Converting 220V to 110V without neutral conductor

[petersonra]

Of course, any transformer usage will only reduce the final available current.

If you have 12 gauge UG wires you could get 100 Amps at 120 V into and out of the transformer system. That ought to be plenty.

 

[Joethemechanic]

BTW, I think this circuit would allow you to use the existing UG conductors with the existing colors and be code legal going the transformer route.View attachment 2566559

Maybe being that each conductor has 600 volt insulation, if we moved the ground/neutral to the center of the high voltage side on the step up transformer we could go to 1200 volts

 

[Besoeker3]

You can't use an autotransformer to derive a grounded conductor in an already grounded system. At best you could derive a neutral which would have to be treated as ungrounded.

Why not? The connections are not isolated from each other.

 

[Joethemechanic]

Why not? The connections are not isolated from each other.

Like this? Seems rather British

 

[winnie]

Why not? The connections are not isolated from each other.

North America uses a 'split phase' single phase system in residences. This means a 240V single phase source with a grounded center tap..

You can take the two hots and use an autotransformer to derive a neutral. But this derived neutral cannot be grounded since that would effectively mean a system grounded multiple times. The net result is that this derived neutral is sort of a bastard hybrid. You have a circuit conductor that is approximately at ground potential, but it isn't actually grounded and you have to treat it as a hot conductor. Since North American wiring for 120V circuits assumes that one conductor is grounded, a bunch of normal wiring practice doesn't work correctly.

Posts 32 and 33 (taken together) show how to use autotransformers to get split phase to the garage with 2 wires, by bringing a single hot and neutral to the garage (so the grounded circuit conductor is continuous). Post 32 shows getting split phase from two wires (hot and neutral), post 33 shows using a higher voltage hot and neutral to carry more power to the garage.

-Jon

 

[Besoeker3]

View attachment 2566564
Like this? Seems rather British

Not British. Residential is 230V 50V. British industrial is 11kV/400V for large plants and sometimes 132 kV for steel mills.

 

[Jraef]

a detached garage with only a 12g 110V supply line running under a lot of concrete

Is that 12ga in conduit or is it UF buried w/o conduit?

If it’s in conduit, use the 12-2 to pull though some 10-3, then put a 30A sub panel in the garage.

 

[zbang]

If it’s in conduit

Post #8

 

[Jraef]

Post #8

Oops, missed that in all the side traffic about movies and such. Looks as though the OP never responded to that however. I wonder if after you made that comment he went ahead and did that, which is why he went radio silent.

 

[drcampbell]

You're still going to be limited to (20 x 240) 4800 kva total.

Oops! I mean 4800 va.

If you do opt for trenching or boring, install a greatly-oversized conduit. It won't add a whole lot to the total project cost and it will accommodate the two fast chargers that have moved from the realm of science fiction to the reasonably-foreseeable future.