12 / 24 volt air conditioner

theoldwizard1 wrote:

ktmrfs wrote:

That aside the top AC units approach 20 for a EER, and that still puts you in the 50A range from 12V.

A quick look at the amazon units claim decent efficiency, 750W for 13Kbtu vs the 1400W for a rooftop RV, but still that's around 25A at 24V and it requires 50+A for startup.

Comparing a 12VDC A/C to a 12VDC compressor refrigerator (they are close cousins), all dc refrigerators that I know of actually take the DC voltage run it through an inverter and generate a 3 phase AC output (3 phase motors much more efficient than single phase).

It c

an be done, but is it the best solution from a total energy consumption standpoint ?

As pointed out, most mini-splits have a very high EER. There are a few "window shakers" that have similar EER.

even the best units today are around EER=20 or so, vs. about 10 for the typical 13.45K BTU RV AC unit. So 12V or 24V draw is till pretty high. would be nice if rooftop RV AC units were around 15 or so, with decently low LRA so they would easily start and run on a 2Kwatt inverter generator. Best rooftops I've seen are still around 10A vs. 13 or so.

To add to the confusion SEER which is often a higher number than EER

EER is the BTU out/watts in at outside temp of 95F. that's the important one if running off batteries. I've seen units with SEER of 25 but the EER is usually in the 18-19 range.

SEER uses a range of temps from 65F to 95f and units are more efficient at lower outside temps.

If you want to know what it takes to cool the RV when outside temps is high EER is the key and will give you a good idea of the input power needed. Figure a EER of 20 is pretty much best you will get, likely somewhat less.


https://servicechampions.com/blog/difference-between-eer-and-seer/#:~:text=Where%20EER%20is%20calculated%20using,F%20to%20104%C2%B0F.