Minisplit minimum outdoor temp question

ChrisJ

What does the minimum outdoor temp rating actually mean. I.E. if it's rated down to 5F, what happens below that? Does it shut off totally? Does it operate but at greatly reduced output or efficiency?

The unit I'm questioning is a Daikin RXC18AXVJU

GGross

It depends on the model! I know there are some brands that their "standard" heat pump models (meaning not the ultra low temp units) will actually shut off below that minimum temperature. most of the low temp units never shutdown due to low temperatures in a lab setting, so they do not list a shutdown temp, just a lowest temperature they were able to get ratings from.

If I had to guess on that model I would assume it would shutdown around that min temp, but it's not my brand so maybe a Daikin expert will weigh in. Also keep in mind those low temp settings need the wind baffle

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1872003#Comment_1872003

I didn't realize heat pumps needed wind baffles?

I've heard of them on cool units because of the wind blowing through the condenser, but wouldn't that help warm the evaporator (heatpump)?

GGross

https://forum.heatinghelp.com/discussion/comment/1872007#Comment_1872007

Oh you are right they using that for low ambient cooling!

GGross

Looking at that more closely they don't have ratings for it at 5 right? just ratings down to 17? That's not a lot of juice for a cold day. Have you considered the cold climate ones? they are usually quite a bit more money but they at least tend to give you ratings for low temp operation

pecmsg

my basic Fujitsu units shut down at 10* in heating.
I stop using them at30*

GGross

LG has 2 single zone models with ratings at -30f. you can wait another year and the tech will probably make its way to more configurations, these are both small units, but still higher output at 17f

https://media.us.lg.com/m/26d8d4d82299980f/original/SB_SZ_Art_Cool_Deluxe_R32_KSSAL121A_2025_05_19_121743.pdf

EBEBRATT-Ed

Says +5-+55 deg for heating. I would guess 5 degrees is the lowest temp that is practical for heating

Kaos

Since the output drops to 1/2 by 17F, it doesn't matter if the unit runs bellow 5F as its COP will be near 1 anyways. Some units will throw an air temp sensor out of range error if bellow their min operating range.

If you want to heat, get EVI units as these run well into deep freeze without loosing output. 5F is a non issue for these. In colder climates also watch that the unit comes with a base pan heater. Some of these mostly AC heat pumps don't have it.

The wind baffles are needed when heating in windy areas to protect the coil during defrost. If cold wind is blowing through the coils during defrost, all the heat will be lost and the coil will ice up.

Forever_Student

I'd recommend checking the NEEP ccASHP database (link: ASHP) or the AHRI database (link: AHRI Certification Directory). AHRI tells me the system you show in your screenshot still operates at a COP of 1.8 at 5F. Not bad, not great.

As for what happens outside of its range, as noted above, it depends on the manufacturer's programming. Some units will continue to run, but experience reduced heat output and reduced efficiency. Other units might have manufacturer's programming that shuts the system down when outside of range. Have to ask Daikin about this one.

Depending on where you live, if heating is a priority, I'd recommend going with a NEEP-certified ccASHP. (link: ASHP). A cold-climate hp is going to be biased toward heating instead of cooling, and will perform much better at low temps. Daikin is a great brand for MSHP, one of the best. I'd also look into Mitsubishi.