Ceiling Fixture Still Energized With Switch Off

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  #1  
Old 09-25-04, 06:26 PM
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Josdek
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Ceiling Fixture Still Energized With Switch Off

Hello...I removed an old ceiling fan to put in a new one. This is in an older (1940's) home with ungrounded boxes/outlets. I discovered that with the wall switch in the off position there is still enough energy between the hot and neutral to light a neon circuit tester. This is true for two different ceiling fixture/wall switches on the same circuit. Replacing the wall switches did not resolve the problem. Any input on this issue would be greatly appreciated, I am at a stop with the work until it can be resolved. Thanks!
 
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Old 09-25-04, 06:45 PM
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Did you completely remove the switch{es} before you tested for power at the ceiling? The switch may be bad {stuck closed}, allowing current to travel even with the switch off.
 
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Old 09-25-04, 06:48 PM
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DUH!!! Sorry I didn't read the entire post {sidetracked}.Where does power come in,at the switch or at the ceiling?
 
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Old 09-25-04, 07:15 PM
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Thanks for responding. Both switches (for two seperate lights) only have two wires in the box, so I'm assuming the power comes into this circuit at one of the ceiling boxes. I'm not certain where the circuit begins and ends though.
 
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Old 09-25-04, 08:53 PM
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Then you have no problem. Your situation is a perfect example of why you must shut off the circuit breaker when working on a fixture, rather than trying to rely on the wall switch alone.

You didn't ask how to make the connections at the ceiling, but I'm guessing that this is your real question. Is it?

You have a switch loop. I'd like to tell you to install the wire the new ceiling fan just like the old one. But I'm guessing that it's too late for this advice. Is that true?

How to make the connections depends on how you want it to work, and how many wires of each color are in the ceiling box. So please provide this information. The operational options are:
  1. The ceiling fan has no light kit, so the wall switch should just operate the fan motor.
  2. The fan came with a remote control which will be used to control it.
  3. The wall switch should operate only the light kit, and the fan motor will be controlled by pull chains only.
  4. The wall switch should operate both the fan motor and the light kit at the same time.
 
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Old 09-25-04, 09:06 PM
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This would be normal josdek, you are testing for power on the line side of the switch, the switch hasnt come into play yet. Sounds like you have a switch loop. Is there something you need besides this?

Sorry didnt check to see if anyone was replying
 
  #7  
Old 09-26-04, 07:16 PM
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John and Roger,

Thank you very much for your replies. I have not wired it yet, was waiting for your replies. I'm astonished if that's not too strong a word that it's normal there is still detectable power between the hot and neutral with the wall switch off. It's a learning experience. John, I'll be fine from here, the wall switch controls both the fan and the motor. We know which one is hot so I'll wire it according to the instructions. Thanks again.

Joe
 
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Old 09-26-04, 08:43 PM
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Joe, I'm guessing that there are two black wires and two white wires at the ceiling. Is this true? If so, you should know and understand that only one of those two white wires is a neutral. Do you understand what this means?
 
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Old 09-27-04, 04:13 PM
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John,

The wiring is all cloth so there are no colors, I determined the hot by checking it against a ground (run up from the basement, the box is not grounded). There are 2 hots and at least 2 neutrals, the hots are tied together and the neutrals are tied together. I do not know what this means....
Thanks! Joe
 
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Old 09-27-04, 04:25 PM
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What wires are connected to the light?
 
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Old 09-27-04, 05:26 PM
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If you have four wires in the box, it would be unusual to have two hots and two neutrals. One way that this might possibly be the case is if the wall switch is controlling multiple fixtures. However, given your original post, we theorized that you had a switch loop. If so, those four wires would be one power feed, one neutral, one wire carrying unswitched power to the switch, and one wire carrying switched power back from the switch.

However, since you asserted that there are only two wired in the switch box, it makes the switch loop explanation much more likely.
 
  #12  
Old 09-27-04, 08:44 PM
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John,

I have not heard of the term "switch loop" before your post. Is this a bad thing, is it a sign of a problem, or is it just a way houses used to be wired?

Thanks for all your help.

Joe
 
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Old 09-28-04, 12:08 AM
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A switch loop is not a bad thing. It's a commonly used wiring method in modern homes and is perfectly safe. It's one of the first things I learned about here when I starting rewiring my house. I'll try my best to describe it but you can go to a home depot or lowes and browse one of the wiring books on the rack and find a diagram that will illustrate it much better.
Switch loops are used when the switched fixture is located in between the power source and the switch. That might sound a little counterintuitive at first so bear with me. A "standard" switch arrangement on a simple circuit would be to have an incoming romex cable coming in with 3 wires, black(hot), white (neutral), and a bare ground, and an outgoing cable with the same 3 wires going to the fixture. The hot wire from the incoming power supply is attached to one side of the switch and the outgoing hot wire is attached to the other side of the switch. The neutrals would be attached together bypassing the switch using a wire nut. The wires from the outgoing cable are then attached to the fixture. With a switch loop the arrangement is a little different. The first thing you'll notice with a switch loop is that a black and white wire are connected to the switch. The white wire should have a piece of black tape on it indicating it's actually a hot wire in disguise but there is probably just as good a chance that it doesn't though. Now visualize the same incoming power supply wire as mentioned before, in a switch loop arrangement this wire will go to the fixture first (say a light). The neutral (white) wire will be attached to the fixture here. The incoming hot wire will now be attached to the white wire in another 3 wire cable (the switch loop) via wire nut, in effect bypassing the fixture. The switch loop cable then extends to wherever the switch is located. The white (hot) wire is then attached to one side of the switch and the remaining black (hot) wire goes from the switch back to the fixture where it is attached.
Note that it doesn't really matter when bypassing the fixture with the switch loop whether the incoming hot wire is connected to the black wire or the white wire of the switch loop as they are essentially the same wire cleverly extended. Although the proper way is to black to white at the fixture and both ends of the switch loop white wire should be labeled as black. Switch loops are used as it is not always practical or easily achievable to locate a switch between the supply and the fixture.
I hope that helps and as I said it's much easier to understand if you can look at a simple wiring diagram of a switch loop.
 
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Old 09-28-04, 03:02 PM
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Phiilyguy and John,

I want to make sure I'm being crystal clear about this. I understood what Phillyguy described, seems pretty straightforward. When I removed the old fixture there were two wires hanging down which powered the fixture, a hot and a neutral. There are other wires way up in the box but I did not do anything with those. The two wires hanging down still have some power to them with the wall switch off. With the switch on they have the full 120V. As I now understand a switch loop there should not be power at all between the hot and the neutral to fixture with the switch off, or am I misunderstanding this? Thanks again.
 
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Old 09-28-04, 08:03 PM
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With the switch on they have the full 120V
The two wires hanging down still have some power to them with the wall switch off
Firstly are you using a digital multimeter to test for 120v?

I ask this because you say you are only gettting some power, as in less than 120 v. If you are using a digital multimeter any reading significantly less than 110v, say something like 15v or 60v is a false reading. It's beyond my understanding to explain it but it's called "phantom voltage". There's several threads about on this board that are a good read if you have the time.

If you shut off the breaker and attach a light bulb does it light up when the switch is off?
 
  #16  
Old 09-28-04, 08:26 PM
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If I shut off the breaker there's no power at all. With the breaker on, wall switch off, there's enough power to dimly light a test lamp, one of the small, standard neon-type lights with the two probes. Turn the wall switch on and there's normal full power, as would be expected. It's the idea that the neon light will light a little with the switch off that worried me.....
 
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Old 09-28-04, 08:29 PM
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Phillyguy, just realized I didn't directly answer your question. With the wall switch off (breaker on), no, it does not light a regular light bulb.
 
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Old 09-28-04, 09:41 PM
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I would shut off the breaker and replace the switch.
 
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Old 09-13-06, 06:00 PM
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reviving an old thread

i've got the same problem in a 100 year old house.

overhead light receives enough voltage to barely light the bulbs when switch is in off position. with breaker off, no voltage to switch or overhead light.

two wires, one hot, one neutral.

replaced two pole switch, no change.

overhead light still receiving small voltage when switch is off.


i haven't been able to find an answer in my searches here, any additional input about this problem would be greatly appreciated.
 
  #20  
Old 09-14-06, 04:31 AM
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I've seen a similiar set-up a lot of times in older homes. On those the switch was breaking the neutral to the light fixture.
It used to be a pretty standard way to install lighting fixtures.
The voltage that I was seeing with the switch off was caused by continuity (or inductive coupling of the conductors) through the switch (with it turned off).
This set-up had the hot wire directly connected to the light fixture and the neutral traveled from the ceiling box, thru the switch and back to the light fixture. The circuit showed 120V potential between the two wires that connect to the light (even with the switch turned off), but very little current flow. Not enough to power the light.
As another poster said, it's a good example of why to turn the breaker off before working on a circuit.
I don't know if this is the same installation as the original poster has, so this post is for reference only. Use the information at your own risk. 120V can kill you DEAD.
steve
 
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