UPDATE After one full week of burning, I consumed about 500# of coal, but this should have been less, since I still have a problem with unburnt coal in my ashpan.
I started on last monday night, seven days ago, with a full coal hopper. I left Tuesday morning for a five day assignment at work. I had my caretaker keep track of the weight of the coal added to keep the hopper full, and to keep an eye on the ash pan. The coal use was on average about 80# per 24 hour period, but the ash pan was about 80% unburnt or partially burnt coal... %%$%$^$&* !!
So when I got home on Saturday afternoon I looked at the ashpan, and sure enough the report was right, there was a significant amount of fresh shiney coal and a lot of partially burnt coal in with the ashes. The ashes were everything from small golfball sized clinkers, very soft and fragile, an a lot of fine ashes, like powder.
I thought about HOW fresh unburnt coal could make it's way through the firepot, and the only idea I came up with was that the firepot was not burning all the way around, there had to be a portion of the coal bed that I could not see that was not burning, and the shaking action of the ash drawer/grate was pulling this fresh coal from the bottom of the coal bed as it was replaced on the top by fresh coal.
So I stopped the auger from feeding fresh coal and let the fire burn down several inches, and I did see some areas that were not burning as hot as the others.. Then I did the cardinal sin with a coal bed.. I got a poker and stired the hot coal bed, moving the hot coal all around, to get the fire burning all through the firepot... or so I thought.. I started up the auger again and an hour later looked at the fire, it appeared to be burning all the way around... and I went to bed..
On Sunday morning I awoke to a cooling house.. The boiler water was down to 65* and the fire was out... Lots of fresh shiny unburnt coal in the firepot, and no fire..
So I reached in through the inspection port and pulled all the fresh new coal out and only 3-4" down found solid ashes with coal mixed in.. Aparently when I stirred the fire I upset and closed off the remaining air passageways through the ashes to the fire ... So the fire went out
I found as I dug out the ashes that there was a lot of big clinker in the ash, I think this was from the previous week when for five days the fire sat and burned while I was gone and the motor had failed. I think that as the fire burned down the clinker was formed around the central core of the remaining fire. When I replaced the motor, and found the fire still alive, I just let the boiler start up again, not thinking that any problems existed in the ashes.
I had turned down the anthrastat to hopefully make the coal burn more completely, but this caused the ash to deepen and eventually make the fire very shallow, and fragile, my stirring the fire was all it took to kill the fire.
I completely cleaned out the firepot and the ashdrawer, and started over again with a fresh fire, and fresh coal.. I imediately noticed that I had higher flue temps than before, I can see over 300* after a 10-15 minute burn, before the highest I saw was 250*..So I do think I did have a partial fire in the fire pot.
But two days later, I still have lots of unburnt coal in the ashpan.. so I called a coal boiler service person that a fellow forum member had given me then phone number for. I learned that the AA 260M boiler often has a lot of unburnt coal in the ashes when the weather is warm, and that I may have to live with this untill the cold weather really sets in... The firepot holds a lot of coal and the short time that the fan runs is not enough to get a full burn in the coal.
But I can adjust the aquastat to have a slightly higher temp and make the temp differential higher, I had it at 10*, I adjusted it up to 20*, so the fan should run longer and maybe burn the coal more completely. I will adjust the anthrastat to near the factory setting and see what transpires..
The coal consumption I am burning or using is pretty low, should work out to about one ton a month at the current temperatures and weather. If I double this for the three really cold months of Dec. Jan. and February, then my winter consumption should be around 7-8 tons.. less than half what I burnt last year.. not bad, and if I do manage to get the boiler to burn all the coal then I should burn even less...
So I'm still learning, and experimenting, I hope to cure or significantly reduce the unburnt coal issue soon.