Im burning mostly ash,and it seems i m getting a lot of wallnut to egg size coal chunks..i get a hot fire and close the air off,i get good secondary borns,but it seems i have to sture the coals,and they just keep pileing up higher untill i shovel some out...am i burning not long enuff with the air open...loveing the stove tho..i fill at 5;30 am return at 6;30 pm and house is still 72' and a bed of coals...