I'm ready to purchase a Mini Split system for the home I'm working on, but this is the first time I have to design and purchase a system from scratch. The Mini Split is the only option for conditioning the air, so please don't suggest another type of system.
I'm working with a frame, vinyl sided home,960 total sq ft. About 450 for the living/kitchen/ dinette open concept. There are 7'6" ceiling throughout.
A 340sq/ft master-bedroom with en-suite and a 120sq/ft second bedroom. The remaining 50sq/ft is second bath and laundry. The homes has R11 insulation in the walls and R13 in the ceilings with a metal roof. Windows are original 1984 single pane with most of them shaded by a carport and porch. I'm in Fla. and need to be sure the tenants will not complain about not being cool enough. Summer temps are mid 90s from May through October. I will need to drop the temp about 20-25 deg most of the year. Heat is needed only about 30 days a year.
I'm thinking I need a triple split system, but I'm unsure of the total BTUs. ( Calculations are varying between 28000 and 36000 BTU) The size of the indoor units is in question in my mind as well.
I am thinking of a unit in the LR, one in the Master and one in the 2nd BR. Is 18000 too big for the main part of the home? Will 9000 be adequate for the master suite? Please understand the walls and ceiling are closed, so adding insulation or replacing windows is off the table.
I have done calculations and the tools I used put things on the borderline, so I am looking for experienced input based on the things I have in place. I don't want to pay for a system that is larger than needed, but also don't want to put in a system too small that will not cool properly. Thanks in advance.