Hate asking this but I will. GFCI issue

[green.bubbly]

Building my house and would like to start working at night inside of it. On my main panel, I have a few light circuits on one side of the panel.

Want I wanted to do was hook up a male plug to one side of the panel so I could use a few of the light circuits by turning on a couple of breakers for the lights. When it was time to leave, I would just unplug the plug to the panel.


The plug would plug into an extension cord running out to my temp pole. So far so good. Problem is that when I plug the plug into the extension cord, it trips the gfci receptacle on my temp pole.

To trouble shoot, I disconnected the hot wire feeding my panel from the plug. All I have is the neutral and the ground from the plug attached to the same bus and it still trips the gfci.

The polarity of the extension cord is correct and the cord works fine if I plug anything else into it. 120 volts between the ground prong and the wide terminal.
Any thoughts other than I should not be running power to my panel.


***edit** I left only the neutral connected to the bus bar and it still trips the GFCI. All breakers are off. ???

 

[Worsedog]

Start with the fact the large prong is the neutral............troubleshoot from there.

 

[green.bubbly]

With the panel not plugged in, I do read 2.2 volts between the neutral of the extension cord and the neutral bus of the panel. Seems there is a difference of potential for some reason???

Could it be a poor ground at the temp pole?

 

[pattenp]

I think I understand what you're doing and if so the problem is the neutral and ground are bonded in the main panel which is causing an imbalance in the neutral causing the gfci back at the temp pole to trip.

 

[green.bubbly]

Yes the ground and neutral are bonded at in my main panel. To hopefully clarify what I was wanting to do wa to run and extension cord from my temp pole to my main panel. Connect the hot from the cord to one leg of my panel and the connect the neutral and ground from the cord to the bonded neutral/ground bus in the panel.

To simplify the issue I see, basically when just the neutral wire from my main panel bus is connected to the neutral of the extension cord, the gfci trips on the temp pole.

I tend to agree that it has to do with the bonding in my panel since there is nothing else connected to the panel.

Would it be safe to temporary disconnect the ground from the main panel to the earth ground?

 

[pattenp]

Think of what you're doing is you are using your main panel as a sub panel off of the temp pole gfci outlet. If the main was wired as a sub without the neutrals and grounds bonded you wouldn't be having this problem. Disconnecting the ground from earth at the main will not solve the problem, you need to isolate the neutrals from the grounds after the gfci.

 

[Gary S]

The polarity of the extension cord is correct and the cord works fine if I plug anything else into it. 120 volts between the ground prong and the wide terminal.

You have the polarity backwards. The small prong is hot!

Better get an electrician to help before you get hurt.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/hsehld.html#c2

 

[pattenp]

Good catch Gary, I didn't notice that. That will make a big difference.

Originally Posted by green.bubbly

The polarity of the extension cord is correct and the cord works fine if I plug anything else into it. 120 volts between the ground prong and the wide terminal.

You have the polarity backwards. The small prong is hot!

Better get an electrician to help before you get hurt.

 

[ddawg16]

Basically, you want to backfeed your load center.....I was doing that with mine a few months ago....except I just ran a 10/2 SO cord from a 50A breaker in my old panel to one of the new breakers in the new panel.

Did you verify your polarity like Gary said?

You might consider just running an SO cord from your temp panel to one of the breakers in your new panel (back feed it). And make sure you have the polarity right.

 

[green.bubbly]

You have the polarity backwards. The small prong is hot!

Better get an electrician to help before you get hurt.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/hsehld.html#c2

No no, I had it right in my head but typed it wrong. Large spade with bright screw is neutral and the small spade with the dark screw is hot.

I think faster than I type and I don't think very fast.

Thanks for the catch though.

 

[Charles (in GA)]

The polarity of the extension cord is correct and the cord works fine if I plug anything else into it. 120 volts between the ground prong and the wide terminal.

You should show no voltage between the wide prong and ground. The wide prong is the white or neutral wire, there should not be anything showing between neutral and ground.

In your panel do you have voltage between neutral and ground?

It sounds like the hot and neutral are reversed.

Charles

 

[green.bubbly]

You should show no voltage between the wide prong and ground. The wide prong is the white or neutral wire, there should not be anything showing between neutral and ground.

In your panel do you have voltage between neutral and ground?

It sounds like the hot and neutral are reversed.

Charles

With the extension cord not connected to the panel, there is zero between neutral and ground on the panel being that it is bonded and no power being fed into it.

Now I did measure between the neutral bus in my panel and the neutral on my extension cord and read 2.2 volts.

On my cord, I have zero between the ground lug and the wide spade and 120 between the ground and the small spade with indicates polarity is correct. I have a polarity checker hiding somewhere. I will test it with that just to confirm.

 

[pattenp]

If you are using a digital volt meter I believe you are getting what's known as a ghost reading. It's not a valid reading.

 

[Sunstealer73]

I think you just need to temporarily remove the neutral to ground bonding on your panel. When it is bonded as a sub panel to your temp hookup, you could have current flowing on the ground versus the neutral which would cause the GFCI to trip. Just reminder to put it back when you get your permanent hookup.

 

[Fisheye]

Green.Bubbly,
First; I want to say hello to all. Im new to garagejournal, but not to residential electrical construction. Im a 2nd gen electrician; however, I can admit this field still challenges me.
From what I gathered you want to heat up your new homes Branch Circuit Panel by using your temporary service panels GFI receptacle, a drop cord, and a male cord end that is connected to your Home Branch panels busbar via another drop cord . I believe pattenp has the answer. First; all neutral and ground wires should be terminated separately all the way back to the service meter panel(temp) were the Neut and Ground is bonded together ITS A National Electrical Code rule. If these are separated then Ide say all that wire plus the breaker plus more wire is causing the trip due to stray capacitance. What goes out must come back, just in reverse polarity. These new GFRs are rather sensitive. A difference of 5-30 milliamps will cause a trip. This is why GFI breakers should not be used on circuits that are a long distance from the breaker panel. Stray capacitance(amps consumed by the long copper wire) causes nuisance tripping. Good tool to have is a plug-in tester with GFR test from your local big box store. This tester will indicate any miswiring. Also, any miswire will be detected by the GFR
Ways to correct: Eliminate the GFR and run a chunk of Romex, 12gauge is good for 20 amps(120volt x 20amps=2400watts), from your temp service panel, hopefully you have an extra breaker space in that temp panel, to your new homes branch circuit panel. Even safer yet turn off temp breaker, pull out GFR, wirenut cord to those wires, turn breaker back on ( avoids workin in hot panel). Then install GFR in your already installed garage outlet box. Turn on that circuits breaker and plug in your lights. You will still have personal shock protection! Though; I think you stated you were going to turn on some existing lighting circuit breakers? Ok, turn on lighting circuits when you arrive, when you leave turn off lighting circuits and turn on houses temp GFR when you leave. Tell construction workers to now use that outlet for temp power.

http://en.wikipedia.org/wiki/Residual-current_device

Electricity takes the path of least resistance, you should to!

 

[green.bubbly]

Green.Bubbly,
First; I want to say hello to all. Im new to garagejournal, but not to residential electrical construction. Im a 2nd gen electrician; however, I can admit this field still challenges me.

That was a hell of a first post!

Welcome to GJ.

Separating the grounds and the neutrals in my panel could be done but it would not be worth the trouble. I can continue using drop lights and the one Kitchen circuit I have connected to the extension cord. It would have been convenient to have a few live circuits but I still need GFCI at my temp pole as I would still be running another extension cord from it for tools.