Sizing minisplits
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I have gone through and figured my basic heat loss calculations for a home I am trying to convert over to be heated by mini splits. I figured my calculations with an outdoor design temperature of -7 F.
I will be installing Fujitsus which state that they retain their rated heating capacity down to 20 F.
My outdoor design temp is much lower at -7 F.
I do not want to oversize the units but how do you reconcile the difference between the two temperatures and pick the right size unit?
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Given you cold temps you should consider one of the units that compress part of the gas twice this allows them to operate at colder temp without much reduction in output.
I think most manufactures have models with this technology marketed under different trade names.
Mitsubishi call it” Hyper Heat”
https://www.mitsubishicomfort.com/benefits/hyper-heating
Fujitsus calls it xltH
https://www.fujitsugeneral.com/us/residential/technology/xlth-low-temp-heating.html
Walta
Thanks Walta I was planning on using the cold temp units from Fujitsu. I have one in my house now and have been real happy with the performance, but I am still not sure how to size the units as the max. heating capacity starts to fall off below 20F.
You can search through here:
https://ashp.neep.org/
They provide specs down to 5F for the units, any of the ones have good maintenance capacity between 47F and 5F will typically deliver 90% of rated down to 0F. Most cold climate units are rated down to -15F but will deliver heat at reduced cacpity even bellow that.
Once you find a unit you like, you'll have to do a bit of digging for the engineering manual for it on the company's site. This will have tables for capacity vs temperature (ie: https://nonul.mylinkdrive.com/files/M-Series_Engineering_Manual.pdf )
Thanks Akos, so I checked ASHP and found a Fujitsu AOU30RLXFWH with a rated capacity of 32,000 BTU/h at -15F delivers max but of 22860. My design temp is -7F so I am figuring at this temp my heating capacity would be around 26,000 BTU/hr.