I have a doubt regarding the earthing of an appliance and its separate isolation transformer. Consider the following simplified schematics; this is my first guess at which earth each chassis should be connected to: connect the appliance chassis to the local earth, not the supply earth. Is it correct? What is and why? I'm sure it has mostly to do with the tripping of the residual current device when a fault current occurs to enclosures, but I haven't been able to get to the bottom of it.

This is also a general question, as I need to make sure the isolation transformer can be removed (appliance directly connected to the supply) without rewiring anything: there are therefore 2 cases of which one (n°2) is totally generic.

![schematic](https://i.stack.imgur.com/Ndd9R.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fNdd9R.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)

![schematic](https://i.stack.imgur.com/oqXJq.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2foqXJq.png)

Context: France and Belgium.