Question: I have a Colebrookdale stove The model is a Darby with a model # 98392 This is a wood and coal burning stove. The flue outlet is 8" diameter I would prefer to only use wood and not coal Can a 6" flue be used for burning wood? Similar sized wood stove recommend a 6" flue Answer: No, that stove needs an 8" flue due mostly to the large door opening size. It will almost surely smoke out the doors when loading if you use a 6" flue. As far as flue size for different fuels, it's the opposite of what you assume. Coal generally needs a smaller flue, since it does not smoke and it sends less heat up the flue. A smaller flue stays warmer and therefore is more likely to maintain a draft since coal puts less heat up the stack than wood. Although the 6" flue can handle the BTU's of the stove, it cannot sweep such a large flue opening clear of smoke.