The Neutral and Ground are together at one place in the circuit breaker
If, for example, you had a neutral short to ground within 2 or 3 feet
of the breaker box, would a GFI be able to detect the short?
In other words, within a few feet, is there any practical difference
betweern Neutral and Ground?
Is there a minimum distance where it begins to matter?
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.
Would you please explain why that is Wayne?
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.
Am I missing something here?
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.
Most GFCIs will test for the grounded neutral condition. Read this by
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.
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