GFCI tripping due to hot neutral

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  #1  
Old 02-07-08, 08:01 PM
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GFCI tripping due to hot neutral

I am in the process of replacing all switches and receptacles in a house I just purchased. I started with the GFCI's in the master bathroom. Installed, tested, everything seem to work fine. My wife flips a threeway switch located down stairs and it trips one of the GFCI's in the bathroom. I double checked my hot/neutrals, line/loads to be certan it was not a problem at the GFCI's. I than pulled both threeway switches and found that the neutral stemming from the light was going hot when turned on. I pulled the bulb out and the neutral remained neutral. The Hot to the bulb is working correctly but the bulb is not turning on and the neutral is going hot whenever the bulb is supposed to be on. I have not pulled the light housing yet but it sounds like a short in the light fixture to me. Do you guys have any input in regards to this problem?
 
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  #2  
Old 02-07-08, 08:37 PM
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Repeat after me three times:

All white wires are not neutral.
All white wires are not neutral.
All white wires are not neutral.

Rewrite your post without using the word "neutral". Just stick to colors. Call a black wire black and a white wire white. Don't try to infer purpose when such inference may not be correct.

A three-way switch does not have an "on" and "off". It merely has an "up" and "down".

In what city do you live?
In what year was the house built?
 
  #3  
Old 02-07-08, 09:29 PM
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Thanks for the reply John.

House was constructed in 77. Located in Houston, Tx.

I purposely did not make reference to any colors. I identified the neutral as such because it is wired to the neutral block in the circuit box.

In black and white.

Box 1:
Black (Hot)
White (Up)
Black (Down)

Box 2:
Black (to load)
White (down)
Black (up)
White (twisted pair, one from light, other goes to GFCI box)

Concerning Box 2:
With the bulb insterted and the Black in box 2 hot, the white twisted pair are hot and either the black (up) or white (down) are hot. I untwisted the white pair and found that the white coming from the light is hot at the same time as the black going to it. The other white in the twisted pair goes to the GFCI box. This white is never hot once untwisted. If i take the bulb out the white stemming from the light is no longer hot even though the black to the light is hot.

Props to anyone that understands this over my previous post. Simple circuit not so easy to explain.

Any way you put it, the black and white at the light are hot. That same white was wired back to my GFCI (twisted pair in box 2) and is recognized as a short considering the black and white on the GFCI are now hot.

Does this sound like a short in the light fixture?
 
  #4  
Old 02-07-08, 11:23 PM
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For three way switches, you're going to need an extra wire (usually red).

You're replacing the switches and receptacles? Unless you're using a method outlawed before you were born, you need three wire.
 
  #5  
Old 02-08-08, 05:36 AM
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You have an open open neutral connection somewhere between the switch and the panel. Since a GFCI is also tripping I would start there and check all the connections.
The reason the white measure hot and the bulb doesn't come on is because the volt goes through the bulb but does not make back to the panel so no current can flow and light up the bulb.
 
  #6  
Old 02-08-08, 06:43 AM
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Like Fubar says, I'm worried about the wiring of your 3-way switches. Are you sure that they are 3-way switches? Is the switch lever blank, or does it say "on" and "off" on either side of the lever? Does it look like this was professionally wired?

Note that there are several illegal and unsafe methods to wire a 3-way switch, some of which can cause a GFCI to trip. We need to make sure you don't have such a situation.

When you say that a wire is "hot", can you tell us exactly how you determined that? What test device did you use, was it digital or analog, and where did you put the two probes?
 
  #7  
Old 02-08-08, 06:45 AM
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Fubar411,

There is a third wire, Box 1 has 3 wires, and Box 2 has 5 wires. I guess in 77 the electrician chose not to use red. Assume the second black is the red.

Joed,

That makes sense. I will remove the GFCI's again tonight and report my findings. I must have crossed the whites on the GFCI's when I installed them.

John,

I doubt the wiring on this house has ever been tampered with since built. Everything is original. The owner lived there since built and all lighting is original. Fans were never added, all recepicles and switches appear to be original.

Switches are blank but I don't recall ever seeing an "on" or "off" on any rocker switches (only toggle switches). The only way I can confirm they are 3-ways are by the package they came in, the wiring diagram on instructions, and the number of and location of sidewire spots. They may have markings on the back but my eyesight is too poor to see anything.

I used a test light for determining wire state by grounding black probe (bare copper wire) and touched the red probe to wire of question. I tested every wire in each box for every possible switch combination. I also tested the wires at the light. I used an ohm meter to find the two common wires between the 3-ways. This light worked before the GFCI's therefore there must be a problem at the GFCI's.


Thanks
 

Last edited by FluidOne; 02-08-08 at 07:08 AM.
  #8  
Old 02-08-08, 06:51 AM
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Is your house wired with NM cable (what people generally call "Romex"), or is it wired with individual wires in conduit?
 
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Old 02-08-08, 07:31 AM
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Can't swear what the poster has but Houston residential code does not require conduit and at least 99.9% of contractor built houses after 1970 are NM. Wonder if someone used one conductor of an NM cable for the "3rd" wire?
 
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Old 02-08-08, 07:41 AM
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I have little experience with house electrical work so bear with me on this one. I did a search for Romex on the net and found this image.



This Romex apperas to seperate and seal the individual wires. I am inclined to say the I have an older type of NM cable. It's a plastic sheath over the individual wires but the sheath material does not fill between the individual wires as in the provided image.
 
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Old 02-08-08, 07:47 AM
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The absence of a red wire in the wiring of 3-way switches in a cable-wired home is always unusual, often suggesting amateur wiring. It can be correct and safe, but it often is incorrect and unsafe.
 
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Old 02-08-08, 08:33 PM
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I'm working on this mess at the moment. I disconnected both GFCI's and double checked both 3-ways. I coupled all the white wires in the GFCI boxes and flipped the 3-way switch. The light turned on as expected because I now have a neutral.

With all wires in the GFCI box separated I found the one black (hot) and its white (neutral). I hooked up the line in the 1st receptacle and left the load and 2nd GFCI receptacle unhooked. Both whites in each box are still coupled, only now I have one coupled white hooked to the line of the 1st GFCI. Tested the line on the 1st receptacle and tested the light on the 3-way. Everything worked fine.

Left the 2nd box the same (still has the whites coupled). I hooked up the load on the 1st GFCI receptacle which meant I had to decouple the whites. Flipped the 3-way switch and the GFCI tripped. It's obvious I have lost neutral. The white on the GFCI load is now hot.

I tested the side screws on the GFCI and found that the hot terminals are connected but the neutrals are not. Is this typical? Do i need to purchase a different type of GFCI receptacle? These are made by cooper purchased at Lowe's.
 
  #13  
Old 02-08-08, 09:55 PM
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I was forced to wire the GFCIs as indicated in the image on the right.



Otherwise I end up with an open neutral. I guess I lose protection on other outlets using this method. Of course the receptacles tested OK and the 3-ways no longer trip the GFCIs.

I have been frequenting this forum for the last few months and found everything I needed prior to this post. Thanks for all the help and please let me know if this wiring scheme is not recommended.
 
  #14  
Old 02-09-08, 04:28 AM
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If I am understanding your dilema,,,,,you are sayng that the 3 wires you have are not red, black, white, instead are 2 black, 1 white. you need to indentify which on of these black wires on other end are hot, which would be your coomon. You do this, by hooking one black wire at a time up to load side of gfi, and go to other end, and using your tester, determine which black wire is hot. Before you do this, disconnect those black wires, and seperate them before you hook up to load on gfi. After you identify which is hot tag it, so you know which is hot, or common. I suggest you go to either Lowes or Home Depot, and buy the Better and Homes Complete guide on wiring, because they have detailed wiring diagrams on 3-way. You have to get the wiring straight on 3-ways, especially when load, or line feed is coming from gfi. They didn't have gfi's back in the 70's, so it wasn't a concern.
 
  #15  
Old 02-09-08, 07:23 AM
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I think the fact that you mentioned they did not have GFCIs in the 70s is key.

It is impossible for me to hook the GFCIs up using the illustration on the left in my previous post. This leads to an open neutral at the 2nd GFCI.

The Hot line and load side of the GFCI receptacle are connected but the neutrals are independent.

It's almost difficult to miss wire a 3-way when there are only 3-wires in each box. It takes a whole minute to identify the commons. John already emphasized not all white wires are neutrals. I would never assume this nor would I agree that all red wires are common.
 
  #16  
Old 02-09-08, 11:07 AM
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Why are you insisting on wiring the gfi from the line side? Why don't you just wire it the way it is supposed to? line to line,,,,,load to load? ??????
 
  #17  
Old 02-09-08, 02:44 PM
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my house had the same problem

Back in '58, the electrician had picked up a different circuits' neutral for a 3 way lighting circuit in the kitchen. This will trip a GFI or in my case, a AFCI.
 

Last edited by telecom guy; 02-09-08 at 02:45 PM. Reason: mispelin'
  #18  
Old 02-09-08, 10:10 PM
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Kskier, I addressed this question twice in previous posts. The line neutral and load neutral on a GFCI are independent. If the white wire leading to the line is the only neutral how will the white load circuit work? I will not work without the line neutral, therefore; I am forced to couple the whites for the line and load. Maybe newer houses are wired differently, but this is the only way it will work unless I drop new neutral wires. I put together a diagram of the circuit. Notice all white wires are wired to line of each GFCI, otherwise I end up with an open neutral.

 
  #19  
Old 02-09-08, 11:04 PM
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At one of the 3 ways there is probably the power feed and the switchleg going to the light. The white wire is tapped with the power feed in order to bring power to the other 3 way switch. This is acceptable and commonly used in the field. Article 200.7 (C) (2)
 
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