ductless units – appropriate minimum cooling output in heating climate (zone 5)
Hi, I’m designing a ductless system whose main purpose is to be the primary heating source in climate zone 5. I of course also plan to use it for cooling, but our heating season is 8-9 months long while we only really need our AC (currently, just window units) for 3 months. My decision-making has been primarily driven by what heating loads are required in which parts of the house (I did my own Manual J on Cool Calc). In some areas of the house, if I select a slightly larger ductless wall unit (ie: the 15K hyper heat Mitsubishi wall unit, or the 18K Mr Cool DIY wall unit), this will allow me to use one wall unit instead of two in that area and therefore save money on equipment costs. However, one potential problem is summer cooling: both these units only modulate down to around 6,000 btuh min output in cooling mode. So my concern here is that if I set and forget these units in the summer to whatever cooling temp (say 70F), they would basically be as energy efficient as a 6,000 btu window unit that’s been left on 24/7; in other words, leaving a 15K Mitsubishi hyper heat wall unit with a min cooling output of 6,000 btuh turned on 24/7 in the summer would be more or less comparable to leaving a 6,000 btu window unit AC on 24/7 in the summer. Right? Or am I misunderstanding something here? Thanks.
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