The requirement for grounding is located at 404.9(B) of the NEC, and states that "snap switches, including dimmer and similar control switches, should be connected to an equipment ground conductor." It further says that the switch "shall provide a means to connect metal faceplates to the equipment grounding conductor.". If you have an old light switch that you want to ground, check for a ground screw. If there is not one, it would be a good idea to replace the switch with a newer model. Most modern light switches cost less than $1.00. If you must use that light switch, connect the ground wire to the electrical box. This will only work if the electrical box is.
Unscrewing a switch plate will reveal a number of cables, and, in most modern homes, one of these will be a ground wire. Grounding light switches have become commonplace, used as a preventative safety measure. It is perfectly legal to wire a light switch without the inclusion of a ground. Dimmers will require a ground wire but traditional.. Step 3: Connect Ground Wire. Connect the ground wire to the grounding screw on the light switch. The grounding screw is usually located at the top of most switches and has a green/yellow colored head.