# Flex duct sizing



## paul.mcshane.vz1 (7 mo ago)

I'm going to be installing an additional 2 ton central air and gas furnace system in my attic to go along with my other 2 ton system and creating zoned heating and cooling. I am doing all of the setup work myself and then having a professional come in and finish of with the refrigerant and that type of stuff. The unit will be cooling 2 16ft x 20ft bedrooms, a 10x10 bedroom, a 8x8 bath,,, and a hallway. I will be putting in insulated flex returns and supply . I am wondering what size flex duct I would need to use for both the return and supply runs. Any help would be appreciated


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## channellxbob (Sep 27, 2020)

Too many variables? Are you using flex trunks? Are they leaving the furnace in one direction or two or radially? What's the longest equivalent run from return termination to supply termination?
Lots of calculations. You need to lay it out and figure your available static and go from there.


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