3-wire toroidal transformer wiring

I have a toroidal step up step down transformer it only has three wires and a diagram on the side that doesn't mean a lot to me

this was out of a step-up step-down transformer Pictured below that was working fine 250v in 115v out
the problem was the American plugs where not solid enough so i my infinite wisdom a pulled it apart as i do with most things.
but now i cant figure out how to connect it to 220v and get 115v out.

next time i will leave it alone.

3000 Watt 110v Transformers, 220V - 110V Voltage Transformer, Step Up and Step Down, UK to US US to UK Trans formator 3000W


main problem in a nutshell is it only has 2 red wires and 1 black ???

The input voltage goes between "0" and "220V".
The output is between "0" and "110V".

Its ok cheers i have sorted it, its because its a Autotransformer Ha

you are spot-on cheers i was having a blond moment.

Happens to the best of us. :wave:

If you have it connected across NA 240 and use one end to the 120v CT point measure from here to GND to see how much it is above 'zero' .

Quote:

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Originally Posted by Al_The_Man

If you have it connected across NA 240 and use one end to the 120v CT point measure from here to GND to see how much it is above 'zero' .

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There should be about zero relative to the ground on the "RED 110" wire. 120V above ground on the BLACK wire.

Quote:

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Originally Posted by CitizenOfDreams

There should be about zero relative to the ground on the "RED 110" wire. 120V above ground on the BLACK wire.

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Correct.
The reason I mentioned it is that if feeding any 120v devices or outlets, this should be considered the neutral conductor or terminal.