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I'm installing a brand new motion activated security light to an existing box on my garage. After removing the old light, I notice it only has white/black wiring while the new light fixture has of course white/black/green (ground) wires to attach. What do I do if no ground wire is available with the old box?

  • Have you tried searching the site? I'm pretty sure this has been answered many times before. – Tester101 Jan 19 '16 at 17:34
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There's a few options.

No grounding conductor

If there's no grounding conductor at all, there's a few things you can do.

Install a grounding conductor

Obviously, you could install a grounding conductor for the circuit.

Share a grounding conductor

Code allows you to share a grounding conductor from another circuit, as long as the grounding conductor is properly sized.

GFCI protected

If you're replacing a fixture, you don't need a ground if the outlet is GFCI protected.

National Electrical Code 2014

Chapter 4 Equipment for General Use

Article 410 Luminaires, Lampholders, and Lamps

410.44 Methods of Grounding. Luminaires and equipment shall be mechanically connected to an equipment grounding conductor as specified in 250.118 and sized in accordance with 250.122.

Exception No. 3: Where no equipment grounding conductor exists at the outlet, replacement luminaires that are GFCI protected shall not be required to be connected to an equipment grounding conductor.

Grounding via conduit or cable covering or ground in box

At times, metallic boxes are grounded using metallic conduit, or the outer covering and/or internal bonding strip of armored cable. If this is the case, then the box may actually be grounded.

There's also a chance that there's a grounding conductor stuffed in the back of the box.

Extend the grounding conductor

If the box is grounded, you can simply connect a grounding conductor to the box. If there's a grounding conductor stuffed in the box, you can simply connect to it.

  • If there is no ground available (because it wasn't required by code when it was installed), is it acceptable to install the fixture without a ground, or does code require that it be grounded? – Johnny Jan 19 '16 at 17:56
  • @Johnny No. A new fixture must be grounded. There are exceptions for replacement fixtures, but not for new installations. – Tester101 Jan 19 '16 at 18:17
  • I think this is a replacement fixture, he said he removed the old light and didn't find a ground wire. – Johnny Jan 19 '16 at 23:07
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    @Johnny Sorry I missed that. I've updated my answer. – Tester101 Jan 20 '16 at 2:13
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The box might be grounded on the back. If there's any slack in the cable you might see a ground with a flashlight. I usually wire-up & screw-in an outlet so I can put my outlet tester on to confirm or deny a ground.

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