I have a 2400 sq foot home in Massachusetts that I am looking to add AC to and supplemental heating for an old gas boiler. Our preference is a ducted system and a contractor we're interested in going with is suggesting two Mitsu ducted hyper heat minisplits. One for first floor with two air handlers and one for 2nd with one air handler. He performed a Manual J calc which suggested 56k BTU heating, and 49k BTU cooling. He is saying we will need two 42k outdoor condensers (MXZ-SM42NAMHZ) as the units are only "rated" for 32k BTU heating at 17F.
Is it correct to size a heat pump for the "rated" output or should he be using the "max" output? I'm worried the units will be grossly oversized with his approach. I'm working to do air sealing and rim joist and attic insulation which should also lower the manual J estimates.
Is it correct to size a heat pump for the "rated" output or should he be using the "max" output? I'm worried the units will be grossly oversized with his approach. I'm working to do air sealing and rim joist and attic insulation which should also lower the manual J estimates.
source https://hvac-talk.com/vbb/threads/2244175-Sizing-ducted-minisplit?goto=newpost
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