Personally, I feel that too much emphesis is placed on the fact that a relay can fail. So do earth leakage relays. I replace on average 2 each week....
Thank you Isetech, I did consider that but would like to use fire retardent cables if possible, the batteries and inverter are just below and should...
For any of your protective components to operate on an earth fault, your neutral and earth must be at the same potential, so I would suggest earthing...