Outdoor outlets and GFCI

[Percival P. Cassidy]

I am planning to put two adjacent outdoor duplex outlets on an Edison circuit (shared neutral). Obviously they should be GFCI protected, but I am wondering which is the best way to do this, both from the NEC point of view and from a convenience point of view.

The three options I see are:

1. Two separate GFCI outlets -- the cheapest solution, AFAICS.

1. Two separate GFCI breakers.

2. Ganged GFCI breakers (separate breakers with a handle tie -- if available for Cutler-Hammer CH)

1. 2-pole GFCI breaker -- probably the most expensive solution.

Have I missed any? Which would be best?

Perce

[Goedjn]

I didn't think you could make a GFCI outlet work on an edison circut.

[Percival P. Cassidy]

Doh! Of course you are correct. What was I thinking!?

OK, scrub #1. What about the others?

Perce

[Toller]

Interesting! You dropped the only one that made sense. Assuming an Edison circuit is the same as a multiwire circuit, the outlets don't know what they are on; the neutral current is only reduced when the two branchs come together; so anything on the common neutral will not work, but anything on the split neutrals will work fine.

[Jeff Wisnia]

I can't think of any technical reason why a GFCI "outlet" would not work on a shared neutral circuit.

The detection of a ground fault is done by noting imbalanced currents in the hot and neutral leads of whatever's plugged into the receptical, and that takes place entirely withing the receptical. The sensing of a neutral to ground fault is similarly done within the receptical.

If I'm wrong about that I'd appreciate learning why.

I'd try it and see.... I prefer using GFCI outlets because when they trip it's pretty certain there IS a true ground fault in whatever is plugged into them, and not just a little too much condensation inside some junction box or bathroom exhaust fan.

Jeff

[Tom The Great]

IMHO:

Unless they sell a double pole GFCI breaker(for the shared neutral) I think you only option is #1. P.S. I think this type of breark (#4) is expensive if it exists.

The shared neutral(guessing you are doing something like 14/3 or 12/3 circuit) means that #2, #3 aren't feasible.

You can splt the neutral and feed seperate GFCI receptacles, and each GFCI receptacle.

Now this is just guessing, since I can't actually see what you are doing.

later,

tom

[Mark Lloyd]

You can. Just connect them AFTER you separate the neutrals.

[Mark Lloyd]

Some people don't seem to recognize the difference between a shared neutral on the LOAD side of the GFCIs (won't work) and a shared neutral on the LINE side of the GFCIs (no problem).

[Mark Lloyd]

Both #2 and #3 sound impossible (with a shared neutral). There would be no way to connect the neutral properly. You would be unable to use more than 1 outlet at a time.

I think #1 is best.

[Nate Nagel]

Ayup, with a shared neutral, there's no way to use a GFCI breaker because the GFCI works by comparing hot and neutral current. You need GFCI outlets installed after the point at which the two circuits diverge.

nate

[terry]

Maybe one way to discuss this is;

1) Suppose that you have an 'edison' (split) outlet. Assume for the moment it is, say, inside the house.

2) Beyond, i.e. further downstream of that, and for use outside, you install two duplex GFCI outlets. One of them uses one of the 120 v legs and the neutral. The other uses the other leg and the neutral. The neutral splitting 'before' going separately to each GFCI. The neutral cannot 'go through' one GFCI to reach the other.

3) Anything plugged into either of the GFCI which causes an unbalance of the neutral and live wire currents flowing to/from that outlet will cause it to trip and protect. The other GFCI will not trip.

4) Even if one or both of the GFCI operate, the edison outlet will still be fully live on both parts of its split personality. In fact after installing the two GFCI you could eliminate it! Or not install it all in the first place?

Assuming the edison arrangement and two GFCI outlets are needed because of an expected larger load than the 15 amps that can be drawn from a single duplex outlet (GFCI or otherwise)? If not one (non edison) GFCI outlet could be installed and a 'regular' outlet downstreamed from that! Both would be protected by the single GFCI.

BTW I came across an older GFCI of the type that does not allow another outlet to be downstream of it. So installed it in a metal box at the end of an older but substantial extension cord. This provides a GFCI protected circuit no matter where plugged in; for example can be plugged inside the house into a regular non GFCI outlet and run out through a window to work on something outside.