OpenEVSE runs a Self Test of the Ground Fault Current Interrupt (GFCI or GFI) system to detect AC current flowing to ground instead of the proper return path by sending a small current through a self test coil to "tickle" the GFCI circuitry. If the circuit does not detect a fault during the test, OpenEVSE does not allow charging.

For information on Earth Ground Errors, see: Ground

Troubleshooting steps:

  • Check the coil is connected correctly
    • 4 pin from Board Edge - Main coil 1 - Main coil 2 - Test loop - 1 Test loop 2
    • 3 pin from Board Edge - Common (Main coil 1 & Test loop 2) - Main coil 2 - Test loop 1
  • Check that all hot lines run through the GFCI coil
    • Ground and pilot lines should not run through the coil
  • Check Firmware version - versions between 3.7.8 and 3.9.9 used less self test power. 
    • Firmware 3.9.10 restores power level
    • Work around for firmware 3.7.8 - 3.9.9. Swap positions of orange wires by releasing wire from connector with a small object. The retaining pin is exposed in a small window on the connector.

Theory of Operation:

The current transformer coil detects any unbalanced current flowing through conductors passing through it. By passing both of the J1772 power cables through it, any current leaked to ground in the EV will result in a differential current within the CT. This will result in a voltage appearing at the input of the OP amp (diode D1 protects against excessive voltage in a run-away leakage event, such as a conductor short to ground). The second OP amp acts as a comparator and will "switch" from a low output to a high output when a threshold is exceeded. This output is fed as a fault indication into the CPU, which will register a ground fault and open the relay.