Mitsubishi ASHP – Questions about hitting the +5 & -13 limits
We are in Minnesota (Zone 6a). 2200 sq/ft single level, FPSF slab on grade. We have a pretty good house with R60 in ceiling (2″ CS sprayfoam & blown cellulose), R34 10″ densepack double stud walls, 2″ under slab, 4″ rigid on perimeter slab. .79 ACH. 9.6kW solar PV Built in 2018
Mitsubishi claims 100% heating capacity down to +5. And will provide heat down to -13. But what does that really mean?
So this is the first winter living in our new house and we are about to hit the -13 claimed heating limit. I am curious, what happens when we drop below that temperature. Will it shut off? Should I shut it off before we hit that mark? Will the unit draw increasing amounts of electricity with no heat produced?
Mitsubishi says 100% heating capacity down to +5. This extreme cold got me thinking about the claim…is it actually less efficient between +5 and -13? Or is it just unable to provide as much heat in that range and would it make sense to supplement the ASHP with the electric baseboard heaters in that +5 to -13 range?
Heating System specs…
(1) MSZ-FH15NA 1.25 ton indoor head
(3) MSZ-FH06NA .5 ton heads
(1) MXZ-4c36NAHZ-U1 3 ton outdoor compressor
(1) PAC-MKA50BC 5-port branch box (installed in unconditioned attic space)
We have electric baseboard heat for backup and a 27,500 btu gas fireplace.