The recent addition of the GCM test and the UL mandated "just in time" GFI self-test just before turning the power on to the EVSE variant has caused a little bit of havoc with the GFI.

As a result of this, the standard design has changed to include a separate GFI coil for each car. The self-test wire takes one wrap around each coil - which means that the wire passes through each coil twice. That should mean that the fault current from both coils would be required for the self-test to trigger a fault and therefore pass.

The two coils are wired in parallel. The current sensed by each is effectively summed and fed into the burden resistor and the rest of the GFI sense circuit.

Placing the GFI on the load side of the contactors will guarantee that the GCM leakage current has no impact whatsoever on the GFI.