Ductless sizing in the boondocks
We’re converting a garage in 3A, and trying to properly size a ductless system. HVAC contractors in the area (there aren’t many) are fairly cavalier about sizing (Manual what?).
We estimated a 9,000 BTU would suffice …they’re certain that 1 ton or 1.5 ton Carrier would be necessary. Best we can do is rule-of-thumb-it at this stage. Help me if you can.
Nightime cooling and humidity control is the biggest concern. We’ll have 450 square feet of conditioned space for offices and a small bath. Insulation is to code, sealing is decent. There’s a large window on the southeast wall with big overhang and trees that prevent any real insolation durng the cooling season. There’s a patio door with high performance low-e glass on the northwest side that gets some sun very late in the day in June. No other openings. The floor is slab on grade.
The roof is metal and fairly reflective, an SRI above 50…this can’t possibly require 1.5 tons! But is .75 tons likely to be adequate? And does it matter if I go with the base 19 SEER or will the 25 SEER offer better performance?
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