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How to wire incandescent light fixture with black and white wiring is it wired to ground?

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August 27, 2009 4:57PM

== == === === By asking this question you are probably not quite ready to take on this particular task.

The correct answer to your question will depend on the exact location of the light fixture, its voltage and its power rating. <><><> Whatever is going on, your present wiring situation is not just confusing, it is dangerous. The bare wires are not meant to carry current. They are not coated, and thus have no insulation to protect surrounding material from the heat created by electrical current passing through the wire. You need to cut the whole circuit off at the breaker box until you can get the situation sorted out. Otherwise, you could have an electrical fire. This is what is wrong. At some point in your circuit, some numbskull (probably not a professional electrician) connected something wrong. The thing about electrical circuits is, the current doesn't know what color wire it is travelling through. It travels just as easily across black, white, red, and bare wires. In fact, there is no real difference between any of the wires, except that the "ground" wire has no coating. Electricians use the coating colors so they can keep track of which is which. So it's really more appropriate to talk about hot, neutral, and ground wires than black, white, and bare wires. All the wires could have the same color coating, and the circuit would still work fine. The problem is, if you were trying to hook something up, you wouldn't know which wire was hot. So someone got smart and color coded the wires. By standard, electricians use the black wires for hot and the white wires for neutral, but only because they assume that everyone else does. If the previous "electrician" didn't, it screws everything up. And that's what happened here. Someone did something that was not according to standards. I would start with the switch box that controls this light fixture. There should be two bundles of wires coming into this box. Each bundle will have a black wire, a white wire, and a bare wire. The two white wires should be connected to each other, but not to the switch itself. The two black wires should be connected to the switch. The switch will have two brass screws on one side. The black wires should be bent into a hook and hooked around those two screws and the two screws tightened. It doesn't matter which is on top and which is on bottom. The two bare wires should be connected to each other, and IF the switch has a green screw at the very bottom, the two connected bare wires should be connected to that green screw. That's how everything SHOULD look. But, it may not be that way, which would explain why your light doesn't hook up correctly. You may have a black wire and white wired connected to the two brass screws, instead of two black wires. You may have a bare wire connected to one of the brass screws. You may have a white wire and a bare wire connected to each other. All of these are no-nos. Anything other than what I described above is unacceptable. Hot and Neutral are reversed. You should not be getting any voltage through the ground wire ... EVER !!

On many light fixtures the black and white colors do not matter, except as a safety standard; it should work either way. Typically, however, the black goes to the tip of the bulb and white (neutral) to the shell, for safety when the bulb is being replaced and the current may be on. If the light fixture has a switch, it should always switch the black (hot) connection.

In your case, the white to ground means that the "neutral" may have been accidentally reversed somewhere with the black (which should never happen), leaving the safety grounding wire as the only connection that will "work." It also could mean that the voltage is still "on" when the switch is off, and a person could be electrocuted by "completing" the circuit even with the switch "off". <><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed. Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.