Help Trouble Shooting Current Between Ground and Neutral

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  #1  
Old 04-03-07, 07:21 PM
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Help Trouble Shooting Current Between Ground and Neutral

I need some help troubleshooting current between ground and neutral in my electrical panel.

The space in question is a condo remodel and all the wiring and panel is new. I was working on a circuit and the neutral wire touched the frame and small spark appeared. I took out my meter and I measured about 7 amps of power at about 1.5 volts.

I then tried to do some troubleshooting - not everything is installed so there are only a few loads to check and I was able to isolate the source of most of the current. I have a dimming panel that consists of 5 Lutron Grafik Eye units. 2 of the units are on one 20 AMP breaker and three of the units are on another 20 AMP breaker. The breakers sit below each other in the panel so they are on different legs of the feed. The load on each circuit is pretty balanced - i.e. when all lights are on about 17-18 amps is being drawn on each circuit. The troubleshooting I did was with all the lights on (i.e. full load on each Grafik Eye). The other load I used in my troubleshooting was a fan for the fireplace heater. This is connected to a different circuit. I tried various combinations of on/off among the loads and measured both the current and voltage between the neutral and the ground. To do this I attached one lead of the meter to the main panel bus bar and the other lead to the main panel ground (there are no sub panels in the system). I am using a Fluke 87 meter and take the voltage reading then reconfigure the leads in the meter to take the amperage reading.

Here is what I got:

Lutron Panel On/ Fan On 6.8 Amps 1.4 Volts
Lutron Pane On/ No Fan 7 Amps, 1.4 Volts
(if I turn off one of the two Lutron breakers off the voltage stays the same but the Amps drop by 1.2)
Lutron Panel OFF/Fan On .4 Amps 100mv - Effectively ZERO
Lutron Off/Fan OFF .2 Amps, 62 mv - Effectively ZERO

Thoughts and Suggestions are welcome.

Thanks,
David
 
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Old 04-03-07, 07:36 PM
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first, current on a neutral is normal. The only time you won;t have current on the neut is if everything is off or the circuits that are being used are perfectly balanced on a shared neut.

Now depending if this is a service panel or a sub of the service would make a difference about the voltage reading. If it is the service and the beutral is made up, you chould have 0 volts at the panl

If you have an open neutral, you should read 120 (or whatever voltage is at your service) to ground If the circuit is being used.

Now the one other thing; every dimmer package I have worked on required seperate neuts for each circuit and each circuit within the dimmer has it's own neut to the dimmer. Are you charing any neuts?

The other thing you are not very clear about is what neutral are you concerned with? An individual circuit neut; the main neut back to the service panel or the main neut back to the POCO. It makes a difference.
 
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Old 04-03-07, 08:07 PM
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Thanks for the reply - clarification of issues raised

Thanks for your response. After I posted this I was thinking about what I had done and realized that my current measurement between the ground bar and the neutral bar in the panel is probably not valid because the meter was in parallel with the circuit not in series.

Now to clarify your questions and provide some additional information.

What started this was when a neutral touched the frame and I saw a small spark in a circuit that was supposed to be off, (breaker energized but switch off). In this particular case the switch is a relay panel. When I saw this I believe I did make a correct amperage measurement putting the meter in series between the neutral and ground. I got similar values to those expressed above about 6 amps and 1.5 volts. What has occured to me is that what I was measuring was not a ground neutral issue but potentially some leakage in the relay controlling the circuit. Since the relay was supposed to be off and the ground was removed the only way there could be current would be iff the circuit was not completely closed. (I have effectively measured no voltage (1.5 volts) between the ground and neutral.

As for the Grafix Eye Dimmers - Each unit controls six loads or zones. Each unit has a ground lug, a hot lug for power to the unit, a neutral lug and 6 hot lugs for each of the loads. Each zones load goes to the hot lug. The neutral from each load is connected together with the neutral for the device. The hot feed from the panel goes to a hot lug on the dimmer. As I said before tow of these units are on one 20 Amp breaker and three on a another.

Agan the more I think about this - the more I think the issue I observed was incomplete closure of the line voltage side of a relay system. Does that sound reasonable?

Thanks again,
David
 
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Old 04-03-07, 08:30 PM
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several thoughts;

many pieces of equipement use current even when it is turned off (think; television). A grafik eye may very well have some circuitry that remains energized even of the device is "off" as long as the circuit to the device is on and the device connected.

also, there are often induce voltages in non-energized power lines due to the proximity of thme to an energized power line. This could result in seeing a small spark.

try taking the readings with that particular circuit breaker turned off but everything else the same.

also, do you have a good ground to the grafix eye?
 
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