The End of the World finally happened! AC/DC Mini Split?

[Zwy]

I have to wonder…
How would a dedicated mppt controller respond to this situation…

Panels connected to BOTH the eg4 minisplit, AND the mppt controller…

Wouldn’t the mppt respond to the solar when he minisplit kicked on like clouds passing over?
And ramp back up when the mini shuts down?

I see days like today, very humid, sky is somewhat overcast and hazy. Dewpoint is over 70F so it is sticky.

Production actually is fairly steady unless clouds move in and I see less than 1Kw coming in. It would take switching to make it work.

 

[n2aws]

I have to wonder…
How would a dedicated mppt controller respond to this situation…

Panels connected to BOTH the eg4 minisplit, AND the mppt controller…

Wouldn’t the mppt respond to the solar when he minisplit kicked on like clouds passing over?
And ramp back up when the mini shuts down?

I doubt this would work. It'd always try to use the path of least resistance. When the AC is in an idle state, the power would go to the mppt, cuz it'd likely be the only "completed" circuit. but when the relay/contactor/whatever in the AC closed to complete the circuit.. I suspect the startup draw would still be higher resistance than the mppt controller, so I doubt it'd be used to start the unit. *After* it's running, and reaches it's normal running state.. I'm not sure which device would have the lower resistance. But, it doesn't seem like a recipe for success in my opinion.

 

[Supervstech]

I doubt this would work. It'd always try to use the path of least resistance. When the AC is in an idle state, the power would go to the mppt, cuz it'd likely be the only "completed" circuit. but when the relay/contactor/whatever in the AC closed to complete the circuit.. I suspect the startup draw would still be higher resistance than the mppt controller, so I doubt it'd be used to start the unit. *After* it's running, and reaches it's normal running state.. I'm not sure which device would have the lower resistance. But, it doesn't seem like a recipe for success in my opinion.

I agree, but I have to wonder if it would at least allow some use of the panels when the mini isn't running

 

[Sundog33]

I have to wonder…
How would a dedicated mppt controller respond to this situation…

Panels connected to BOTH the eg4 minisplit, AND the mppt controller…

Wouldn’t the mppt respond to the solar when he minisplit kicked on like clouds passing over?
And ramp back up when the mini shuts down?

Not sure what you mean here?? Panels are only dedicated to the Mini Split. In the case of using the Panels for something else you would build up a double breaker box with a splitter to manually direct the PV Power. I see no post from Will that that unit had failures, but I,m sure there are always a lemon.

 

[Sundog33]

I have a few conflicting opinions on this. I'll mention a few below, so others can make an informed decision for their particular use-cases.


I went solar + batteries because hurricanes. a few months ago I was without grid for 9 days, and in 2004 I was without for 21 days.

I like the idea of the AC/DC minisplits for those just getting into solar. But! in my opinion.. for most people that are already doing solar+battery, it's more efficient to use those panels to charge the batteries, and run the minisplit from AC current. That way, even when the AC isn't running, the panels are still harvesting power.

That said.. There are edge cases where it may make sense even when you already have solar+batteries. Ie, your battery is undersized to run your critical loads + the new AC load. or, if you're grid-tied, and the utility has a limit to the amount of power you can "sell" or a limit to the size of system you can have connected to grid (ie, here.. FPL limits us to systems of 10kw, or we need to carry 1 million dollars of liability insurance.

minisplits ARE super energy efficient, and is likely my next large purchase. I'm debating between getting an AC/DC and just not hooking up the DC, unless we get into an extended outage situation. It may be nice to have a couple of my portable/camping panels able to be deployed in the yard quickly in a case like that.

One final thought.. Even in florida summers.. when without power for 9 days, we got away with running a single ceiling fan in the living room (on high), and turning it off when we weren't in there. air movement alone can make a significant difference to comfort levels. Something for others to consider before going with a minisplt for outage purposes.

Well... even with all this talk, I will eventually get a hair up my ass and make a bigger system. I love those EG4 Rack systems. It may take me a while but I'm the kind of guy who needs a project. But I think this is viable for now.

As far as these people around me farming out their roof, selling their power then buying it back for a higher price with no Battery backup. Thats just insane to me. Unless your trying to just save the planet.

I don't want to be Grid Tied at all. Which has its own problems of checking battery levels and dedicating what to power.

As far as a fan. That would not work for me. In the winter I shut off the vent and close the door. If i'm not breathing smoke I'm not a happy sleeper. LOL

 

[n2aws]

I agree, but I have to wonder if it would at least allow some use of the panels when the mini isn't running

I think what we'd end up seeing is that the mppt would always get power.. and the panels wouldn't start the A/C.
Not sure if after the AC (alternating current) starts the A/C (air conditioner), I wonder if the DC would flow to the minisplit or charge controller

 

[Sundog33]

I think most missed the point of this thread. My Goal isn't to save money. Its for emergency backup.
If I was out of power for 21 days. I'd be living high on the hog with AC, TV, Iphone charging and Lights.
Saving money is one thing - having All the things you need to keep you from going crazy... well that's priceless.

 

[pwit]

Regarding the issue of not being able to use the PV power for anything other than the AC unit (unit not on or not at full capacity): would something like the Electrodacus BMS/solar PV charge controller setup work for this?

 

[tomy2]

Yep, that would work. Use a splitter from the Breakers. Very good.
So if I am only running series it will only multiply the Volts correct. If i have say 6 - 200watt panels in series it would only stay like 8amps?
I never see breakers that low? Am I thinking wrong?

Oh I did find it:

DC Miniature Circuit Breaker, 2 Pole 1000V 10 Amp Isolator for Solar PV System, Thermal Magnetic Trip, DIN Rail Mount, Chtaixi DC Disconnect Switch C10​

these breakers are not UL listed .

 

[SolarPowerAficionado]

Yep, that would work. Use a splitter from the Breakers. Very good.
So if I am only running series it will only multiply the Volts correct. If i have say 6 - 200watt panels in series it would only stay like 8amps?
I never see breakers that low? Am I thinking wrong?

Oh I did find it:

DC Miniature Circuit Breaker, 2 Pole 1000V 10 Amp Isolator for Solar PV System, Thermal Magnetic Trip, DIN Rail Mount, Chtaixi DC Disconnect Switch C10​

Series multiples volts and parallel amps so you are correct.

 

[orangezero]

I think what we'd end up seeing is that the mppt would always get power.. and the panels wouldn't start the A/C.
Not sure if after the AC (alternating current) starts the A/C (air conditioner), I wonder if the DC would flow to the minisplit or charge controller

It has been a while, but I believe the video I watched where they took the EG4 minisplit apart there is *basically* an mppt controller inside the unit. So, the question may be "what happens when you hook up two mppt chargers in parallel to the same panels" and I don't know the answer but it doesn't sound ideal.

 

[orangezero]

One final thought.. Even in florida summers.. when without power for 9 days, we got away with running a single ceiling fan in the living room (on high), and turning it off when we weren't in there. air movement alone can make a significant difference to comfort levels. Something for others to consider before going with a minisplt for outage purposes.

I inherited a super old window AC unit when I bought my house, at least 25 years old. I could mostly get my inverter to run it but if other things were running it could start up and reset everything. It was cool to use it with my solar setup for "free air."

Found a clearance Midea AC window unit to replace it, which may be close to the most efficient window unit they make. It uses 20-30% less energy and never trips my inverter (since it is a *DC inverter* style almost like a minisplit).

My point being, I can make my entire house livable in non-emergency situations with a single, quiet 8000btu window unit. It also comes in 12000btu. Or I could afford to get four of them They are often cheap on facebook.

The EG4 certainly looks cool.

 

[n2aws]

It has been a while, but I believe the video I watched where they took the EG4 minisplit apart there is *basically* an mppt controller inside the unit. So, the question may be "what happens when you hook up two mppt chargers in parallel to the same panels" and I don't know the answer but it doesn't sound ideal.

I wouldn't mind seeing this teardown video. Happen to have a link, or remember who did it?

 

[Delmar]

Someone should really come out with a DC transfer switch.

Why not multiple DC contactors. Or a DPDT relay with DC coil? Example

 

[orangezero]

I wouldn't mind seeing this teardown video. Happen to have a link, or remember who did it?

I think this was it.

 

[ArthurEld]

I thought having solar panels running mini splits sounded odd. You'd never have the right amount of power so you're always either wasting some or don't have enough.
I never used one. That's just what comes to mind.

 

[timselectric]

what happens when you hook up two mppt chargers in parallel to the same panels

They fight over control of the circuit.
Neither produce very well. Because they can't find the maximum power point.

 

[timselectric]

Why not multiple DC contactors. Or a DPDT relay with DC coil? Example

It would have to be rated to quench the arc of a high voltage DC circuit.
The parts to make it are a little expensive.
Two breakers with an interlock is much cheaper.
The one that you linked is only rated for 28vdc.

 

[Sundog33]

I thought having solar panels running mini splits sounded odd. You'd never have the right amount of power so you're always either wasting some or don't have enough.
I never used one. That's just what comes to mind.

Isn’t that the case with any Solar Setup.
Depending on the size your always going to have days you produce more power than you can use or don’t have enough.

With the Government 30% tax rebate for mini splits it’s a cheap setup that can pay for itself in 3 to 4 years. Then who cares. It’s just money in your pocket.

 

[Sundog33]

I inherited a super old window AC unit when I bought my house, at least 25 years old. I could mostly get my inverter to run it but if other things were running it could start up and reset everything. It was cool to use it with my solar setup for "free air."

Found a clearance Midea AC window unit to replace it, which may be close to the most efficient window unit they make. It uses 20-30% less energy and never trips my inverter (since it is a *DC inverter* style almost like a minisplit).

My point being, I can make my entire house livable in non-emergency situations with a single, quiet 8000btu window unit. It also comes in 12000btu. Or I could afford to get four of them They are often cheap on facebook.

The EG4 certainly looks cool.

Exactly, if I can run this $1100 dollar - 12000btu Mini Split off the Sun for free everyday and stop my Central from kicking on so much that's money in the bank.
With the Government 30% tax rebate I can claim the dedicated Panels, wires, breakers, ect... with it. If I spent $3000 I'll get $900 bucks back. That's like getting the Mini Split for free. Free is good.

The EG4 12000btu Mini Split is rated at a whopping 22 SEER. The Midea 8000btu is rated at 15 SEER. Not too bad, but my 15 year old Central Unit is 13 SEER so... definitely the Mini Split technology is better but hey, your still getting free AC.