GFCI wiring question

JimMorrissey · Dec 17, 2006

I've got a four wire cable coming into my new 100 amp sub-panel with a seperate ground bar I installed. I have connected one of the hot lines to a cellar circuit of recepticles (basement has the possibility of flooding if sump-pump fails). My question is, can I connect the shared common neutral wire for both hots (off the 4 wire cable) to the GFCI neutral connection and not cause problems for the other hot circuit that provides lights and convenience outlets on another floor?

Thanks for any help.

Inspector507 · Dec 17, 2006

If I understand your question correctly, no, it will not work.
I think you're referring to a 3-wire cable w/ground, using 2 hots and a common neutral. If that's the case, the GFCI will trip out.

JimMorrissey · Dec 17, 2006

Yes, you're correct it's 3 wire with two hots going to seperate circuit runs...sorry about that. I'm glad I asked before I cut anything in the panel.

Much appreciated.

JoeL4330 · Dec 17, 2006

Hmmmm...I am under the impression that you can, indeed, use a gfci outlet (rpt outlet) on just one leg ...i.e., from one hot to center neutral/white and that outlet and beyond (now, using 2-wire + grnd to subsequent outlets) will be gfci protected ... I could be wrong, of course ...easy to try and see if it trips, but don't see why the outlet would trip ... and, if it doesn't trip, invest in an inexpensive plug-in tester that can test/trip the gfci outlet (and, any outlets further along, wired as directed) ...

things might be different with a gfci breaker in the box, trying to share a common neutral with a non-gfci circuit ...

Inspector507 · Dec 17, 2006

JoeL4330 said:
Hmmmm...I am under the impression that you can, indeed, use a gfci outlet (rpt outlet) on just one leg ...i.e., from one hot to center neutral/white and that outlet and beyond (now, using 2-wire + grnd to subsequent outlets) will be gfci protected ... I could be wrong, of course ...easy to try and see if it trips, but don't see why the outlet would trip ... and, if it doesn't trip, invest in an inexpensive plug-in tester that can test/trip the gfci outlet (and, any outlets further along, wired as directed) ...

things might be different with a gfci breaker in the box, trying to share a common neutral with a non-gfci circuit ...

You're right, the GFCI receptacle will work fine. And if connected properly, it will protect the ones down stream. I kinda thought his question was about a GFCI breaker.

hockeypuck · Dec 17, 2006

I would put a single receptacle (not a duplex) in for the sump pump and leave that on one of the multiwire circuits. Then take the other leg of that circuit and put a GFCI on the first receptacle and hook the remaining cellar receptacles onto the load side of the GFCI. Mark the single receptacle cover for the pump as "not GFI proctected" . IMHO

puck

JimMorrissey · Dec 17, 2006

It is a breaker indeed. Just for kicks I tried it on an arc-fault breaker and it instantly tripped.

This is a small problem because I'm supposed to have an arc-fault in the bedroom, but the main bedroom leg down was run with 3 wire (two of which are used). Can anybody think of a way around this? Are there any options?

Dusty · Dec 17, 2006

Unless you just built this bedroom, I believe that you are exempt from the arc fault breaker requirement. If I remember correctly, Inspector 507 said that in one post a while ago. It is only for new construction, and the code doesn't require it to be retrofitted, as they do with GFI breakers in garages and outdoor recepticles. He is the final word when it comes to the Code, so please don't take what I am saying here as gospel, but check it out with your local building officials. Here is a "fact sheet" from the CPSC.
Dusty

JoeL4330 · Dec 18, 2006

JimMorrissey said:
It is a breaker indeed. Just for kicks I tried it on an arc-fault breaker and it instantly tripped.

This is a small problem because I'm supposed to have an arc-fault in the bedroom, but the main bedroom leg down was run with 3 wire (two of which are used). Can anybody think of a way around this? Are there any options?

I am confused, now ...3-wire would normally mean 3 insulated conductors, red (hot), black (hot) and white-neutral, along with a bare copper ground wire. If only 2 wires (plus the grnd) are used, then either: they red and black, which would gives you 220v across the two "legs"; or, the white-neutral and one of the two hot legs (red or black, not both). If it is the latter, which I infer, then the wire installer ran "3-wire" thinking to split the load and give you two different 110v circuits (on a long run, saved a little money in wire) and, then, when came time to hookup, the AFCI breaker requirement meant that only one leg, not both could be used...hence "only two of which are used." The unused (red or black) would not be connected to any breaker, and stowed safely in the breaker box with end capped with wire nut, ...maybe then taped... I would think.

I am not sure what all this has to do with the basement...

heehaw · Dec 18, 2006

why not use a 220V GFCI breaker and have the whole cable and everything connected to it protected? i know most folks know how those things work, but just in case, its kinda like a water line: it looks at how much water(current) goes out and how much water(current) comes back, and if theres a difference, it shuts off. i have a couple circuits that use the GF recept: and some that use GF breakers: i have never had to change a breaker, but have changed the recepts several times over the past 10-15 years. and i do test all of them yearly.
heehaw