Gas and Oil Home Heating Furnaces - connecting duct work together

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09-22-00, 10:47 AM
Hi,
I need to establish a connection between a 6" piece of round sheetmetal heating duct into the side of a piece of 12" square flat heating duct. How do I make this a proper connection?


09-22-00, 01:46 PM
First, I'm assuming that your square duct is a product called ductboard. (that's a ridged fiberglass board, cuts easily with a knife)
Go to your local home improvement center ans get what's called a 6" round ductboard tap. This will be a sheetmetal coller that's 6" round and about 4" or 5" long with a flat coller around the circumference (if they don't have one you may try getting one from your local HVAC contractor around the corner). Cut a neat (and round) 6" hole in your square duct and insert the 6" tap. (You can hold the tap up to the square duct and make a mark with a magic marker) Stick your hand inside the tap and bend over all of the metal tabs on the back of the tap inside of your square duct. I'm also assuming here that your using flexduct (?). If your flex is already cut to length, take the plastic inside part (with the wire coil) and slide it over the tap. It may be a little snug but that's what you want. Usually contractors use what called a Panduit strap and a handy tool to tighten and cut the strap. When they run out of straps (or lose their panduit tool) they go to the universal standby -- ducttape. Two or three wraps should do it, just make sure the tape is adhered to both the plastic coil of the flex and the metal collar. Now, take the insulation part (ends tucked neatly in, of course) and slide securely over both the tap and the plastic. Make sure the metal is covered so it won't condense and drip water on your ceiling (or anywhere else). One time around with the ducttape and you should be finished!

Good luck!

09-22-00, 01:51 PM
Oops -- I didn't read your post carefully enough there. You do have 6" round SM duct that you're tying into your square duct. Okay -- I think for the sake of simplicity I would probably make the connection between your round pipe and square duct with a piece of 6" flexduct. (it's easier, cheaper, you won't have to insulate, and you don't have to mess with trying to stand on your head in the attic cutting a piece of sheetmetal.
Just follow the instructions on my last post for both ends and you should be fine.
Good luck!