Hybrid Inverter sizing advice

beckkl

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I'm going to be adding two bedrooms and a bathroom to a pole shed I have on a remote property, and am looking to install a 3 zone mini split (27000BTU/22 Seer). I am considering getting the 3K growatt unit (120V). By my calculation mini split could draw 1227W (27000/22). The only other loads are somewhat trivial (Starlink, router, a few POE cameras, and lights). 3K seems like plenty, but I am not sure if I am missing anything? Is there any point in looking at 240V/split phase with this type of usage?
 

beckkl

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Link to 120v 27kbtu unit? Largest i have seen is 9k, the rest are 240v
Well, I provided I used a double pole breaker in the panel, I would still be way under the 3KW, no?
 

feo

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Well, I provided I used a double pole breaker in the panel, I would still be way under the 3KW, no?
That wont turn on the mini split. With luck nothing happens, without shock/fire hazard.

You would need either:

1) 240v only (EU spec) inverter - no usa outlets or other equipment

2) an autotransformer on top of the 120v or 240v inverter (signature solar, victron etc). $$$ and wiring fun

3) inverter with split phase support ( 120/240v)

4) several 120v mini splits

Choose your poison kind of scenario, I am sure somebody will post more options.
 

beckkl

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That wont turn on the mini split. With luck nothing happens, without shock/fire hazard.

You would need either:

1) 240v only (EU spec) inverter - no usa outlets or other equipment

2) an autotransformer on top of the 120v or 240v inverter (signature solar, victron etc). $$$ and wiring fun

3) inverter with split phase support ( 120/240v)

4) several 120v mini splits

Choose your poison kind of scenario, I am sure somebody will post more options.
Looks like growatt does make a split phase inverter.
 

Rednecktek

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Your split phase inverters start at 5kw and you can't use the European 220v versions for doing it without some serious transformer black magic. The phases for running North American 220v stuff have to be opposite wave form to run and the European models are just a single 220v leg and single wave form.

Even the 5kw and 6kw and up inverters are really just a pair of regular AIO units strapped together and with a control board to make sure AIO1 is out of sync at the right rate from AIO2.

When you look at the 3Kw systems and they say they're parallelable, the 6Kw are just 2 of those in the same box.

OK, I think I've beaten that horse to death. Check the spec sheet of the AirCon unit you're looking at for maximum amperage, wattage, wattage of each indoor unit, etc and add them together so you know the 2 most important things. 1: Total wattage to run all the bits at max load, and 2: Maximum startup amperage (to calculate surge wattage). Once you have those as your base line, you can start adding up the additional wattage you'll want for the lights and internet and coffee pot and tv and such.

Add all that up together and round up to the next available size. Worst case scenario you're doing multiple inverters and paralleling them together above and beyond the 220v split phase, i.e. 2 of the 5Kw's paralleled for 10Kw at 220v split phase.

Air conditioning, next to heat, is murder on off-grid systems.
 

beckkl

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Your split phase inverters start at 5kw and you can't use the European 220v versions for doing it without some serious transformer black magic. The phases for running North American 220v stuff have to be opposite wave form to run and the European models are just a single 220v leg and single wave form.

Even the 5kw and 6kw and up inverters are really just a pair of regular AIO units strapped together and with a control board to make sure AIO1 is out of sync at the right rate from AIO2.

When you look at the 3Kw systems and they say they're parallelable, the 6Kw are just 2 of those in the same box.

OK, I think I've beaten that horse to death. Check the spec sheet of the AirCon unit you're looking at for maximum amperage, wattage, wattage of each indoor unit, etc and add them together so you know the 2 most important things. 1: Total wattage to run all the bits at max load, and 2: Maximum startup amperage (to calculate surge wattage). Once you have those as your base line, you can start adding up the additional wattage you'll want for the lights and internet and coffee pot and tv and such.

Add all that up together and round up to the next available size. Worst case scenario you're doing multiple inverters and paralleling them together above and beyond the 220v split phase, i.e. 2 of the 5Kw's paralleled for 10Kw at 220v split phase.

Air conditioning, next to heat, is murder on off-grid systems.
Thanks. I'm looking at 2 of the 3K units or one of the 6K units. Should be WAY more than I need, even with startup. Like I said, this is a vacation-type property (bedrooms in the back of a pole shed), so if for some reason I had to switch off the air in one of the zones, or heat with a propane unit in a certain situation it wouldn't be the end of the world.

It does seem though, that there is a gap in the growatt product line, which is having a split phase version of their 5K unit. This unit accepts up to 450V of PV, which is huge for me. The 6K unit only accepts 250V.

Maybe the MPP LVX6048 is a decent choice..... although a bit pricey and I don't need the grid functionality.
 

Rednecktek

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Just remember that those are basically dual units so plan the wiring and paneling as such. 2 sets of panels, 2 combiner boxes, etc.
 

Rednecktek

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Nope, right there in the description it says:

HYBRID LV6048 6kW Split Phase 120V/240V- 2 x 80MPPT Inputs (8Kw Solar)​


If you grab the updated manual it shows on page 9 it shows 2 PV inputs.

It's the same money either way, the biggest advantage to doing a 6Kw over 2x 3Kw's is that with the 6Kw there's only 1 AC-In, 1 AC-Out and 1 DC-In, so you save on wiring as opposed to 2, 2, and 2.
 

Rednecktek

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Oops! Yup, I missed the X in there. I sit corrected. :)

450Voc! Wow! That'd be a 10s/3p to top that guy out on my panels. Gotta love that low frequency though.
 

nativerobin

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Apr 28, 2021
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I started with the LV5048 inverter, Ii is basically the same as the LV6048, just 5k instead of 6k watts. My 5k unit worked fine on house until i turned on the electric drier, and it would overload the system and shut down. If you look at the manual you'll notice it only needs a 40 amp breaker in your main panel so its not going to run much at 240volt. My drier is 230v 30 amp plus the rest of the house over loaded every time. You can wire 3 of these units in parallel (add those amps), which I did and they more than power everything I throw at them. One unit did power my 240v 20amp well pump.
 

beckkl

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Yeah, I don't plan on powering a dryer with it. Just a few mini-split units from time to time which don't draw nearly that much.
 

SolarPrep

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I would not go that route. Buy the more efficient units made in 208/240, and power them accordingly. Personally, I would not try this with a 3k unit, I'd go at least 5k, there isn't that much difference in price. Try to buy an inverter that has split phase natively so you don't need an auto-transformer.

Also, having used MANY mini splits in projects, I always recommend that people buy the smallest unit they can get for the load, and buy separates. Not the combined multi head unit. Those are much less efficient. 22 Seer for a mini split is lousy by today's' standards. Separates cost more, and cost more to install, but you get what you pay for. Also, long term they will save you a lot of money. I wouldn't even look at units under 30 SEER.

Knowing nothing about your layout, I might add that in our projects, we have often found that a single unit will cool a much larger area than you might supposed. In your scenario, I might think about 2 single head units, around 33-36 seer, and see how it works.

When I put them in, I do all the mounting, conduit, electrical runs, breakers, etc. Then I call an HVAC technician and have them purge the lines and do the coolant.

Good luck!
 

beckkl

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I would not go that route. Buy the more efficient units made in 208/240, and power them accordingly. Personally, I would not try this with a 3k unit, I'd go at least 5k, there isn't that much difference in price. Try to buy an inverter that has split phase natively so you don't need an auto-transformer.

Also, having used MANY mini splits in projects, I always recommend that people buy the smallest unit they can get for the load, and buy separates. Not the combined multi head unit. Those are much less efficient. 22 Seer for a mini split is lousy by today's' standards. Separates cost more, and cost more to install, but you get what you pay for. Also, long term they will save you a lot of money. I wouldn't even look at units under 30 SEER.

Knowing nothing about your layout, I might add that in our projects, we have often found that a single unit will cool a much larger area than you might supposed. In your scenario, I might think about 2 single head units, around 33-36 seer, and see how it works.

When I put them in, I do all the mounting, conduit, electrical runs, breakers, etc. Then I call an HVAC technician and have them purge the lines and do the coolant.

Good luck!
Thanks for the tip. I was also thinking that one of the 35-38 seer might be a better play. It would be awesome to keep the living spaces cool/warm all year. Saves me from having to winterize. I am looking now at the LVX6048. Split phase, 3KW on each.
 

Rednecktek

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If you're going split phase then yes, go for the 220v units. I haven't found a 120v unit over about 22 SEER rating. 3Kw on each leg gives you a lot of power to play with and makes it easier to load balance your draw since you'll be able to drop that right to a bog standard service panel.
 
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