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Are light switches required to be grounded?
Sunday, December 9, 2018
Light switches have been required to be grounded since the 1999 edition of the National Electrical Code. So any light switch installed since your local AHJ (Authority Having Jurisdiction or, in other words, the building department) adopted the 1999 NEC should be grounded. Because each new edition may take several years to be adopted, it might not have gone into effect in your area until a few years later than 1999.
Confirming grounding is easy with a tic-tracer. If you touch one of the screws on the faceplate with the tic-tracer while the switch is in the “ON” position, it will not be activated if the switch is grounded. The tic-tracer senses the electromagnetic field given off by live alternating-current wires, but the metal parts of a grounded switch will absorb the magnetic field, whereas an ungrounded switch will allow it to radiate outwards and make the tic-tracer sound off. See our blog post How does a home inspector use a tic-tracer (non-contact voltage tester) for safety when doing electrical inspections? to learn how to use one.
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."
An exception is allowed if you are replacing an exisitng switch in an older two-wire (pre-1960) electrical system that does not have a means of grounding at the box. However, an ungrounded switch must have a non-metallic faceplate that is also nonconducting and noncombustible—unless the switch mounting strap is nonmetallic or the circuit is protected by a ground-fault circuit interrupter (GFCI).
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