Very often the ground wire in the fixture is ignored, or just connected to the box, if there isn't a conductor to connect to. This, however, is a code violation as any fixture with a ground wire is required to have it properly connected to an equipment grounding conductor back to the panel. This is for YOUR SAFETY. Technically you should rewire the circuit with the proper conductors.
It is BAD PRACTICE to connect the ground wire to the neutral or white wire because this could create a hazard of its own.
If you don't have the wire then you just can't ground it. This should not be too much of a problem. Most light fixtures are not grounded and some don't even have ground wires.
The green wire on the light fixture is a ground wire. If there is no ground wire in the conduit, the green wire should be attached to the metal box with a screw.
The fixture box should have a ground screw on the bottom of the box. Sometimes you have to move other wires out of the way to see it. Just reconnect the fixture ground wire to this screw.
Don't worry about it some fixtures have no ground terminals. just shove the groung wire to the back of the box. Correction, if the fixture is metal and it shorts out, the metal surrounding the fixture could become electrified. That's why fixtures today are normally grounded to their mounting plates and then the lead is attached to the incoming romex. In the past, attaching these plates to metal boxes (either grounded by an incoming wire or grounded to the BX cable) eliminated the need for a ground wire. If the hot wire hit or shorted to the fixture, it would blow a fuse or circuit breaker. Many electrocutions and fires later, the folks at Underwriters realized that even that method of grounding wasn't sufficent (the old aluminum boxes and bx cables were crappy conductors. Solution; (and I practice what I preach because I remodel many old homes) get a little creative and spend the extra time to wrap a little ground wire to a mounting screw, or piece of metal, on the mounting plate of the fixture and then attach it to your incoming romex ground. On an old fixture, it could mean the difference between a fire and a tripped circuit breaker. If you have any metal boxes, old or new, ground to those too. <><><> Connect a pigtail to the metal canopy, and use a wire nut to connect the safety ground to it.
Connect the ground wire to the metal box.
A ground wire is a typically uninsulated copper wire. The intent is to connect the wire to an electrical appliance or fixture to provide electricity a path to ground in the event of a short, thus preventing electrocution.
The bare copper wire is a ground wire. if your old electrical system only has black and white, then you don't have a ground wire to hook the new fixture's ground to. Safest bet is to run a ground wire to that junction box (or hire an electrician to do that). If the box in the ceiling (I'm assuming its a ceiling fixture) is metal, the home's electrical system ground wire may be attached to the metal box itself. If that's the case, you simply need to attach your new fixture's ground wire (the bare copper one) to the metal box. If in doubt -- have an electrician look at it.
I always connect the ground wire to the box. However, if there is no real ground wire running back to the panel it really does you no good. The NEC requires that you rewire the circuit with the proper conductors. Remember that the ground is for your protection. Without a proper ground, you run the risk of injury or death if the fixture wiring fails.
Is this a fluorescent fixture? Most fluorescents will not start if the fixture is not grounded. Make sure the fixture has the branch circuit ground wire properly connected.
Fixture where socket is inserted should be grounded to body
Just install the new fixture with black to black, white to white, and cap off the ground wire on the new fixture. It'll be fine.
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