question

For a system with a fixed 240v input I like the single large unit with autotransformer approach. It is just simpler to manage, configure, install, scale out. It should also be cheaper I would imagine.

In my RV I have scenarios where I need to manage both 120v and 240v inputs so it is not as simple, but for a house with a 240v input and that wont change, the single unit seems better. You can throw in a 48/10000 or 48/15000 Quattro and have a very nice setup!

I have used option #1 with the autotransformer to create split-phase here in Canada.

Since that time there have been zero (0!) Issues with the setup. I run 2 x Multiplus 5000va 230v in parallel and have frequently run total loads over 7000w for hours without issue.

As my family is off-grid it also feels good knowing I have some redundancy if one of the inverters decide to fail mid-winter etc.

Ah, I like that, a third option for redundancy ...

* Two smaller 230V Quattro inverters to take in 240V from the grid, 240V from the gen (neutral not connected), spit out 240V to 100A autotransformer to sub-panel for two L1/L2 120V supplies.

For example, two 48/5000 at $2330ea for the power equivalent of one 48/10000 at $3778, but more expensive. Is that redundancy worth the extra $1000 though ...

Rough cost comparison (very rough)

• Option 1 : $4457 One large 48/10000 ($3778) plus 100A Autotransformer ($679) no redundancy
• Option 2 : $4660 Two smaller 48/5000 ($2330ea) no redundancy
• Option 3 : $5339 Two smaller 48/5000 ($2330ea) plus 100A Autotransformer ($679) redundant

I don't think there's any benefit to Option 2 ... more expensive, more wiring etc. So it's really a choice if how much is redundancy worth ? Here it's about $900, probably a bit more though with the extra wiring/breakers/etc. more space. And while redundancy is nice, there IS also more to go wrong.

Ah - something I hadn't considered. In the US we have 240V split-phase - the center/neutral is bonded to ground. So we CAN'T take in 240V from the grid to the Quattro, since that would ground one of the legs. Bad things, right ?

Is anyone here using a Quattro 230V model with an Autotransformer as described about ? That is, taking in 240V via US 120/240 split phase, feeding to Autotransformer and outputting regular 120-0-120 split phase ?

Before committing to a rather large expense of non-returnable items, I would like to have some confirmation .....

im assuming option#3 is 2x 120v quattros run in split phase config? if so the redundancy comes from autotransformers ability to step up 120 to 240? what happens if 1 inverter kick the bucket without autotransformer, will it still run 1 leg/side of subpanel or second one stop functioning if one dies? sorry for highjacking jsut trying to figure out a best scenario for a grid tied cabin with crappy grid (1 big 230v vs 2x120v in split phase)

thanks!