Another 3-way switch issue

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  #1  
Old 01-22-21, 06:53 PM
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Another 3-way switch issue

I've had a 3-way switch in use for 13 years with no problems other than some LED bulbs glowing when off. I always figured it was due to phantom voltage or cheap LED bulbs.

Today I was changing a bulb with the switch off and as I brushed the recessed lighting can with my knuckle, I got a shock. I thought it was odd, so with the power still off I measured the voltages at the socket. Here's what I got:

Switch off (no power):
Hot-ground: 120V
Neutral-ground: 120V
Hot-Neutral: ~0V

What the !@#$%?

With the switch on (power to the lights), I get what I expect to get:
Hot-ground: 120V
Hot-Neutral: 120V
Neutral-Ground: 0V

It appears that with the 3-way switch off, the neutral and hot are both hot, so the switch still functions correctly. Yikes, this can't be safe even though it's been wired this way for at least 13 years (since I moved in).

It's too dark to work on anything until morning. Tomorrow, I'll kill shut off the breaker and try to figure it out. The switches each have a black, blue and red wire (no ground at the switch). I only see a white neutral in the back of one box, so I'm guessing this is the "load" side. Any ideas as to how it got wired this way?
 
  #2  
Old 01-22-21, 07:08 PM
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Sounds like an open ground. Neutral and ground should always be at the same potential. They are connected to each other in the panel.
 
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Old 01-22-21, 07:16 PM
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Somehow the neutral is being switched in that circuit.
Sounds like a conduit system which means grounds should be ok.

If you need further help from us.... tell us what colors are on each switch.....
in particularly which color is on the dark/black common screw.
 
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Old 01-22-21, 07:44 PM
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Thanks.

I'll investigate tomorrow and take some pictures if I can't figure it out.

I'm trying to envision how the neutral and hot could both be hot when the switch is off but still work correctly when on.
 
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Old 01-22-21, 07:50 PM
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The neutral should always be on the light and the hot gets switched.
So if the power/hot is always live to the light and the neutral is switched..... the power will flow thru the filament and down the neutral wire which is sitting there open/not connected.

Make sense ?
 
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Old 01-22-21, 09:07 PM
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I think I understand that.

So hot is wired to the lights and the 3-way switch is opening/closing the neutral. The would explain why hot and neutral (at the light) are both 120V relative to ground when the switch is off.

It also explains why I got a shock and possibly why the LED bulbs glow when off.

It is probably a neutral wire connected to common of the first 3-way switch with hot wire running continuously to the lights, correct? The 2 travelers should be fine as-is.

If I don't see the hot in the switch box, is there anything that can be done?

 
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Old 01-23-21, 05:40 AM
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You will need to find out where the power comes in, whether to the first switch, to the second switch, or to the light fixture.

From where the power comes in the white neutral should continue to the light fixture as all white wiring not connected to any switches.

It is possible for other white wires to be connected to switch terminals but not to the incoming power whte neutral. Put bands of black tape around both ends of each of these other white wires you see, if any.

The light can work perfectly well with hot and neutral exchanged and/or neutral connected to switches except it is easier for someone to get electrocuted accidentally int he manner you got shocked as y ou described.
 
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Old 01-23-21, 12:13 PM
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Upon further investigating, it looks like only the neutral was run to the switch box. I suppose I could try to go into the attic to find the junction box and switch the hot and neutral, right?

Was this common in the 1940s? I can't figure out why it was done this way. Other than the obvious "hot is hot when the switch is off" (and warning people when they change a bulb) is there any other major concern here?
 
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Old 01-23-21, 07:11 PM
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The switches each have a black, blue and red wire (no ground at the switch)
This is NOT typical 1940's wiring. There would not be blue. That's why I mentioned conduit.
If it's not conduit then it's four wire cable and there should be a white.

I don't know why just neutral would be run to the box.
It sounds more like someone mixed up old wiring where it was hard to determine which was white or black and picked white instead of black to switch.

We're not going to be able to help much with this. It will take investigating.

I'd be concerned with the wiring. Is it a major concern..... like unsafe..... I'd say borderline.
 
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Old 01-24-21, 06:41 AM
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First, thanks so much for responding and helping me. I'm such a beginner here that I don't even know what I don't know.

Here's how I believe it's wired based on what I see in the switch box and my multimeter readings. I could shut power off at the breaker and verify if it would be helpful. I don't see any ground wires in switch box #2 but I do see a one black wire terminated with electrical tape (not shown below).


 
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Old 01-24-21, 11:21 AM
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Your diagram appears to match what you have.
I'm still trying to figure out where the blue wire is coming from.

Possibly you have knob and tube wiring and someone just ran two pieces of wire.... red and blue.
 
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Old 01-24-21, 11:42 AM
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Possibly you have knob and tube wiring
It is not unusual to find neutral switching on K&T wiring. So that may be a hint as to what is going on. Look for exposed K&T wiring in the attic or basement.
 
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Old 01-24-21, 01:36 PM
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I had to look up K&T wiring but I don't think I have any of that in the house. The previous owner upgraded a new 200A panel 15 years ago and, for the most part, upgraded all the wiring, switches, receptacles, GFCI, etc. There are old electrical boxes in the wall but I think he didn't want to repair the lathe and plaster walls.

It's not easy for me to access the attic and crawlspace, but I see "newish" white and yellow romex where it's visible. Some of the wiring in the boxes looks older than 15 years. Is it possible they left some of that there where it wasn't easy to upgrade without opening up the wall?

Before I had a multimeter, I would only turn the switch off before replacing a fixture. But after a couple of shocks and a few pops, I started shutting off the breaker before doing anything. I only recently got a multimeter but this experience has explained a lot. I'm trying to figure out why anyone would have put the switch on the neutral unless the previous guy DIY'ed that way. He was from the UK if that's relevant.

If it's wired as I have it shown, is it relatively safe for now? Or should I get an electrician out asap.

Again, my tremendous appreciation for your patience.
 
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Old 01-24-21, 01:41 PM
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As long as you are aware that the light fixture is not dead when the switch is off there is no harm.
 
  #15  
Old 01-24-21, 04:09 PM
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It is easy enough to fix by reversing the L1 and N connection.
 
  #16  
Old 01-30-21, 02:48 PM
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Sounds you have a neutral to ground situation.
 
 

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