Off Grid A.C.

TC McClure

New Member
Joined
Jun 27, 2021
Messages
18
I'm not sure if the summers are hotter or I'm just getting older but I find my self thinking seriously about installing A.C. in our off-grid log home. The current swamp cooler we use keeps the house 15 degrees below the outside temperature but when the temps get above 95 degrees, it's no longer pleasant. Would love to hear how you off-gridders are coping with the summer heat. We live in an inland valley of southern California where the summer temps range from 95 to 105 consistently. We only have 120 VAC with no easy way to expand to 240 VAC.
 

Wibla

Engineer
Joined
Jun 6, 2021
Messages
262
Air conditioning requires energy. Do you have the extra energy to spend on it? or can you add on enough solar to offset the extra power usage?

Modern mini splits are pretty frugal, and generally have inverter driven compressor these days (no massive surge), but they still need power to run, and the kWh's stack up really quickly.
 

TC McClure

New Member
Joined
Jun 27, 2021
Messages
18
Thanks Wibla, I always appreciate info from an engineer. I do have plenty of energy, my Outback 80 is usually floating by 10 AM. I also could add panels. The challenge would be adding batteries. My battery house is almost maxed out (poor planning in 1985). I currently run 20 Trojan 105s. Perhaps there are batteries that would have more kWh's in the same footprint.

I have been looking at mini splits and they are available in 120 VAC. Do you have any experience with 120 VAC mini splits?
 

Wibla

Engineer
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Jun 6, 2021
Messages
262
Let me guess, that's a 4s5p bank, giving you a 24V/1125Ah system? About 27 kWh (13.5 kWh usable)? If you hit float at 10AM, you planned your system right. How big is your solar array? and how big is the 120V inverter? Do you have a shunt power meter, and know how deep you discharge the batteries overnight? The last bit is critical to know how much leeway you have for extra energy usage.

I don't have any specific experience with 120VAC mini splits, but the usual recommendations apply - don't get the cheapest, don't get the most expensive, look at both power and SEER ratings. I'd be very mindful of when the batteries hit float after adding a significant load like an AC, and would probably avoid running it when the sun isn't providing power to your system.

As for power density and batteries - lithium is the future there. Each string of 8S (24V) 280 Ah lifepo4 cells give you about 6.5-7kWh of usable energy, so to gain any real capacity you would need to get 24x 280Ah cells and hook them up 8S3P, or preferably as 3 separate 8S batteries with their own BMS's connected to the same busbar. This might be worth looking into when your current Trojans give up the ghost, but not before.

You can also go 48V if you want to significantly expand your solar - as doubling the battery voltage also doubles the power output it can support, from 2kW to 4kW in your case. At that point, you're looking at needing 16S lithium, and that means going for a 16S2P battery if you want more battery capacity. That's significantly more money, but also significantly more battery. I don't really think you need to put that on the top of your list, though.
 

Off Grid Thad

Pound to fit, paint to match.
Joined
Nov 18, 2020
Messages
56
Location
Cascade Foothills
I am on my 5th day after installing a pioneer 12000btu/120v mini split in our off grid container home.
I have no idea how we survived without.
Window units drawing 1200 watts that cooled a 1/4 of our space and were so loud we couldn't stand to be near it to enjoy the cool.
Now we can't hear anything using 1100 watts and cooling almost all of 920 square feet of a well insulated metal heat sink.
About 900 installed.
I say don't hesitate, If you have the solar to spare.
The drain tube on it is a constant stream outside, mold being an ongoing issue, this is great.
 

TC McClure

New Member
Joined
Jun 27, 2021
Messages
18
Thank you Wibla and Thad. Exactly the information I was looking for. Thad, did you install the mini split yourself? I saw the unit I assume you bought online and was wondering if that compressor will only service one cooling unit or if more could be added later. Is one wall unit cooling the entire 900 SF? If so, very impressive.
 

Off Grid Thad

Pound to fit, paint to match.
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Messages
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Cascade Foothills
Yes I installed it myself. Quite simple. Lots of good advise at the University of YouTube.
No you cannot add a second indoor unit, that is a multi zone system that is available, at additional cost.
My containers are well insulated with spray in foam. 1 unit is cooling 900 SqFt yes, with the addition of 2 small 12v Ebay special ceiling fans. I have 1500ah of useable lithium (80% of the 272). That keeps it comfortable until 8 or 9 pm and bats are floating at 13.4 by 10 am when it starts to heat up. My panels put out a max of 1150watts at peak in the day. So all numbers being considered, we don't even notice the power draw.
 

Off Grid Thad

Pound to fit, paint to match.
Joined
Nov 18, 2020
Messages
56
Location
Cascade Foothills
The outside pad took 2 days to pour and set.
I used rubber mounts from amazon set into the concrete pad to mount it on.
 

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Off Grid Thad

Pound to fit, paint to match.
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BTW
This might be worth looking into when your current Trojans give up the ghost, but not before.
Don't wait until the last few watts of lead acid are on their death bed. It takes a bit of change over to install lithium, if you do a build yourself you also have to take into account shipping time, upwards of 3 months. I installed my new batteries in my house as apposed to having them in an outdoor shed. That required a near total rebuild of my system, but as much of it was cobbled together over the last 15 years it has been a good time to redo and finish.
LFE is at a low price now, comparably the same as, if not deeper than, lead acid if you do a self build. Once built they can selectively combine with your existing system and replace when necessary.
 

Wibla

Engineer
Joined
Jun 6, 2021
Messages
262
Don't wait until the last few watts of lead acid are on their death bed. It takes a bit of change over to install lithium, if you do a build yourself you also have to take into account shipping time, upwards of 3 months.
Ah yeah, that's a good point. I could have phrased that better.
 

svetz

Works in theory! Practice? That's something else
Joined
Sep 20, 2019
Messages
5,091
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Key Largo
If the swamp cooler is exhausting moisture into the cabin it'll make it less efficient at cooling as the humidity builds up and makes it less comfortable inside. We used a whole-house fan at night to replace the interior moist air with dry outside air overnight to "reset" the environment every day (but it was a semi-arid climate and always got cool at night). If the rooftop isn't shaded or has debris on it, a lot of heat might be coming in and retained that way. Cleaning or putting on a coat of Henry's Tropico might help (but the polar-white might not look good if it's picturesque).
 

Mcgivor

Solar Addict
Joined
Jul 24, 2021
Messages
187
With regards to mini split A/C units, it would appear efficiency comes at a cost.

Case in point, I have two 9000 BTU inverter splits, a Diakin with a linear compressor, R32 refrigerant, SEER 28, installed cost ~$750.

The other a Samsung rotary compressor, R 410A seer 18, installed cost ~$425

The power consumption rating for the Diakin is 510W, the Samsung 840W, these are averages, both are capable of both higher and lower depending on demand. This is where the Diakin clearly outperforms the Samsung, the linear compressor is capable of lowering power to 150W in temperature maintenance mode, the lowest seen for the Samsung is 425W.

The Diakin is used at night, Samsung by day as required, the temperature setpoint I use is 28°C, although it may seem high, though lower than outside, the most important factor is, it reduces humidity, which takes the edge off allowing a more comfortable sleep. Being offgrid one still needs to consider the limitations of the battery, hense the conservative use.

Note. The prices stated are in Thailand but demonstrate, to me at least, that it's better to spend a little more up front because batteries will ultimately cost more than the differential between the initial cost of the units themselves. Don't go broke saving money is my motto.
 

ken morgan

Solar Addict
Joined
May 11, 2021
Messages
393
With regards to mini split A/C units, it would appear efficiency comes at a cost.

Case in point, I have two 9000 BTU inverter splits, a Diakin with a linear compressor, R32 refrigerant, SEER 28, installed cost ~$750.

The other a Samsung rotary compressor, R 410A seer 18, installed cost ~$425

The power consumption rating for the Diakin is 510W, the Samsung 840W, these are averages, both are capable of both higher and lower depending on demand. This is where the Diakin clearly outperforms the Samsung, the linear compressor is capable of lowering power to 150W in temperature maintenance mode, the lowest seen for the Samsung is 425W.

The Diakin is used at night, Samsung by day as required, the temperature setpoint I use is 28°C, although it may seem high, though lower than outside, the most important factor is, it reduces humidity, which takes the edge off allowing a more comfortable sleep. Being offgrid one still needs to consider the limitations of the battery, hense the conservative use.

Note. The prices stated are in Thailand but demonstrate, to me at least, that it's better to spend a little more up front because batteries will ultimately cost more than the differential between the initial cost of the units themselves. Don't go broke saving money is my motto.
Welcome Aboard Bro! This gentlemen is the guy that helped me put together my lithium pack. he is well versed and quite knowledgeable while not being conceited like a few folks here can be. BTW getting ready to order another 16 or 32 still undecided, Wife and daughters likes the AC too much at the cabin.
 

TC McClure

New Member
Joined
Jun 27, 2021
Messages
18
Wow! Great information from your experiences with mini-splits and batteries. Thanks a million. Based on your experiences, I'm going to install two stand alone units. A 12000 BTU in the 700 SF great room and a 9000 BTU in the master BR. Our area always cools down into the 60's in the evening when we open up the house and let the evening air in.

Thad, thanks for the picture of your install. I'm intrigued by the concept of a container house. Do you have a YouTube video showing the project?
I'm going to stick with my lead acid batteries. While reading your and Wibla's lithium experience/recommendation, I recall that lithium are heat sensitive (true??) and my battery house is not insulated or sheltered. I don't mind running the generator as necessary at the end of the day.

I wish you guys were around in 1985 when I went off-grid, but you were all probably still in elementary school. Thanks again.
 

Off Grid Thad

Pound to fit, paint to match.
Joined
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Location
Cascade Foothills
In 1985 I was building B1B’s at Rockwell in the Mojave desert.
Thad = Tree Huggin A**Hole Democrat. Once a crappy nickname gets used it sticks, never the good ones. So I embraced it.
I’m Don
Sorry, no online documentation on construction. Too many jurisdictions disapprove of my lifestyle. I can understand their position. Why would they allow a fireproof, storm proof, low “E”, self built, recycled dwelling. So laws and statutes were put in place forbidding it.
One winter a tree fell on my house. Just meant I didn’t have to carry the firewood very far.
There are just too many people around who’s only joy in life is interfering in the lives of others. They insist on being offended or insulted by virtually everything. As if demonizing others might mask their own inadequate lives.
Sorry, short off topic rant.
Short version.
I chose to not flaunt my evil deeds by posting them.
 

Off Grid Thad

Pound to fit, paint to match.
Joined
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Messages
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Location
Cascade Foothills
There is an individual, in a position of authority, who regularly invokes the name of God as her commander. She has decided that "People with Wells, Septic systems or Solar Panels, should be paying Water, Sewer sand Power bills like everybody else" Also adding that each location should pay for the installation of meters to gather that billing information.
Thankfully she is recognized as Bat Sh*t crazy and most just ignore her.
BUT
There will come a time when her support is required for something and,,, Well,,,, Quid Pro Quo.

Once enough bureaucrats see $$$. We have all seen dumber things from our elected officials.

On a lighter note.. It is 83 outside and 65 inside.
 

ken morgan

Solar Addict
Joined
May 11, 2021
Messages
393
There is an individual, in a position of authority, who regularly invokes the name of God as her commander. She has decided that "People with Wells, Septic systems or Solar Panels, should be paying Water, Sewer sand Power bills like everybody else" Also adding that each location should pay for the installation of meters to gather that billing information.
Thankfully she is recognized as Bat Sh*t crazy and most just ignore her.
BUT
There will come a time when her support is required for something and,,, Well,,,, Quid Pro Quo.

Once enough bureaucrats see $$$. We have all seen dumber things from our elected officials.

On a lighter note.. It is 83 outside and 65 inside.

You cannot start a story like that without giving details. if for no other reason that eventually this bat shit crazy female might make it higher in the ecosystem of politics and might be elligible for a national level position.... not letting the rest of us know could end up with us inadvertently voting for this "3rd generation double inbred".

If you have no USMC experience here is the generic explanation of a 3rd Generation inbred.

"3rd GDI" is short hand USMC slang for when you take two separate familes...one from the country side, and one from a major metropolitan city you then inbreed the families country only, city only, and then inbreed the offspring from the two families for another 3 generations. and come out with the worst possible mix of f****d up DNA. generally identifiable by their appearance and comments. They walk around and drool and stumble like something from the walking dead while spouting various socialist/communist talking points.
 

TC McClure

New Member
Joined
Jun 27, 2021
Messages
18
Back to Solar talk:

Thad, I'm leaning toward following your lead and buying Pioneer, a name that comes up often and has your positive feedback. In one of your earlier notes you said that it was using 1100 watts. How did you get that exact measurement? Was there any variation or was the 1100 constant?
 
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