3 sets of wires coming into light/junction box, confused

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Old 02-06-06, 07:20 AM
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3 sets of wires coming into light/junction box, confused

Hey guys,

So I have this junction box on the ceiling in my basement which runs a single light in the center of the room, the wiring is confusing to me though. each wire of course has black, white, and ground. Two sets of the wires are twisted together as usual, but the rest is strange. The black wire from the light is twisted to the white wires, then the white wire is twisted to the separate wire that runs to the switch on the wall (twisted to white), then the black from the light switch is twised to the white ones in the box, and everything is grounded. Does this make sense? I've seen it before where power is supplied to the junction box and a red wire is used to do the switching, but I've never seen this. I need to undo all of this, install 4 pot lights, and run them off the same switch.

thanks
 
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Old 02-06-06, 08:34 AM
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What you described in a switch loop. It is common in switch loops to find white wires connected to black wires.

The exact way you described it is not quite right, but I'm guessing that the flaw is in your description or my interpretation rather than in the wiring.

The typical switch loop wiring is to connect the switch cable white wire to all the black hot wires in the box. Then the switch cable black wire is connected to the fixture black wire. Finally, the fixture white wire is connected to all the white wires in the box except the switch cable white wire.

You description almost, but not quite, matches what I described above.
 
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Old 02-06-06, 11:41 AM
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thanks for the reply John. Is this the most effective way of wiring the light, or is there a better/safer way of wiring it?

thanks
 
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Old 02-06-06, 05:46 PM
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All legal wiring methods are, in general, equally good. Factors such as topography sometimes suggest one way or another.
 
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Old 02-06-06, 09:17 PM
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Switch loops can sometimes save wire or be an easier choice, if for instance you want to pull one wire cable instead of two. As you see they can be more confusing.
 
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Old 02-07-06, 12:20 AM
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neutral wires (i.e., the "white" wire) used in a switch-loop really should be coded black/hot. Generally, this is done by either wrapping a piece of electrical tape around the white wire, or by coloring a portion of it with a black marker pen. Doing this helps reduce confusion.

Like others have said, switch loops are completely safe and acceptable. They can make things much easier, reduce costs (labor and materials), and reduce congestion in the electrical box.
 
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Old 02-07-06, 06:18 PM
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The white wire in a switch loop should never be referred to as a "neutral". It is simply a white wire that is hot. Not all white wires are neutrals, and this fact confuses a lot of people.

Tape tends to fall off. Use a black marker.
 
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