I have a friend who has a furnace that was installed. Oil and wood fired. It spews black stinky goop out of the joints, Now i know this is caused by condesation but how to stop it. We are told to much draft not enough draft to long of a smoke pipe run and so own. From what i know and see i think its during the off cycle were the automatic damper closes and everything cools down. At that time it condensates and then makes the black stuff. Help
Please.
Please.