gfci and shared neutral

The gfci should work on the end of a shared neutral circuit I believe??? Or am I full of it? What trips them when used on these circuits?

 

A GCFI outlet will trip all the time on a shared neutral. A GCFI will look for the difference between the hot and neutral wire (current). They should be equal if everything works ok. If something happens then more current will flow through the hot wire then the neutral, and the GCFI will trip. The only way to make this work I guess is to use a double pole GCFI breaker.

 

The load side of a GFCI cannot be connected to a neutral that is shared by two different hot wires downstream. Otherwise, the current will mismatch as soon as any current is taken from the hot wire other than the one connected to the load side of the GFCI. This will trip the GFCI every time.

In practical terms, this means that you must do one of three things to use a GFCI on a shared neutral circuit: (1) Use a 240/120 GFCI breaker rather than a GFCI receptacle; the GFCI breaker has the ability to compare the current in all three wires -- both hots and the neutral. (2) Split the neutral before connecting to the GFCI. E.g., convert the 12/3 to two 12/2 cables before applying GFCI. In this case, the receptacles downstream from the GFCI are all on the same hot and the load-side neutral is not shared. (3) Don't use the load side of the GFCI receptacle for downstream protection; this means using a separate GFCI receptacle in every outlet that requires protection.

If by "end of a shared neutral circuit" you mean that you won't be using the load terminals of the GFCI, then yes, that'll work (condition (3) above).

 

Thanks you guys,,, thats what I thought, just wanted to make sure I wasnt missing something simple.