Offgrid Shop

[derbuechsenmacher]

I'm building a new shop and want to make it off grid. I have a 120V inverter already, but want to be able to run some small 240V loads (<30amps at a time). I'm wondering if i can feed the 120 into an auto transformer and take the 240 out and run that into the breaker panel the same way a grid feed would be into the main breaker on my panel. My inverter is a renogy 5KW, and will be using (initially) 3 48V batteries (I've not settled on the solar panels, but I think that is moot in this). Can I do this, or do i need to scrap my 120V inverter and just get a 240V and use a autotransformer to create my neutral?

 

[sunshine_eggo]

proposed option #1: 120V + autotransformer for 120/240V split phase
proposed option #2: 240v + autotransformer for 120/240V split phase
unproposed option #3: 120/240VAC inverter

I would lean towards #3.

 

[MichaelK]

Ummm, 30A at 240V are NOT small loads. We are talking 7200W here. Are you sure about those numbers, or are you looking at the 240V breakers in your electrical panel?

I would completely forget about getting an autotransformer, and instead get a split-phase 120/240V inverter designed to put out that power level. Take a look at Outback's Radian, Schneiders XW, and the Solar Ark.

 

[Hedges]

So if that's a 30A 2 pole breaker, properly powering a load <= 25A at 240V, could be up to 6000W. Still a bit much for a 5kW inverter. If less, might work.
Depending on the characteristics of the load. Resistance heater? Incandescent lamp? LED lamps? Motor?
You need to understand the running watts, power factor or VA, and startup amps.
If the load is a big induction motor you're going to need something hefty to get it going. If brush type, not so bad.

Can you run a wire to the shop, even 12 awg? That could save you a lot of money vs. an entirely offgrid setup.

 

[400bird]

Also, "a shop" to me implies things like tables saws, air compressors, and other large(ish) motors. You're going to need an inverter with a pretty good surge rating to start those.

Can you define some for your loads?
What inverter do you have?

 

[12VoltInstalls]

Can you define some for your loads?
What inverter do you have?

He has a renogy inverter.
Probs not what I might do.