Submitted by Unlikely_Play t3_11edc1l in DIY

As the title says, want to add a GFCI outside. Here's the current situation. House has an outdoor-rated junction box that's covered. I removed the covering and inside is a single 12x3 wire setup. All the wires (black, red, and white) are capped off, the ground is secured. No other wires are in the box indicating to me it is an end-of-the-line cable. The black wire is hot. The red wire becomes hot once a switch near the front door is turned on (in a panel that controls our entryway lighting). Both red and black are on the same 20amp breaker switch.

My question is can I change the current junction box for a two gang and install two outdoor GFCI outlets by connecting the red to one, the black to the other, and pigtailing the white to each one (while not violating code)? That way one outlet is always on and the other can be controlled by a switch.



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silverbullet52 t1_jadvw6x wrote

Just a thought...

Have you measured red to black? If the answer is 240, the situation may be a bit different than you think.


MyMomSaysIAmCool t1_jadxek6 wrote

OP said that they're both on the same breaker, so they should be safe. But your point is well taken.


WackTheHorld t1_jaec60z wrote

If they are 240v black to red, that's just fine as those wires will be on seperate receptacles. Using a two pole breaker and a shared neutral is a normal way of supplying two circuits (when and where and how depends on your local code).


arwans_ire t1_jaf0mvs wrote

I understand these words just not in the order they're used.


DJ_Spark_Shot t1_jaelwpk wrote

The red is switched and the black isn't. It's a light and utility circuit.


inna_hey t1_jadkwnb wrote

Sounds fine probably but you didn't mention a ground wire. Buy an outlet tester and ensure that ground is connected after installation.

>Here's the current situation.



craigeryjohn t1_jae6kbr wrote

OP said the ground is secured. Also FYI you don't actually need a ground wire for a gfci to function.


inna_hey t1_jae8tv2 wrote

Sure but it's still code & best practice to ground things


craigeryjohn t1_jae92gy wrote

Of course. Just letting everyone know that they aren't strictly needed in order to still protect yourself with a gfci.


ChefRoquefort t1_jaefqjb wrote

Unless you have an old house without ground wires and want a 3 prong plug.


Adj_Noun_1234 t1_jaf502s wrote

You don't NEED one, until you need it to be a ground fault circuit interrupter and it doesn't go to ground.


DJ_Spark_Shot t1_jaep49d wrote

Neutral wires connect to ground, anyhow. Being an outdoor box, it can be grounded on a rod rather than on the panel, saving the run of wire.


mechanismen t1_jaeyu7x wrote

Well yes, at the breaker panel. They serve different purposes until then though.


olala_tse t1_jade3z2 wrote

I think you can, and I would do it the way you describe it.


zolstarym t1_jaep5v7 wrote

I would recommend a gfci breaker rather than gfci outlets. That way the whole line is protected. Make sure both the red and black go to the same breaker.


WealthyMarmot t1_jadpl4u wrote

Your plan sounds fine to me. Someone really made your life easy by running that wire. Make sure the box itself is weather-resistant and grounded, and get the deepest one you can find because GFCIs are chonky.

Technically, your local jurisdiction probably requires permits to install new receptacles. Practically speaking, this is very low-risk. But keep that in mind.

edit: lol in the last two days I've probably installed 40 outlets/switches, including figuring out how to AFCI a weird old MWBC and deal with a busted Carter 3-way, but apparently DIY doesn't think I know what I'm doing


AccomplishedEnergy24 t1_jaepn1h wrote

You actually can't safely share a neutral between two different GFCI's with different hots, and run them to separate breakers - the neutral here will carry the difference between the two hots (and even if that was safe, it would trip the GFCI). The proper way to do it is a dual pole GFCI breaker.

This is the only safe way to get 2 15/20 amp GFCI protected circuits out of this situation. This is a standard MWBC application.

If you share a breaker, there is no point to using multiple GFCI's, may as well use one and run the other downstream, and ignore the extra hot.


WealthyMarmot t1_jaeqi3w wrote

They're not separate breakers. If my understanding is correct, it's just a single-pole, but someone ran a 12/3 from a switch to outside so that there's an optional switched hot in case someone wants to install a switched outlet (like OP does). The hots are on the same phase, unlike a MWBC.

Two GFCIs should work totally fine here. The neutral at each outlet is clean.


AccomplishedEnergy24 t1_jaerdxk wrote

Yes, if he runs them to the same breaker, it would be fine. But also pointless to GFCI both of them in that case. You can still switch the outlet with a single GFCI and GFCI protect both outlets if you want.


WealthyMarmot t1_jaermui wrote

If he wants to switch one and not the other, he needs to GFCI both. The best way would be a GFCI breaker but I don't usually recommend homeowners open their panels.


AccomplishedEnergy24 t1_jaewucc wrote


single pole GFCI breaker is not materially different than switching the load side of a single GFCI since he has a shared neutral and single shared breaker.

If it was a double pole GFCI and two circuits it would be different.

But in this single pole config, the circuit can't tell whether you have a GFCI breaker and switch the load downstream, or use a regular breaker + GFCI outlet and switch the load downstream of that.

It's the same exact circuit. You've just separated "thing providing overcurrent protection" from "thing detecting ground fault" instead of putting them in a single thing.

IE a GFCI breaker is the same as if you used a regular breaker and ran it all to a GFCI outlet next to the panel, and then ran everything downstream of that including the switch.

Switching in any of these cases (GFCI breaker, single GFCI + load switched beyond that, shared neutral and two GFCI's, etc) will likely cause nuisance trips, though the two former will probably be way worse than the latter.


Yowomboo t1_jaezj0d wrote

OP doesn't appear to want to run any new wire. Switching after the GFCI would require new wire. Swapping in a breaker solves this problem. However not being an electrician I don't know if swapping in a GFCI breaker could cause any other issues.

Given that OP is asking such a question I definitely wouldn't recommend they swap a breaker. They should 100% contact an electrician.

Edit: Just realized what you were getting at. Assuming OP could find an outlet that comes before the switch/outlet combo he could 100% swap that with a GFCI outlet. Again given the way this question is being asked with no additional information OP should call an electrician.


AccomplishedEnergy24 t1_jaep52l wrote

If you share a breaker (IE double tap a single breaker, rather than a single tandem breaker), there is no point in the extra GFCI. You gain nothing but work. You should ignore the extra hot in that case. You don't need it to switch the outlet.

If you want two 20 amp circuits out of this, it's a multi-wire branch circuit.

You can't share a neutral between two separately protected GFCI's if you use standard GFCI outlets (IE you can't run each hot + shared neutral to two different circuits with single-outlet GFCI's).

You can do it with a dual pole GFCI breaker instead. goes into detail about this.

Dual pole GFCI breakers can be expensive - like 120 bucks.


HyrulesRonin t1_jaefont wrote

So if both the red and black are on the same breaker then putting the red on a second GFI isn't going to really help you unless you want that plug controlled by the switch. If you just want two GFI protected plugs outside your easiest route would be to put the black and white on the line side of a GFI and a normal plug coming off of the load side. You'll save the money for the second GFI and both plugs will still be protected.


Jimid41 t1_jaf1obz wrote

> unless you want that plug controlled by the switch.

Which is what OP said in their post.


DJ_Spark_Shot t1_jaenucx wrote

The switch will trip the GFI if connected. Outdoor should already have a GFI on the un-switched circuit. You can't run 2gfi on the same circuit, so be sure there isn't another outlet on that circuit. They can get pretty weird, particularly on 50's-70's construction.

My deck outlet is run through the GFI in the master bath, the half bath is run through the basement/ sump gfi and the kitchen isn't protected so we're having to get a gfi panel breaker during the upcoming remodel.