So I am re-doing the ductwork in my girlfriends house and just need a little help sizing the main and supply branches. The house is an 1100 sq ft pre-fab rancher and has that mobile home type ductwork where there is square duct running through every floor joist and it’s all interconnected.
Well whoever had the house before her decided that that wasn’t good enough for them and cut into the existing ducts and ran flex duct off of it, and did just a terrible job, so basically both systems are trash now.
What I want to do is use round metal pipe supple pipe that runs down the middle of the house and use reducing wyes to run to the individual registers. The AC is a 2 ton Weatherking and the heat is a 76k BTU propane furnace, and they use the same ductwork.
My question is can I use 10" round duct as the main running down the middle of the crawl and use 6" pipe as the branch lines? I want to take advantage of the weather and get this all done before the heat is needed. Any help would be greatly appreciated. Thanks.