Split Phase vs Parallel & AC Breaker Panel for dual Victron Quattro 10k

[hipshotgunslinger]

Hello! With lots of help I think I have the DC side of my system nailed down. Now I'm stressing over the AC side and could use some advice. I've searched here and on YouTube to no avail.

I have dual Victron Quattro 10k units, dual Victron 450/100 mppts, 1120ah of 48v batteries, 15.3kw of panels (only half will be hooked up for maybe this year). Currently on grid and moving off grid. My plan is to put in a new breaker panel and in the short-term put about 1/2 of the house running on the solar. Once everything is moved over I am right on the border of a 10k unit being enough, but since I live at 9400' in CO and units are derated I decided to double up for redundancy. I have some questions:

1. I understand that I "double my power" if I hook the units in parallel, but it would still be 120v. Wouldn't the same "technically" apply if I hook them up in split phase since each unit is running half of the panel? I can't find anything on how to wire the panel differently for each scenario. Split phase makes sense since that is how panels are normally wired. Is it as simple as the panel gets wired the same and the change occurs in the Quattro unit settings or is the panel wiring different? We currently don't use any 240v electronics, but we do have a backup compressor and dryer that are both 240v so I'd like to easily be able to convert to 240 down the road w/o too much effort.
2. Victron specs 1/0 wire from the inverters (136 amp). 136 x 1.25 = 170 amp breaker right? So I will go with a 200 amp panel. Can the main disconnect just be 200 amp or do I need the less common, more expensive 175 main? BTW the continuous load per inverter is 8000w. So if I divide that by 120 that is 67 amps continuous per inverter. Does any of this change if I choose parallel vs split phase?

 

[sunshine_eggo]

1. in split phase you will have two legs of 120V each capable of 10,000W for a total of 20,000W. Between those legs you will have 240V.

Each inverter has L, N and G output.

to your panel, Inverter #1 would have L, N and G mapped to L1, N and G.

to your panel, Inverter #2 would have L, N and G mapped to L2, N and G.

2. If the wiring can handle 200A/1.25 = 160A, then I don't see a problem, but I'm not a NEC code monkey.

While the max continuous is 8000W, you can run 10,000W for 30 minutes, so you need to size for 10kW.

 

[hipshotgunslinger]

1. in split phase you will have two legs of 120V each capable of 10,000W for a total of 20,000W. Between those legs you will have 240V.

Each inverter has L, N and G output.

to your panel, Inverter #1 would have L, N and G mapped to L1, N and G.

to your panel, Inverter #2 would have L, N and G mapped to L2, N and G.

2. If the wiring can handle 200A/1.25 = 160A, then I don't see a problem, but I'm not a NEC code monkey.

While the max continuous is 8000W, you can run 10,000W for 30 minutes, so you need to size for 10kW.

So if I'm still doubling my output in split phase and getting the 240v then is there any reason at all to wire them parallel? Is there any benefit?

 

[ricardocello]

So if I'm still doubling my output in split phase and getting the 240v then is there any reason at all to wire them parallel? Is there any benefit?

most US houses are wired for split-phase, and practically all residential panels are split-phase.
Your 120V loads won’t know the difference if you have a split-phase panel.
And if you ever have 240v appliances later, you want them to work.

There is no advantage I can think of to wire them in parallel.
There are lots of disadvantages: Cable lengths must match, your main breaker must double in size, etc.

 

[sunshine_eggo]

They are technically in parallel either way. They're either parallel single phase or parallel split phase or even parallel 3 phase if you get a 3rd inverter.

For a residential application, there really is no good reason to parallel in single phase.

 

[hipshotgunslinger]

They are technically in parallel either way. They're either parallel single phase or parallel split phase or even parallel 3 phase if you get a 3rd inverter.

For a residential application, there really is no good reason to parallel in single phase.

Thank you, that is what I was thinking, but couldn't find any documentation on how to wire it other than people doing split-phase. I guess that is why. SP seems like a no brainer, especially since I won't have to touch it to utilize the 240 down the road. I just wanted to make sure I still got the advantage of 2 inverters no matter how I did it.

 

[sunshine_eggo]

Thank you, that is what I was thinking, but couldn't find any documentation on how to wire it other than people doing split-phase. I guess that is why. SP seems like a no brainer, especially since I won't have to touch it to utilize the 240 down the road. I just wanted to make sure I still got the advantage of 2 inverters no matter how I did it.

Yes. You will get 20,000W however you wire it.

 

[hipshotgunslinger]

If I have 2 separate breaker panels, one from the Victron's and one from the grid (for now until we get the solar fully functional) how do they get grounded. Does the inverter panel just connect to the main panels ground and if so does it get bonded or is it treated like a sub-panel and not bonded?

 

[ricardocello]

If I have 2 separate breaker panels, one from the Victron's and one from the grid (for now until we get the solar fully functional) how do they get grounded. Does the inverter panel just connect to the main panels ground and if so does it get bonded or is it treated like a sub-panel and not bonded?

My opinion: One ground system for the entire house, so connect the grounds from the grid panel and the Victron panel.
But I’m not an electrician. This gets into the definition of a “separately derived system” in the NEC.

I would also expect a neutral-ground bond in BOTH panels.
The L1 and L2 circuits should never mix between the two.
@timselectric