Hi dolphinman, welcome to the forum.
What model power vent is it? If it is a Field Controls SWG 4HD stainless steel model that is OK. You have to remove the sense tube and the damper but it will work OK.
If it is a standard carbon steel unit you should not use it for coal. Although I have a SWG 5HD carbon steel unit that I use in the garage. Since it is bigger (5" VS 4") I figure I have a little safety factor. I would not use this unit for any living space though.