I am getting ready to install my kaa-2 boiler and questions about the size of and how to mount the baro damper.
I have a clay lined 8x8 chimney that is about 28' tall, sitting on the rock foundation of the home.
Currently the oil fired boiler is connected via 6" pipe. The top of the opening to the chimney is 9" to the ceiling of the basement.The oil fired boiler is going to the scrapyard.
According to http://www.fieldcontrols.com/draftcontrol.php#dctop
I should use a 7" damper because the chimney is over 16' tall and the breech of the boiler is 6".
I'd like to use 6" double wall stove pipe and mount the 7" damper to that. I think double wall pipe should be used because the chimney opening is less than 18" to the ceiling. I don't want to chop a larger hole into the rock wall, though it may fit larger pipe. The opening to the chimney has some sort of soft material around the pipe.
Is it OK/normal to use a 7" damper on 6" pipe?