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Old 07-23-2016, 09:18 PM   #1
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Default Chasing that voltage

Hey folks,

I was on this website a long time ago... couldn't remember my ID or email attached to it though, so here's a fresh question from me.

I installed a chandelier in a kitchen, 100 year old house. I couldn't figure out why there was still voltage on the switch leg coming up even after both switches were off, so here's the facts... I need help understanding why this happened:

1) Dead-end 3-way switch set-up, i.e. the hot sent over to the other switch via Romex 3-wire
2) Both traveler wires from the Romex operating fine, they did their job when the switches were hooked up
(Imagine the light isn't connected yet, since these next 2 voltage readings were taken before the chandelier was wired in.)
3) When the light comes on, there are 120 volts between the "switch leg" and "neutral", which I ultimately connected the chandelier to
4) When the light is off, there are 55 volts, regardless of dimmer.
5) I read the voltage of the box to the "neutral" in a nearby outlet and found 25 volts.

Where is this voltage coming from? I told the homeowner that basically there is a problem with the bonding at the service or something else where the neutral is tied into the ground. I continued to tell him I've been in houses where people got poked because there was about 60 volts touching the yoke of the switch and breaker's not tripping. Since I didn't wire the house, I just noted on the invoice there's a "possibility" of voltage at the dimmer when it's deenergized. That's basically why I spent a ton of time trying to make sure this ancient wiring wasn't going to poke or bite anyone in the house.

Everything worked great when I left. I'm just baffled about the voltage present at the chandelier after the switch/dimmer breaks the circuit. Is it my Fluke T5-600?
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Old 07-23-2016, 09:30 PM   #2
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Welcome to the world of switched neutrals, common neutrals between circuits, and bootleg grounds
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Old 07-23-2016, 09:58 PM   #3
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Welcome to the world of switched neutrals, common neutrals between circuits, and bootleg grounds
There are some people out there who still do this today. Talk to them until you're blue in the face and they're not going to change.
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Old 07-23-2016, 10:03 PM   #4
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There are some people out there who still do this today. Talk to them until you're blue in the face and they're not going to change.
Nooooo ... tell me they all go to a DIY site and get good advice


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Old 07-23-2016, 10:44 PM   #5
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Welcome to the world of switched neutrals, common neutrals between circuits, and bootleg grounds
And a rude welcome it is.
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Old 07-23-2016, 10:52 PM   #6
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D on't

I njure

Y ourself
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Old 07-23-2016, 11:46 PM   #7
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Originally Posted by ~48~ View Post
Hey folks,

I was on this website a long time ago... couldn't remember my ID or email attached to it though, so here's a fresh question from me.

I installed a chandelier in a kitchen, 100 year old house. I couldn't figure out why there was still voltage on the switch leg coming up even after both switches were off, so here's the facts... I need help understanding why this happened:

1) Dead-end 3-way switch set-up, i.e. the hot sent over to the other switch via Romex 3-wire
2) Both traveler wires from the Romex operating fine, they did their job when the switches were hooked up
(Imagine the light isn't connected yet, since these next 2 voltage readings were taken before the chandelier was wired in.)
3) When the light comes on, there are 120 volts between the "switch leg" and "neutral", which I ultimately connected the chandelier to
4) When the light is off, there are 55 volts, regardless of dimmer.
5) I read the voltage of the box to the "neutral" in a nearby outlet and found 25 volts.

Where is this voltage coming from? I told the homeowner that basically there is a problem with the bonding at the service or something else where the neutral is tied into the ground. I continued to tell him I've been in houses where people got poked because there was about 60 volts touching the yoke of the switch and breaker's not tripping. Since I didn't wire the house, I just noted on the invoice there's a "possibility" of voltage at the dimmer when it's deenergized. That's basically why I spent a ton of time trying to make sure this ancient wiring wasn't going to poke or bite anyone in the house.

Everything worked great when I left. I'm just baffled about the voltage present at the chandelier after the switch/dimmer breaks the circuit. Is it my Fluke T5-600?
I'm curious - you said you had 3 wire romex connecting the two 3-ways. Have you considered the possibility of induced voltage? I know this caught me a couple of times early on in the trade - I would measure about 30 (induced) volts on the not-in-use traveller of a 3-wire in a 3-way configuration (in new housing, properly wired). 55 volts is a higher number than I remember ever seeing, but maybe a possibility, or at least part of the puzzle?
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Last edited by Mugs; 07-23-2016 at 11:48 PM.
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Old 07-24-2016, 02:13 PM   #8
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I'm curious - you said you had 3 wire romex connecting the two 3-ways. Have you considered the possibility of induced voltage? I know this caught me a couple of times early on in the trade - I would measure about 30 (induced) volts on the not-in-use traveller of a 3-wire in a 3-way configuration (in new housing, properly wired). 55 volts is a higher number than I remember ever seeing, but maybe a possibility, or at least part of the puzzle?
Good point Mugs
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Old 07-24-2016, 03:42 PM   #9
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Are you reading this voltage with a DMM or with a wiggy type tester? I'd only trust a low hz tester.
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Old 07-25-2016, 10:01 PM   #10
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DMM for the reading.

Yes, 30 volts on the unused traveler. That's part of why I paused and had to come back and finish.. What's it all mean?
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Old 07-26-2016, 02:12 AM   #11
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DMM for the reading.

Yes, 30 volts on the unused traveler. That's part of why I paused and had to come back and finish.. What's it all mean?
Try a low z tester, they eliminate ghost voltages.



A standard DMM can give you false readings.
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Old 07-26-2016, 09:53 AM   #12
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I really need to get one of those.
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Old 07-26-2016, 05:54 PM   #13
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sounds like a switched neutral to me. i just dealt with one this weekend at my parents house. I dont do residential so this type of ****ery had my head spinning. with the switch on i got my normal 110, with the switch off i got 56V.

it wasnt a 3-way though, but im sure they switched the neutral somewhere just like in my case

did you try testing Hot to ground, and Neutral to ground?
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Old 07-26-2016, 06:00 PM   #14
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ground the hot when the switches are off. If no spark it's induced voltage. if it sparks and the breaker trips, you have a problem. Most likely induced if the 3 wire is particularly long.
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Old 07-26-2016, 11:12 PM   #15
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Are you sure it's not an illuminated switch? The open circuit voltage of 25 to 50 volts is on par for an illuminated switch. Many dimmers are without much labeling, lutron diva for example.
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Old 07-28-2016, 12:26 AM   #16
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sounds like a switched neutral to me. i just dealt with one this weekend at my parents house. I dont do residential so this type of ****ery had my head spinning. with the switch on i got my normal 110, with the switch off i got 56V.

it wasnt a 3-way though, but im sure they switched the neutral somewhere just like in my case

did you try testing Hot to ground, and Neutral to ground?
It might be a switched neutral. That hadn't occurred to me. I forgot people do that crap. I assumed the 2 loose wires in the box were my hot and neutral. Silly me. But I rang out the wire coming up from the dimmer and it was the switch leg/common of the 3-wire. So take that for what it's worth. Since nothing in the chandelier box was anything other than older BX-black, I don't know if the hot wire was tied through and the neutral was broken by the switching. Sorta makes sense when you think about it..

The switches were new, installed by me, so I know they're not illuminated.

Thanks folks, I should've come on here and asked this question before I went and finished the job!
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