Converting 120 V, 1 Ph, 2 Wire source to 120/240 V Split Phase for Solar + ESS Inverter Compatibility

[Efreund]

All,

Not sure if anyone has dealt with this before - I'm working on a project for a commercial client that requires battery and solar backup for a single phase, 120 V, 2-wire load. The 120 V, 2-wires come from one phase of a 120/208 V building subpanel.

To provide backup for the load and disconnect from the building in times of outage, I need to connect it to a Tesla Powerwall Gateway-type setup, which requires a 120/240 V split phase, 3-wire input. Most other reputable products in the size range I need have been optimized for 120/240 V residential sizes also.

Are there any problems with using an autotransformer to convert the 120 V, 1 ph 2-wire source to 120/240 V, 1 ph 3-wire to make the connection compatible with the residential optimized battery + ESS systems? Are there any recommendations of transformer products? Any lessons learned, code concerns, or advice?

If this can't work, are there any residential size systems built for 120/208 V, 277/480V, or 120 V, 2 wire 1 ph?

 

[jaggedben]

...

If this can't work, are there any residential size systems built for 120/208 V, 277/480V, or 120 V, 2 wire 1 ph?

The older Outback and Sunny Island systems are 120V, although you have to supply batteries.
There are also a number of plug and play type products available these days.

How much battery capacity and power do you really need? Are you trying to backfeed the grid or just provide backup?

 

[Efreund]

The battery capacity we need is about 10 kWh and about 3-4kW of solar PV. We will probably backfeed the grid with excess solar, but keep the batteries topped off in the event of an outage for load backup.

 

[caribconsult]

I don't think you can 'convert' regular single phase 120 to splitphase 240, you have to have a 3 wire split phase 240 connect to the transformer outside.