Question: My Dad has bought a used woodstove to put in his basement beside his oil furnace to use in case there is a power failure. What are your recommendations to this installation? Should the woodstove connection be above or below the oil furnace connection to the chimney? The oil furnace is on it's on 6" or 8" diameter flue. Answer: The stove should be installed below the oil furnace. Most experts recomend that each usint use a separate chimney, and this is the best way to go. I assume since it's for a power failure that both will not be used at the same time.