To diagnose this fault condition follow these steps:

1. Disconnect all cables connected to the panel and supply it only through the batteries.
2. Wait about 5 minutes and check the earth leakage fault persists.
3. Check the tension between the Earth and ground. This value must be found between 6V and 7V DC, if not, the motherboard needs to be inspcted at GFE.
4. If the test of section 3 has been satisfactory connect the main power 230 VAC and repeat the test of point 3, if the value is out of limits the problem is in the mains power supply.
5. Connect a pair of cables (+/-, in/out, etc) to the panel at a time, repeating the test of point 3 until the measured voltage is not correct, then you have found the location of the fault.
6. Locate the cause of the failure by checking the possible causes listed related FAQ.