Hi xmas79
For voltage channel connection, if you have large resistors (1Mohm ) placed on both phase and neutral wires forming an attenuation network with 1kohm resistors (1000:1 attenuation), this would make sure that you have a "protective" impedance in place on both the wires. In case, the wires are swapped, there will be no damage to the meter as the attenuation network in set up in a differential manner. You can scale the attenuation network resistor values based on how much "protection" you need, say, using 2Mohm and 2kohm resistors instead of 1Mohm and 1kohm resistors. Is this something that might work for you?
Differential attenuation network proposal:
In this way, you need not use AD8479 at all. Once you do this change, please provide your complete schematic so that I can check to see if the grounding and other connections are done correctly.
Regards
hmani