GFCI Operation

[eelectric]

For a GFCI receptacle, under which of the below will it trip:

A.) Hot and neutral are shorted
B.) Neutral and ground are shorted

My understanding of GFCI's, is that it would trip under (B) since some of the current would be going back on the ground and not all back on the neutral. I think under condition (A) it still see a total current of zero and not trip, but the upstream breaker would trip.

 

[DRWeig]

You are correct.

However, if hot and neutral are shorted, the circuit breaker upstream will trip...

Good on ya,

Goober Dave

 

[MAGTiger]

Doesn't that depend on there being some small amount of load on the neutral circuit so that it has at least a small votlage rise with respect to ground so that current will flow from neutral to ground? If there is no current in the neutral to begin with. then the neutral will be at ground voltage (because they are tied together in the panel). If they are at the same voltage there won;t be any current.

Neil

 

[itsmoked]

Yes MAGTiger. The load would need to be energized and drawing some current.

Also it should be pointed out that if the neutral and the ground are shorted at the GFI or anywhere else before it the GFI would not notice at all.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[resqcapt19]

Neil,
In the past that was correct, but most of the newer GFCI devices have an additional circuit to detect a neutral ground fault even when there is no current flow on the load side of the GFCI.