I want to change a 3 prong receptacle (2 hots, 1 neutral) to an L14-30 receptacle (2 hots, 1 neutral, 1 ground). This is a 30amp 240v circuit.
The box currently has no ground wire coming into it. Am I correct in assuming I can just add and attach a ground wire to the metal box and insert into the appropriate terminal in my new L14-30? Thank you!