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Old 07-12-2010, 06:47 PM   #1
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Hot white wire joined to neutral wires!


I'm doing some troubleshooting with a couple of switches which are on separate circuits in the same box. I untwisted all of the neutral wires that were bundled together and after testing them I found one that was hot. Is this always a wiring mistake? Should I be puzzled by this?

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Old 07-12-2010, 07:23 PM   #2
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Hot white wire joined to neutral wires!


You most likely have a load imposed on that neutral. Untwisting them while the circuit is energized will make all of `em "hot" except for the one feeding from the main panel.

IF you happen to be dealing with a multi-wire circuit, untwisting the neutrals can cause catastrophic damage downstream to certain loads on one of the circuits.

Switch off the main power, then hook `em back up the way they were ...

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Old 07-12-2010, 07:31 PM   #3
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Hot white wire joined to neutral wires!


There is no way that a hot wire could have been twisted together with neutrals. There would be a direct short and a blown breaker.

There are cases where a white wire can be hot, but it really should have some black tape on it to identify it as hot. An example is a switch leg, to a light fixture, where the hot wire is in the box supporting the light fixture. A standard 3-strand wire (white, black, ground) is used to send the hot wire down to the the switch. When I do it, I connect the white wire to the hot (black) in the fixture box, sending the hot side down to the switch with a white wire (which should have black tape near the end). The wire coming back up from the switch is black, so the fixture is connected to a black hot wire and a white neutral.

Two circuits in the same box is a no-no, unless it's a case of using a shared neutral. In that case, the breakers are linked together or a 2-pole is used, so both must be shut off at the same time. You can supply two circuits with a 12-3 or 14-3 wire, using only one neutral, as long as both the black and red wires are hooked to different phases. If that's not done, then the neutral would carry the amperage from both circuits and fry.
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Old 07-12-2010, 07:38 PM   #4
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Hot white wire joined to neutral wires!


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Originally Posted by dogdutyascetic View Post
one that was hot.
Hot as in it can light an incand. bulb to full brightness or
hot as in Phantom Voltage or
hot as in, in series with a load and 120v?
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Old 07-12-2010, 08:08 PM   #5
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Hot white wire joined to neutral wires!


Thanx for the reply. My voltage tester was definitely giving me the lights on going from one of the neutrals to the grounded box. The other whites were not hot. I'm not sure if it was 120 because I didn't test it with a multimeter. I understand how to use a white wire when running power from the fixture to the switch, but that's not what's happening here. I'm wondering why this didn't trip the breaker then. Very puzzling. Also, I wasn't aware that switches could not be on different circuits in the same switch box. I guess this is a good reason to pigtail into the power of the working switch then and just marret the old hot and tape it up inside the box.

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There is no way that a hot wire could have been twisted together with neutrals. There would be a direct short and a blown breaker.

There are cases where a white wire can be hot, but it really should have some black tape on it to identify it as hot. An example is a switch leg, to a light fixture, where the hot wire is in the box supporting the light fixture. A standard 3-strand wire (white, black, ground) is used to send the hot wire down to the the switch. When I do it, I connect the white wire to the hot (black) in the fixture box, sending the hot side down to the switch with a white wire (which should have black tape near the end). The wire coming back up from the switch is black, so the fixture is connected to a black hot wire and a white neutral.

Two circuits in the same box is a no-no, unless it's a case of using a shared neutral. In that case, the breakers are linked together or a 2-pole is used, so both must be shut off at the same time. You can supply two circuits with a 12-3 or 14-3 wire, using only one neutral, as long as both the black and red wires are hooked to different phases. If that's not done, then the neutral would carry the amperage from both circuits and fry.
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Old 07-12-2010, 08:23 PM   #6
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Hot white wire joined to neutral wires!


Why would there be a load imposed on the neutral exactly? I don't understand what you mean by this. Do you mean that the neutral is being juiced by a short circuit? When I untwist them and energize the circuit only one of the whites is hot not all but one. So, I'm not sure what you mean here. Please explain. I'd like to just twist them together the way I found them, but what I found was a mess. I found a junction box with hots from two different circuits joined and a switch which I could shut off with one breaker but is still hot! Oh yeah! Disconnecting these junction box wires is not related to the switch. So there's likely some buried boxes or whatever that's making both wires live at the same time. Thanx

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You most likely have a load imposed on that neutral. Untwisting them while the circuit is energized will make all of `em "hot" except for the one feeding from the main panel.

IF you happen to be dealing with a multi-wire circuit, untwisting the neutrals can cause catastrophic damage downstream to certain loads on one of the circuits.

Switch off the main power, then hook `em back up the way they were ...
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Old 07-12-2010, 08:29 PM   #7
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Hot white wire joined to neutral wires!


Excellent questions. I didn't put a multimeter on it so I'm not sure. How would I test for phantom voltage?

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Hot as in it can light an incand. bulb to full brightness or
hot as in Phantom Voltage or
hot as in, in series with a load and 120v?
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Old 07-12-2010, 08:33 PM   #8
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Hot white wire joined to neutral wires!


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Originally Posted by dogdutyascetic View Post
Excellent questions. I didn't put a multimeter on it so I'm not sure. How would I test for phantom voltage?
http://www.diychatroom.com/attachmen...re-diagram.jpg

An incand. lamp will drop a Phantom Voltage to almost zero.

Be careful.
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Old 07-12-2010, 08:41 PM   #9
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Hot white wire joined to neutral wires!


Interesting. Are you saying that this circuit may have branched but neutral wires may have been excluded? Could this cause a neutral to show as hot when putting a voltage tester on it?

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Originally Posted by Yoyizit View Post
http://www.diychatroom.com/attachmen...re-diagram.jpg

An incand. lamp will drop a Phantom Voltage to almost zero.

Be careful.
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Old 07-12-2010, 09:01 PM   #10
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Hot white wire joined to neutral wires!


This is NOT a case of a switch loop.

A load on the neutral means you disconnected the neutral but left the hot connected. Voltage is still flowing on the hot wire, through the load, and into your now disconnected neutral. The load will not be active since the circuit is no longer completed.

Sorry, but one of the dumbest things you can do is disconnect a neutral with the power on and a load on the circuit, especially if it is a multi-wire circuit as KB stated.
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Old 07-12-2010, 09:10 PM   #11
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Hot white wire joined to neutral wires!


Since we have a licensed electrical contractor commenting, please explain when it's appropriate to use a black wire, twisted together with several white neutrals. I can't think of an appropriate situation.
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Old 07-12-2010, 09:47 PM   #12
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Hot white wire joined to neutral wires!


Agreed it's not a switch loop. The rest of what you say is very interesting. I understand you as saying that a neutral has been disconnected downstream while the load is still connected. I personally can't see how there would be any current in a disconnected neutral wire even if its load wire were still connected. Wouldn't you just have a hot load wire and no current on the neutral? Please explain. I agree that it would be a pretty dumb thing to do. This is only one of many dumb things I've found in an old house, probably one of the less dumb ones actually.

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Originally Posted by Speedy Petey View Post
This is NOT a case of a switch loop.

A load on the neutral means you disconnected the neutral but left the hot connected. Voltage is still flowing on the hot wire, through the load, and into your now disconnected neutral. The load will not be active since the circuit is no longer completed.

Sorry, but one of the dumbest things you can do is disconnect a neutral with the power on and a load on the circuit, especially if it is a multi-wire circuit as KB stated.
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Old 07-13-2010, 06:50 AM   #13
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Hot white wire joined to neutral wires!


It is acceptable to have more than one circuit entering a box but here you keep the neutrals for each circuit separate.

There must be exactly one path back to the panel for each neutral (and one path for each hot). And the neutral must follow the path of the corresponding hot. (Might not be true of really old knob and tube house wiring)

Do not undo neutrals unless the power is off. Now that you have it taken apart, you really should figure out how many circuits are entering the box, and separating out the feed and continuing neutrals for one circuit and marretting (wire nutting) them back together, separating out the feed and continuing neutrals for another circuit if any, etc. Also separating out the feed and continuing hots for each circuit if more than one. If there was only one bundle of colored wires coming in and when taken apart and the power turned on for a moment only one of the ends was hot, then you you have just one circuit feeding the box.

If you left the power on in an ordinary* circuit, and there was a light (or appliance) still switched on, and you undid the neutral, you will see a spark, the light will go out, and the neutral coming back from the light will show hot when you applied volt meter probes to it and to ground (or to the neutral wire continuing on back to the panel). Once the connection is broken (any circuit is broken), the current drops to zero* (amps) but the voltage measured across the break is the full 120* or so.

If you turned off the light switch, you will no longer measure the loose neutral wire as hot (except for possible phantom voltage).

When wiring up a switch, always use a colored wire (not green) from the switch to the black wire or gold screw (hot side) of the light fixture. In a typical switch loop setup, the white wire in a pre-made cable going down to the switch will be the raw (unswitched) power line and connected to the (black) wire supplying the power up at the light fixture box.

Never wire up a real neutral to a switch although you may find this in really old house wiring.

* Different things may happen in combination 120/240 volt circuits aka multiwire branch circuits where the neutral is disconnected. See other descriptions preceding.
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Last edited by AllanJ; 07-13-2010 at 07:29 AM.
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Old 07-13-2010, 11:24 AM   #14
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Hot white wire joined to neutral wires!


A final question. This is looking like something a licensed electrician should be dealing with, which I am not. In the mean time what's the safest thing other than turning the breaker off on that circuit. I assume disconnecting the hot white from the other whites and marretting and taping it should do as a very short term stop gap until this can be dealt with properly, like a week or so. Does that seem reasonable?
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Old 07-13-2010, 11:56 AM   #15
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Hot white wire joined to neutral wires!


If everything was working properly before you made the change, why are you trying to disassemble the circuit? It still does not sound like you understand what has been explained to you.

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Switch off the main power, then hook `em back up the way they were ...

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