220V to 110V converter

Jadaharabi said

Get an electrician to look at what you have.

You do not want multiple grounds on your system. Strange things can start happening.
The earth between two grounds can act as a battery.

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To be clear this is not a "system." This is a temporary lashup to get 110 (120) at fairly high current "once in awhile.

All US household electrical systems have more than one ground. You sound like you are in Europe? Whole different deal. Here, the 240V neutral is grounded at the pole and at the main box at the house, AKA "meterhead"