Modifying a metal flue

[chrisfallis]

Ten years ago I installed a wood boiler in my basement. The stovepipe went from the boiler to the new metal chimney that I installed in the old masonry flue. The question that I have is about the "T" fitting between the stovepipe and the chimney. In my last installation, the bottom part of the "T" was closed off. Smoke came in from the stovepipe, turned 90 degrees and went up the chimney. Now to my present house. I have two gas furnaces, the newest of which probably dates to the Roosevelt administration. These are connected to masonry chimneys with metal stovepipes and "T" fittings but in both cases, the bottom of the "T" fitting is open. There is a fairly significant draft that I can feel going into the fitting. Combustion gases are obviously making that 90 degree turn and going up the chimney, but I think a bunch of my room air is also leaving that way. All the time, not just when the furnaces are on.

Do these openings add any value? Can I cover them up and reduce the lost heated air going up the chimney?

Regards,
Chris Fallis
Colorado Springs

 

[begreen]

Which Roosevelt? :lol:

It sounds like there may have been a barometric damper in there at one time, but hard to tell without seeing it. If you cover them up, the draft could be too strong on the furnace. Best to have it checked out with a draft gauge. They may need to put the barometric damper back in.