Newbie wants to run 24,000 BTU AC

[Jommy747]

Hello everybody. I have a very specific goal. Run my 24,000 BTU York split unit from noon to 6 pm. So I studied and came up with the following calculations. Please let me know if I made mistakes or this would work. Ok here we go:

The split unit runs on 230 volts. It consumes 700 to 1.200 from when it starts to when the room is cold and run on eco mode. So let’s say 6 hours = 6,000 watts.

i live on an island with limited supply but I could get a huge truck battery 12 v new 1,800 Ah for $300.
i get get a Growatt 3Kv here. I am thinking 3 panels of 400 watts. In the Caribbean we have A LOT of sun hours. On a cloudy day, if I cannot charge full my battery, it’s ok. It’s cloudy and cooler. No need AC.
please let me know what you think. Thank you for the help.

[bcroe]

Run my 24,000 BTU York split unit from noon to 6 pm.
The split unit runs on 230 volts. It consumes 700 to 1.200 from when it starts to when the room is cold and run on eco mode. So let’s say 6 hours = 6,000 watts.

1200 watts times 5 hours = 6000W Hours. I think your best shot would be to
use a mini split or other unit designed to run directly from solar panels. But
you probably will need more panels than that. Bruce Roe

[Jommy747]

Thank you Bruce but when you live on an island in the Caribbean everything you buy ship and import is very expensive. So I have a 2 years old split unit so I plan to use that. Buying an AC solar powered is not in my budget. When you say i probably need more that that, how many? How do you calculate that? Thank you

[bcroe]

If you have already been using that 24,000 BTU, you must have
AC power. Check out its SEER, you want at least 20s. The
economical plan is a Net Metering arrangement with your Power
Company, let them be your infinite capacity, 100% efficient, zero
cost or maintenance, battery.

If you must use a battery, someone here doing so may advise you.
At the least you will need a big charge controller, a big battery, an
inverter (probably 24VDC powered), and a low voltage shutdown
to protect the battery from damage. Panels almost never deliver their
rated peak, so you might need more to compensate for that, and
for the inefficiency of all the above components. In the end a late
high efficiency, direct solar powered unit might still be cheapest.
good luck, Bruce Roe

[Ampster]

I presume the truck battery is Pb? Those are more fragile in the sense that they need to be fully charged every day. Lithium batteries, while more expensive, will be more tolerant of partial charges and allow you to use more capacity or buy less capacity for the same useful capacity... Pb useful capacity is only 50 percent. The price is good for the truck battery but the weight may increase the shipping cost.

[Jommy747]

Thank you. I don’t understand Pb. The truck battery is here local. No shipping. I know lithium is the way to go but $$$$$$

[Ampster]

.... I don’t understand Pb. The truck battery is here local. No shipping. I know lithium is the way to go but $$$$$$

Pb is short for Lead. I understand shipping costs can change the economics and I don't know anything about the logistics to your island.

[Jommy747]

Ok thank you

[MangoCat]

Just to emphasize an earlier poster: many new mini-split AC units have "inverter technology" which in their world means that they can run the compressor at fractional power, just what you need not the full 24,000 BTU or 0. This makes them MUCH friendlier loads under normal circumstances, drawing a more continuous current and in connection with a solar system: needing less battery or wasting less PV capacity when the compressor is cycled off. I have a similar "inverter tech" 12000 BTU marine A/C on our sailboat and it runs happily off of "shore power" at the marina, through a 15A breaker and a 75' 14 gauge extension cord carrying 110V, typical loads run around 4 or 5 amps while it is cooling (though on a blasting hot day it will crank up to around 12A to keep cool...) In theory it would also run through the 12V->110AC inverter we have on the boat, but I've never tried stressing out our alternator or lead-acid house batteries that way.

[SamirD]

I think your best shot would be to
use a mini split or other unit designed to run directly from solar panels.

I had no idea units designed to work directly from solar existed. You have a link to one? I'll research more from there.

[littleharbor2]

EG4 Hybrid Solar Mini-Split Air Conditioner Heat Pump AC/DC | 12000 BTU | SEER2 22 | Plug-N-Cool Do-It-Yourself Installation (PRE-ORDER) - Signature Solar

Airspool MS12: Solar-powered mini split air conditioner (12,000 BTU/1-

DC Solar Air Conditioner Heat Pump | Solar Air Conditioning | Solar Heating | Manufacturers (hotspotenergy.com)

ACDC12C Solar Air Conditioner Heat Pump - Practical Preppers

Solar Powered Air Conditioners: A Comprehensive Guide (cielowigle.com)

[littleharbor2]

Hopefully my previous post will be approved. It simply listed the solar powered mini split ac units I found on the internet. I have no affiliation to any of them. If not, the OP just needs to google "solar powered mini split"

[SamirD]

Thank you so much for the links!! What a rabbit hole! There's a lot of development in this area.

After looking at the various options out there and seeing how there's mini-splits that are basically shipped to a customer turn-key, I would emplore OP to take a look at those systems as they will do the job and are proven setups.

Otherwise, going the route of a diy solar energy system will help that existing system run off of solar--you'll just need to overbuild it since you're using less conventional (and efficient) parts.

[MangoCat]

...seeing how there's mini-splits that are basically shipped to a customer turn-key, I would emplore OP to take a look at those systems as they will do the job and are proven setups.

Otherwise, going the route of a diy solar energy system will help that existing system run off of solar--you'll just need to overbuild it since you're using less conventional (and efficient) parts.

Yeah, I'm on the fence, myself. My workshop is in the planning phase, so I _could_ go with the turn-key solar A/C, but then that would leave me building a parallel system to charge the tools, etc. I do agree, the existing standard A/C compressor is going to need a lot of overbuild / overcapacity to work, and OP may end up with more spare capacity than he knows what to do with by the time he's got the 24,000 BTU conventional A/C running from solar+battery. Also worth mentioning, batteries are rated in charge/discharge cycles - not really years - so if your A/C setup is charging / discharging your batteries 6 to 8 times a day, that 3000 cycle battery will last closer to 2 years than the manufacturer's advertised 10 years.

[bcroe]

The direct PV panel powered heat pumps are another option. They
are generally a big advance in reducing energy consumption and CO2
emissions, with far quieter operation. This without troublesome batteries.

But they still suffer from the problem of renewable energy production
not lining up with consumption. Your situation may usually have good
sun coincide well with the need for AC. Or, it may not, and what about
operation for heating? Batteries may not be a practical fix for energy use
on this scale overnight, and never between seasons.

The PV option HVAC will certainly reduce energy use any time the sun shines,
but never eliminates consumption when used with grid connected backup. If
the sun shines but no cooling is needed, the energy available from those
panels is lost. There is the issue, that once connected to HVAC, the PV panels
cannot be connected to anything else. This is a matter not discussed, and
under some scrutiny here as a partial solution if my net metering ended. Also
not discussed, is the use of dual arrays favoring early or late parts of the day.
to increase total time of capacity operation.

So the best solution depends on each individual situation. Here the favorable
Net Metering program with 1:1 energy exchange allows maximum efficiency
of my facilities, which might not work for many others. It goes like this:

Mini split heat pumps are selected which cover the temp range here, which
can drop well below 0F, and for highest SEER. There is resistance heat
backup heat available, but never used. Instead more mini units are used
which may drop to the same COP of 1 in really extreme cold, but that
condition is uncommon. They all operate on 240VAC, which requires space
for a lot of double circuit breakers, but saves a lot on wiring.

Benefits of these Mini Splits include highest effiency and very quiet operation.
HVAC is decentralized, so no one failure can cause complete system shutdown.
The old duct air system blower is still cycled regularly to help even out temp
and humidity, and to let the electronic air filter remove dust and pollen. They
lend themselves to far cheaper DIY installation, mounted under a large roof
overhang and several feet above the ground (on a brick wall) to stay clear of
snow.

The PV solar system operates independently, with Net Metering giving full
credit for summer KWh, to be used when most needed in winter. The PV
system may be as large as needed, to generate enough energy for 24/7/365
use as needed. No potential PV output is lost. Energy surges are handled
by the PoCo. Of course all electrical, as well as HVAC needs, are covered,
ongoing energy charges for electrical and HVAC are zero. Maintenance is
very low, mostly checking energy flow and reserve from time to time.

Bruce Roe

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