A GFI will detect any "neutral short" downstream of the GFI. So if you had a GFI breaker in the breaker box, then a "neutral short" 2 feet away on that circuit would be detected. The neutral wire in that circuit goes directly to the GFI, not to the neutral bar.
Most GFCIs will test for the grounded neutral condition. Read this by Sam Goldwasser:
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I've seen that grounded neutral problem a lot. The last time was in a garage where someone had put in a new outlet they wired the incoming white wire to the box. Unfortunately they also ran the feed to the garage in BX that ran on the floor under the entry door. Salt corroded this BX to the point that the armor shield and the neutral opened up. When their 16 year old son flipped on the light during a rainstorm he got a hell of a shock.
While I certainly agree that you should not intentionally connect neutral to ground anywhere but at the service panel.
To keep it simple, assume we're talking about a GFI breaker servicing just one receptical:
If by "neutral short" you mean making a connection between the neutral lead screw on the GFI and the ground lead it's location, with no current flowing in the hot lead from that GFI and no currents imposed on the neutral or ground through paths to/from other things.
Under those conditions the neutral current and the hot current from the GFI are both zero, and zero equals zero. So, there should be no current imbalance for the GFI to detect and trip from.
If you put a load on that receptical, then I'd expect the GFI to trip because the shared part of the return current on the ground lead would not be seen by the GFI, so an inbalance would be sensed.
Yes read the URL I posted above just above the 3rd illustration under: Neutral to Ground fault detection. I knew GFCIs could do this but wasn't clear how. Now I also know. Rlchard
You learn something everyday. I originally just meant that a Neutral to Ground fault would be detected when you apply a load, but as stated some GFCIs detect them as soon as power is applied.
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