I have installed an EV level 2 charger in my garage. It is a 30 amp charger. It is around 8 feet away from the breaker box. I used 8/2 wire to be on the safe side for future possible upgrades and used a 2 pole 40 amp breaker, as required by the EVSE instructions.
The EV charger is working fine. The question I have is that the two hot wires are 8 gauge but the ground wire is a bare 10 gauge wire. Is this OK or should I replace the ground with an 8 gauge wire?
Yes, a 10 AWG ground wire is fine for up to a 60A circuit.
The 8/2 Romex (NM) cable is good for amperage up to 40 amps. However, the breaker must match the socket / EV charger spec. If the socket is a NEMA 6-30 or 14-30, the breaker must be 30A. If the EV charger docs specify 30A breaker, then that must be so.
Again, the 8/2 cable is perfectly fine for 30A or really any size up to 40A. So if your spec calls for a 30A breaker, you only need to change the breaker. 30A sockets will accept #8 wire.
It is possible that a 30A-nameplate charger might want a 40A breaker. The documentation will tell the tale.
#10 then is only good for 30 amps , correct this before too many people see this
As requested, correcting this: using the chart from https://diy.stackexchange.com/a/151175/18078
