switch loop wiring

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  #1  
Old 03-10-07, 02:30 PM
U
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Post switch loop wiring

This may be a little long but you guys are always asking for more info, trying to get all the details in.

Replacing a wall light fixture (and before I'm chastised about not noting the connections before undoing them - my husband did that while I was out).

I have researched for hours on the internet, mostly this forum. I bought a voltage detector. I've labeled breakers. I bought the book, "Wiring 1-2-3" from Home Depot. (I've seen "Wiring Simplified" recommended on this site, hopefully this one is comparable.)

This fixture is operated by two switches (one at top and one at bottom of stairs). (There are other lights / outlets on this breaker.)

Coming out of the wall where the fixture goes are 3 sets of wires, 1 each of black, white and ground (bare copper). The new light fixture also has 3 wires: black, white & copper.

Following the guidelines I pulled from another thread: "The power feed is the black / white pair that makes the light on all the time. The switch loop is the black / white pair that makes the light not work at all. So, now
  • Connect the black wire of the power feed to the white wire of the switch loop. Neither of these wires connect to the fixture.
  • Connect the black from your fixture to the black from the switch loop.
  • Connect the white from your fixture to the white from the power feed.
  • Connect all grounding wires.
That's it. It'll work. I guarantee it.

I've tested the wires to find the power feed. (In this set of wires only the black wire tested hot. The white one did not. Is this correct?)

I have all the ground wires together with a wire nut.

My main question is: Since there are two switches that operate this fixture, are there two switch loops?

If so, my understanding is that I would proceed by:

- connecting the black power feed wire to the two white wires from the switch loops

- connect the black fixture wire to the two black wires from the switch loops

- connect the white fixture wire to the white power feed wire

So, am I close?

Thanks for all your help. Love this web site.

(One more question, can you tell me how to get my husband to STOP trying to fix things?)

Ursula
 
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Old 03-10-07, 02:37 PM
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(One more question, can you tell me how to get my husband to STOP trying to fix things?)
=====================

yes, when he really messes something up, call a contractor but talk to the contractor ahead of time and have him say "if you would not have messed with this (whatever) before you called me, it would have been a LOT less expensive to repair it."
 
  #3  
Old 03-10-07, 02:42 PM
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Your husband should not have undone any wires except those that go to the light. Undoing the other is what caused the problem.

Power needs hot wire and a return wire. The hot wires are usually black and the returns are usually white.

For now ignore all bare ground wires. They get connected together and connected to the metal boxes but they do not (under normal operation) carry current. Discussing them further just makes things harder for some people to follow. When you are all done, they need to be connected.

At the light you have three sets of wires. One set of wires brings power into the box. One set of wires is the switch loop. The third set of wires takes power to some other are of the house.

Determine which is which with your tester. The power wires are the black and white pair that light the tester. To figure out which are the switch loop and which are the wires to the rest of the circuit, connect the power wires to one other set, black to black and white to white. If all the other items on this circuit work, then you know that you have found the wires that feed the rest of the circuit. If not, try the other set.

The switch loop consists of two wires that take power to and receive switched power from the switches. The two switch loop wires (a black and white pair) will go to one of the switches. From that switch there will be three wires to the other switch. Look in your book for a discussion on three way switches and a wiring diagram, so that you learn how a three way switch works, and why two different switch loops (as you proposed) won't work to control the light from two different locations.

Once you know all the wires, connect as follows at the light:

Connect the power black wire to the switch loop white wire and to the black wire that feeds the rest of the circuit.

Connect the white power wire to the white light wire and to white wire that feeds the rest of the house.

Connect the black switch loop wire to the black light wire.
 
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Old 03-10-07, 02:50 PM
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You said that this fixture is controlled by two switches. You also said that there are three black/white cables at the fixture.

You might not have a switch loop at all. Use a circuit tester to see if the voltage on one of those black/white pairs is controlled by the switches. If so, you have no switch loop.

Fire your husband. His carelessness made your job at least ten times harder than it had to be.
 
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Old 03-10-07, 02:53 PM
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The three way switches only need three wires between the switches.

I suspect two wires to the first switch and then three wires from the first switch to the second switch.
 
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Old 03-12-07, 05:41 PM
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Smile switch loop wiring - update

Well guys, I did it! I want to thank all of you for your replies. Racraft, followed your directions and I finally got there.

Thought I'd share and give you all a little chuckle. I was meticulous in everything I did, Re-reading and rechecking everything at least 3 times. I have a healthy respect (if not a bit of fear) for electricity and was overly cautious.

I finally got everything hooked up yesterday afternoon and tried it. I flipped the light switches and it didn't work. The circuits to the other fixtures/outlets in the house did work. At that point I was just frustrated and couldn't figure out what I had done wrong. I turned the breaker back off and had to walk away from it.

All evening I kept going over it in my head. I knew I had followed the directions correctly. Was sitting in bed last night - still trying to figure it out when my husband (yes, the one made it worse to begin with) said, "Did you turn the switch that is on the fixture?" NO. I jumped out of bed, flipped on the breaker, turned the fixture switch and it worked. Unbelievable. Scary to think I worked on something electrical, huh? I was just so focused on all the details of the wiring, it never occurred to me.

So, my husband has redeemed himself (slightly) and has promised he won't repeat his behavior. It took a long, long time to do this simple task but I do have a great sense of accomplishment. Don't think I'll be taking on another electrical project anytime soon. But I did think maybe next week I'd try my hand at open heart surgery. Know where I can pick up a good instruction book?!

I have a much higher appreciation for the work electricians do. Electricians ROCK!!! Thanks again and have a good evening.

Ursula
 
  #7  
Old 03-12-07, 07:11 PM
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I am glad that you sorted your problem out, and glad that I could help.
 
 

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