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Should I have 120v on hot to neutral as well as hot to ground?

Should I have 120v on hot to neutral as well as hot to ground?

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  #1  
Old 02-07-15, 03:34 PM
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Question Should I have 120v on hot to neutral as well as hot to ground?

http://tinypic. com/r/e62hhg/8

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I know I should have 120v on the hot/neutral contacts, and zero on the neutral/ground contacts. I am pretty sure I shouldn't have 120v on the hot/ground unless I have a ground fault. If so, that would explain why my GFCI breaker trips with a load, right?

Everything works with a standard breaker, even with a load. I am also not sure why my GFCI doesn't trip, unless I try to turn on a light or operate a saw. I've reduced the circuit down to just a single outlet in my shed, which is also grounded to 2 ground rods I installed, 6ft apart.

Is there a specific test device that would make this possible to troubleshoot?
 
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Old 02-07-15, 03:45 PM
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Being able to measure voltage to ground as well as voltage to neutral is normal.

. You might have a neutral touching a ground.
 
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Old 02-07-15, 04:01 PM
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Neutral to ground is only connected together at the main breaker panel. It is kept separate from there, through the splice in the empty main lug, to the initial outlet in the garage.

Any test methods/tools besides a cheap volt meter to determine where things go wrong?

I appreciate any and all input, thanks.
 
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Old 02-07-15, 04:29 PM
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If the gfi is tripping you have current flowing on something besides the neutral. The ground is one path it can take.
 
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Old 02-07-15, 04:47 PM
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Your link does not work. Upload your picture to a hosting site like photobucket and post the link here.

A GFCI will trip if there is an imbalance between the hot and neutral wires. The theory is if there is an imbalance, current is leaking to ground. However, if something is miswired, that will also cause a GFCI to trip. The same would be true when a load is applied.

Ground rods do not provide a ground, they are a low impedance path for things like lightning strikes. If this is a new installation you should have a ground wire running with the other wires from the house.
 
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Old 02-07-15, 05:03 PM
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http://i473.photobucket.com/albums/r...%20diagram.jpg

This rudimentary diagram shows my situation much faster than using words. If anything looks off, please let me know. Thanks in advance.
 
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Old 02-07-15, 05:16 PM
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Your voltmeter measures potential difference between the wires you are testing. Your neutral should have 0V on it, and your hot should be +/-120V. Therefore, there is a difference of 120V between your hot and neutral, same with your ground/bond.
Is it yankee code to have ground rods at your shed? And is it code to have GFCI protection IN the shed? I'm not understanding why you can't have a standard receptacle and breaker in there.
Also, is it just the table saw that trips the GFCI breaker? Motor loads can nuisance trip GFCIs.
 
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Old 02-07-15, 05:20 PM
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In the drawing you show the neutral of the feeder to the sub-panel as being connected to the neutral bus in the service (main) panel. This neutral (the feeder neutral) MUST connect to the neutral connection of the GFCI circuit breaker.
 
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Old 02-07-15, 05:24 PM
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pretty sure I shouldn't have 120v on the hot/ground unless I have a ground fault. If so, that would explain why my GFCI breaker trips with a load, right
If you have (let's say) 119.5 volts measuring neutral to hot, and 119.5 measuring hot to ground, this means you have a good ground. Nothing wrong there.
Motors can cause GFCI to trip. The electricians can explain why better than me.
 
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Old 02-07-15, 05:54 PM
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Sounds like I have a good ground. Ok, to respond to your responses...

The GFCI breaker has two poles(30amp) and a white pigtail. I connected the hot wire to one of the screw terminals on the breaker, and the white pigtail to the bar inside the main panel that all the other neutrals go to. That neutral bar also has the neutral wire of the circuit. Then I have the ground wire of the circuit, going to the ground bar inside the main panel.

As far as the tripping of the GFCI goes, that's with flipping on the light switch, when I had it connected. Keep in mind everything works with the regular breaker installed instead. I had lights, a fan, and a grinder all working at the same time. The reason I am trying to get the GFCI working, is because the shed's circuit is going to be used for the pool I'm installing for this summer. Even though the pool pump and salt generator has GFCI built into the plugs, I don't want to risk electrocution. This is also why I was asking about a hot/ground with 120v.
 
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Old 02-07-15, 06:09 PM
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GFCI circuit breakers have BOTH hot and neutral terminals for the circuit. A two-pole GFCI circuit breaker would have THREE circuit terminals in addition to the neutral pigtail. The circuit neutral MUST be connected to the neutral of the GFCI or it will trip every time from an imbalance between the current going out and the current returning.

IF your particular GFCI circuit breaker does NOT have a neutral terminal then it is for 240 volt loads ONLY and cannot be used in your application.
 
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Old 02-07-15, 06:09 PM
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Your GFCI breaker should have the neutral for the shed circuit attached to it. Try that and see if it still nuisance trips.
 
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Old 02-07-15, 06:47 PM
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Agreed, the breaker is miswired.

What is this powering? General purpose receptacles are limited to 20 amps maximum under the NEC.
 
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Old 02-07-15, 08:12 PM
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Red face

Ok. You all have been really great and helpful. I think you all figured it out. Too late to test it tonight, but tomorrow morning I hope to post a message of success.

I wired the GFCI breaker wrong apparently. There are actually 3 screw terminals. The middle one has the white pigtail, and a faint white blotch above the screw. I naively assumed, because it was tightened all the way in, that it was somehow reserved for the pigtail and not to be used. Don't ask me where my logic was in that assumption. The pigtail doesn't actually emanate from the screw terminal, but from a hole below it. It seems obvious that moving the neutral from the neutral bus in the main panel, to the GFCI neutral breaker screw terminal, will fix the tripping.

Thanks for reminding me about the wire gauge amp limit. I don't actually plan to ever exceed 20amps, even with the pool running, but I will pick up a 20amp GFCI breaker sometime in the near future, just to be safe.
 
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