Question

Grounding Lighting Fixture: How must they be grounded and with what size conductors? Cite the NEC code

Answer 1

The correct polarity is crucial while grounding because of manufacture equipment safety may defect when connected improperly.

For grounding,

If the light fixture has an external chassis made out of metal, then run a green wire from the 3rd round prong of a 3-prong plug to a grounding screw on the metal chassis. Usually, it’s a green screw. If there is no such screw, you may need to drill a hole through the chassis and supply your own screw. Make sure it will securely hold down the grounding wire to maintain reliable electrical contact. It’s probably a good idea to crimp a loop terminal onto the end of the grounding wire so you don’t tighten the screw down onto the bare threaded strands of the grounding wire.

If the light fixture is made out of porcelain (or some other non-conductive material) and lacks a metal chassis, you won’t be able to ground it. But in this situation, you also don’t need to ground it because there is no shock hazard in touching any of the porcelain in the light fixture base.

In general, “grounding” any sort of electrical appliance simply means connecting a wire from the metal chassis of the appliance to the third/grounding prong of the plug, which of course must be plugged into a properly-wired grounded power outlet (without going through a “cheater” adapter plugged into it). The grounding hole of a properly-wired power outlet should have a green wire running from it too (eventually, not too far away) a grounding rod that’s actually pounded into the ground.

As an additional safety precaution, any appliance with a metal chassis that needs to be properly grounded can be plugged into a special GFCI power outlet. (GFCI = Ground Fault Circuit Interrupter.) If it detects even a small electric current (single-digit milliamps) running from hot to ground or from neutral to ground, it will pop the circuit breaker built into the outlet. Very highly recommended (and required to satisfy electrical code) in kitchens and bathrooms.

For the size of the Conductors

Most lighting circuits are controlled by a 15 amp circuit breaker, and therefore 14 gauge wire is acceptable. Circuits with power outlets are often controlled by 20 amp breakers and should be wired with 12 gauge wire if not you can do like

As an example, you have eight incandescent bulbs, each with a wattage of 100 watts that run through a 120-volt circuit. First get the sum of the wattage of all the five bulbs, which is 800 watts. Then divide 800 watts by 120 to get 6.7. Using the Audel Mechanical Trades Pocket Manual as a reference, you will find that the equivalent rated ampacity rating of the resulting quotient is 15, which would require a 14 wire.