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Multiple Inverter Usage
#1
So I am working on my own PV Powerwall to run my small workshop and I have one question in particular that I have not been able to find a clear, concise answer to.

Everything I've come across so far either discusses trying to use multiple inverters to drive a single load(Not what I need), or makes a statement similar to "use a smaller inverter for light loads and a bigger one to run heavier loads." with no discussion on how this is setup and things to do or not do.

So, can you use a single battery bank to run multiple inverters to drive separate loads?

Assume US 120V 60Hz AC outputs.

Example 1: A PV array runs through a MPPT charge controller that charges a battery bank. An inverter(A) is connected to the + and - of the battery bank and the AC out is wired into the lights. A second inverter(B) is connected the +/- of the battery bank and is wired to the outlets in the shop. The outlets and lights all share a common ground wire. Neutrals return to respective inverters.

Example 2: A PV array runs through a MPPT charge controller that charges a battery bank. An inverter(A) is connected to the + and - of the battery bank and the AC out is wired into one leg of a breaker panel. Small loads are connected through standard AC breakers. A second inverter(B) is connected the +/- of the battery bank and is wired to the other leg in the panel and carries heavy loads. The AC panel has common/bonded neutrals from both inverters, but the hot sides are separate. 

Is this essentially how this is done? 
If not, how is it wired so you don't anger the pixies and release the magic smoke?
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#2
Inverter to use light load and one to use heavy loads means you have two power panels. 1 inverter is connected to one panel, the other inverter is connected to the other panel

They can run off the same battery bank without issues as long as the combined max consumption of the inverters does not overload your wiring and/or cells max amp discharge.

You *can* have 1 inverter run one leg of the 240 panel, and the other leg run the other leg. In the panel you can have 2 neutral bars and 1 common ground bar. You would keep the neutrals separate to the respective inverter.
However, you "can not" use a 240V load in such a panel. Also, I do not believe this would pass code inspection. In fact, I'm pretty sure that it would fail just because of the "possibilities" of a goof up on wiring. Plus a slew of other issues.

It would be best to have 2 sub-panels 1 for each inverter. This is for safety and easy of diagnosing any issues.
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#3
You don't usually want to have two inverters depending on the load. Most decent inverters allow you to 'daisy-chain' to increase the output. But that doesn't mean you can turn one off and turn it on when you need the extra power (although it may be possible). Most of the time it's to increase available power. So if you need 6kw of power, but only have a 4kw inverter, then by daisy chaining it with another 4kw inverter you will get a total of 8kw. For example multiple PIP4048 can be daisy chained up to 6 units. Same with Schneider and Victron stuff. In order to do that, the inverters have to sync up through some communications cable, so they their waveform output will match. THat means you just can't get two cheap inverters and hook it up in parallel to 'add' the available power.

But you can share multiple inverters to a battery bank. That's not an issue. Just connect each inverter to the same battery bank. So the above daisy chained inverters can be connected to the same battery bank

Solar --> Charge Controller --> Battery --> Multiple Inverters
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#4
(02-04-2019, 10:56 PM)Korishan Wrote: However, you "can not" use a 240V load in such a panel. Also, I do not believe this would pass code inspection. In fact, I'm pretty sure that it would fail just because of the "possibilities" of a goof up on wiring. Plus a slew of other issues.

Agreed.

And thank you for the clarification. I was leaning towards neutrals needing to return to respective inverters, and they should not be bonded/made common, but I had not found anything clearly explaining it.

Thank you again.
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#5
The reason the Neutrals need to stay separate is because that's the return path for the power. If they are bonded, it's possible the current could flow the wrong path and go through the wrong equipment. And we know what happens when power flows where it shouldn't.
Church1182 likes this post
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