Does a metal back box need to be earthed?
Correspondingly, does a metal box have to be grounded?
The only requirement is that the application is grounded. Metal-sheathed wiring depends on bonding with the metal electrical box for grounding. Using metal-sheathed wiring with plastic electrical boxes, without taking other grounding measures, severs that ground and is highly dangerous.
Subsequently, question is, how do you ground a metal faceplate? For a metal face plate the earth should be connected to the face plate. The metal backbox is also required to be "earthed" by taking a wire from the earth slot in the face plate to the earth slot in the backbox. This is only required if both lugs (the threads in the backbox where the screw goes) are not fixed.
Also, do sockets need to be earthed?
Fixed wiring devices – including socket outlets – should not be wired with flex. An earth conductor insulated with green and yellow sleeving should be fitted between the earth terminal of the socket and the earth terminal of metal back boxes so that the metal box is earthed.
What happens if you do not connect the ground wire?
The appliance will operate normally without the ground wire because it is not a part of the conducting path which supplies electricity to the appliance. In the absence of the ground wire, shock hazard conditions will often not cause the breaker to trip unless the circuit has a ground fault interrupter in it.