OpenEVSE performs a self test of the safety features by checking for the presence of voltage on each line using Optically Isolated detectors connected to the AC_Test terminals. The Earth ground check is performed during Power on Self Test (POST) if Service Level is set to "Auto" and at the during each charge session.
For information on GFCI Errors see: GFCI Error
Theory of Operation:
The two AC line monitor chips act as opto-isloators. The presence of an AC voltage potential relative to ground on either L1 or L2 will result in a state change from High to Low appearing on PD3 and PD4 of the Microprocessor.
The circuit tests both stuck relay (voltage present when there should be none) and continuity to Ground (voltage present when it should be). Stuck Relay is tested whenever the relay is open and Ground is monitored when the relay is closed.
Troubleshooting:
If the display reads "ERROR NO GROUND":
- Verify the AC_Test Headers are connected to each line on the load (J1772 cable) side of the relays/contractor.
- Verify the OpenEVSE board is connected to Earth Ground with the AC Input Ground, J1772 Ground and Chassis Ground (if applicable)
- Verify the relay/contactors are activating