Some 15 years ago we had a flue inserted in our old coal fire chimney, as it was deemed too costly to re-point the brickwork due to its age (18th century).
We were told at the time not to burn wood, only coal, but it that an exact science, or is it ok to use wood as a fuel (it's a lot cheaper!)?
Any advice much appreciated.
If you wished to comply with current BRegs the flue liner would need to be 200mm diameter for an open fire. If you are going to burn wood the fire will need a lot more air therefore a larger flue.
Assuming the lining material is SS I suggest you try burning wood and if the flue is not big enough the fire will fill the room with smoke. If you are going to burn wood regularly the flue will need sweeping 2x a year.