So should I ask them to change anything before it leave the factory? The unit is still being tested overnight at full load. Or there's something I should call the electrician and change at the house?
They already checked polarity , ground , EMI and many interesting things I can't quite understand
Are they building/wiring the unit totally? Plug and play? Is it coming with a power cord and plug installed on the end of the power cord? If so the plug will be rated for 250V 30 amps.
Ask them if they wired the secondary side of the transformer as a Grounded Power System or an Isolated Power System? A Grounded Power System is what you have in your home now. An Isolated Power System is used in Hospital OR, ER, rooms or CATH Lab rooms. In the case of an Isolated Power System the secondary of the transformer is left floating above ground and in your case both output power leads would not have any reference to ground. No reference to the cabinet of the transformer or to any safety equipment grounding conductor.
My guess is if the manufacture is building the unit to be installed in a residential dwelling it will be wired as a "Grounded Power System".
Here in the US NEC code requires a separate grounding wire be installed from the neutral conductor of the secondary winding of the transformer and metal cabinet enclosure to the main grounding system of the main electrical service. Here in the states, a transformer the size you are using, the feed safety equipment grounding conductor can not be used for the ground wire. a separate ground wire must be installed. All grounding within the premise has to be on the same ground plane.
I have no idea how it is done in the country you live. You might ask the manufacture that is building the unit for you. He surely knows.