good fire as anything.