Sizing a concealed duct minisplit for 1000 sf home

Old 01-29-19, 02:11 PM
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Join Date: Jan 2019
Location: USA
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Sizing a concealed duct minisplit for 1000 sf home

Hey all, I am looking for some help in sizing a concealed duct minisplit system for a small house I am building. It is 1000 sf in southern Missouri. two bed one bath 5 windows and 3 single doors. There will be three ceiling registers connected directly to the plenum. It will be all spray foam insulated to the rafters (i.e. attic is conditioned space), which is the part that has me wondering. The website I'm looking at purchasing from recommend a 24k btu system for 800-1200 sf, 18K for up to 800sf. But I know that I've read one of the benefits of spray foam is allowing you to use a smaller system. The cost difference is negligible but I don't want to oversize the system. Is it a good bet that the well sealed house and small number of windows will allow me to use the 18k system? Thanks for your opinions.
Old 01-29-19, 07:39 PM
Join Date: Oct 2016
Posts: 2,179
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Manual J, S, and D is the only way to properly size equipment and duct.
No such sizing chart exists.
Be careful with internet sourced minis, especially the no name ones. Some don’t work all that great and are basically disposable.

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