Hello. I have been running a DF520 since last January for my 3700 sq. foot house and have switched to Blaschak coal this month of December, so I found that the coal quality improved and I was able to lower my feed rate from 9 to 6; however, i am using more coal now than i was before to keep the house 2 degrees less-warm (i had the thermostat at 68 last winter and have it at 66 now). For example, last January on a day when the temps ranged from 9-27, i added 5 bags to the hopper. The day before yesterday, when the temps ranged from 9-28, i added 7 bags to the hopper. Andi have been consistently using 6-7 bags a day all December when last year, the most i added in one day was 5 bags, on the coldest days. Now, logic tells me that i should be using less coal at a lower feed rate, not more. The coal i used last year was of an unknown brand, bagged by the coal guy. I never weighed a bag, but he said they were 40 lb. bags. Even if they were 40+ lbs, even 50, that's 250 lbs. a day last year compared to 7 x 40 lbs. now. So, the stoker is running longer, a lot longer if all these bags have been 40 lbs., but i should be using less coal not more! Does anyone have any suggestions? I could increase the feed rate, but then i'd go back to having unburnt coal in the ashcan and that's wasteful in another way.