Replies

1. 
   user-2310254 | Feb 26, 2022 09:24am | #1

   Sam,

   Ideally, you would use an accurate Manual J to determine the load. If it's an open floor plan, a single mini split is probably sufficient. If it's chopped up or you expect occupants to keep the doors closed, a ducted mini split would probably deliver better comfort.

   To learn more about who should calculate your Manual J, see https://www.greenbuildingadvisor.com/article/who-can-perform-my-load-calculations.

2. 
   paul_wiedefeld | Feb 26, 2022 09:55am | #2

   Manual J then ducted.

3. 
   SamSam1 | Feb 26, 2022 11:42am | #3

   Thank you for your reply. Please help me with this -- My T24 guy says that for I don't need to do Manual J for such a small project (ADU 1200 sqft) as mine. I have attached the plans again, please provide an honest feedback.

   
1. 
   paul_wiedefeld | Feb 26, 2022 12:31pm | #5

   It’s a small investment of time and/or money on an expensive piece of equipment that controls comfort on a brand new building. The size of the building isn’t really relevant here. There are only so many sizes of equipment at your probable load, so it could be guess-estimated, but a half hour seems easy enough. By going with ducted instead of multi-split, you’ve probably saved the cost of dozens of manual Js.

4. 
   leon_g | Feb 26, 2022 12:31pm | #4

   For what it's worth, I hired an HVAC consultant to help design our HVAC system, a portion of which had a separate 600 sq ft ADU. For that area, he recommended a single zone ducted mini split (PEAD). The ducting is to ensure that air gets to all the areas of the ADU (bedroom, living, and bath).

   I think the general preference is for a ducted unit serving multiple areas rather than separate heads in every room, since in most cases the latter will lead to oversizing, not to mention the added cost of all the equipment.

   But as others said, you need to have some load calculations to properly size the equipment, even if it may not be required by T24.