Voltage on neutral

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SheppardJ

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New construction home and customer complained about their LED recessed cans in living room glowing at night. They do not emit enough light during the day to notice but when it completely dark there is a small amount of light emitted. Upon visiting the site my tech discovered 12v on the neutral wire. Anyone else experienced this in new construction, or suggestions how to remove the neutral voltage?
 
I had this happen to me. technical support they recommended to me to put it in one I inconsistent bulb in each switched circuit . And this would care of the problem. It did. Voltage on the neutral is supposed to be there sensing what each other switch is doing. At least that’s what technical support indicated to me.

Jim


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Sorry. One more thing. That was with Lutron dimmers.


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jksmith82 said:
. . . they recommended to me to put it in one I inconsistent bulb in each switched circuit .
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I would think an incandescent bulb would be more inconsistent. :D

Voltage on the neutral is supposed to be there sensing what each other switch is doing.
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Voltage measured between the neutral and EGC should be close to zero all all times.
 
Hi Larry, I agree 100% I was extremely baffled as well but I did with their technical support said and it corrected the problem. The Dimming system I was talking about had dimmers in 4 different locations. Their technical support had told me the small amount of voltage was so dimmers could talk to each other so to speak. I also looked on line at their technical support site and it said to do the same thing there as well. I unfortunately cannot remember the style of lutron system it was. It was about a year ago.

Jim


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You have two separate issues here:

The LEDs are glowing because of a very slight voltage across the supply terminals causing a small current to flow. This could be caused by leakage through the dimmer, capacitive coupling, etc. It doesn't take much current to barely light up an LED. The incandescent bulb is acting as a bleeder resistor, making the small voltage go away and making the LEDs go dark.

The separate issue is the voltage on the neutral. The neutral should be a solid metallic connection back to the service, where it should be bonded to the grounding and EGC system. There should be only a slight voltage on the neutral, especially on a branch circuit from the main panel.

My first question is 'exactly how was this voltage measured', and depending on the answer I would be looking for real problems such as an open EGC.

-Jon
 
This is a common issue especially when the lights are on a dimmer. Some dimmers (Lutron) are adjustable so you may be able to deal with it that way
 
Let's get deeper in to this. First off, 12 volts on the neutral wire relative to what? As I tell my students, 12 volts means nothing. What is the voltage of earth? Earth to what? The moon, a kid's finger just after he rubs his feet on the carpet...? Assuming the OP meant to ground, then what does the hot read to ground? If you read 12 volts to ground on the neutral there is only one scenario, electrically. There is a resistance between the grounded wire and the grounding wire somewhere and voltage is being applied to either the neutral or the ground. So, are the dimmers creating this on the entire house system or just in the circuit for the lights? If the first is true I think it is time to get new dimmers. I think that is the reason for the additional wire at switch boxes today.
 
SheppardJ said:
The 12v was read from neutral to ground. There are dimmers in this house.
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So what else have you found? This may be simplistic, but maybe try it. Remember electricity flow has to start at the red or the black wire at the meter and "get back" to the meter either on the other color or the white. That is the ONLY way the light will glow. Find that path. Start at the meter. Think of your self as one electron. Start running along the wire and find a path that goes through the light and back to the meter without being blocked. For example, and it might have some bearing. A lighted switch or a 120 volt occupancy sensor switch like a WS250 Wattstopper actually use the ground for the very small amount of wattage needed. This is changing and that is why we are now required to bring a neutral to switch locations. So the electron flows from black along the wire, through the neon lamp in the switch, to the ground, back to the service panel along the green and then to the white wire at the bonding point and back to the meter.
 
Continuing on what strathead was saying:

Imagine if the ground is not connected somewhere, or has a poor connection. Control current that normally flows through the dimmer to the ground wire would raise the voltage of the ground wire. This might also cause the dimmer to not function quite correctly when off.

When the dimmer is _on_ current could then flow through the load, and the dimmer would seem to function.

You might try running a wire to a known good ground on a separate circuit, and using that known good ground as a reference to measure the voltages again. Then you would know if the neutral on the questionable circuit is at 12V relative to a reliable ground, or if the _ground_ on the questionable circuit is at 12V. It might very well be the case that the neutral is perfect, but that your ground reference was poor.

-Jon
 
181004-1002 EDT

Neither ground or neutral have been defined in this thread.

Assume use of "ground" really meant EGC, then where on the EGC was the measurement made? If you go to the main panel and measure the voltage difference between the neutral and EGC bus bars, then is this value in the low millivolt range? Should be. Mine reads 0.5 millivolts. Some of this may be induced into the 1 turn loop of the test leads.

Run a test lead (an extension cord) from the main panel EGC to the location where "ground" (presumably the EGC) was being used as one point of the 12 V measurement. What is the measurement? I read about 0.07 V at about 50 ft from my main panel to my work bench with a Fluke 27. At my bench location are some noise filters to the EGC.

How could one get a 12 V drop on a neutral of 50 ft of #12 copper. Assume 1.6 ohms/1000 ft. 12 V across 0.08 ohms = 150 A. That current level does not exist. At 20 A the drop would be 20*0.08 = 1.6 V. Assumptions being that for short distances at 60 Hz that inductance can be neglected.

SheppardJ needs to provide more details on the circuit and measurement points.

.
 
When are we going to learn that you can't rely on readings like this using a digital meter that normally has a high impedance input? I really suspect this is a "ghost" voltage and means nothing. If you want to confirm put a load across your meter probes. I carry a 25W light bulb in a rubber pigtail socket. Comes in handy for lots of other things too.

And yes, capacitive leakage between conductors on a switch leg (no dimmers involved) can provide enough voltage to dimly light LEDs with the switches in the off position. Since this is a 3-way setup even more I suspect there is enough wire to cause this.

Your remedy is to either add an incandescent load besides the LEDs (here's where your 25W test lamp comes in handy again) or try other LEDs.

-Hal
 
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