How should I handle the third wire when installing a GFI in my kitchen with 3 wires and a ground?
Asked by Etienne Claire 
3 months ago
Last Updated: September 2, 2024
I’m thinking about putting in a GFI in my kitchen. The wires already in place have 3 wires and a ground. I’m a bit confused about what to do with the third wire since the instructions don’t mention that scenario.
Looks like you’ve got a split receptacle where the top and bottom can be controlled independently. GFCIs can’t accommodate that. You’ll need to remove one or provide protection at the breaker or an earlier point in the circuit.
I often see these used to control a sink disposal. One plug remains energized, while the other is operated by a switch.
This is typically done in kitchens to avoid overloading, like having a kettle and toaster plugged into the same outlet equals more than 15 amps. That’s why the top and bottom are connected to separate 15 amp circuits.
Should a disposal have its own circuit above the counter, right?
You really hit the nail on the head, Doug. Great observation.
Pointed out that the word “usually” can be applied in various contexts.
I just noticed there isn’t a disposal plug above the counter.
Is a bit odd, but he’s the perfect example I could come up with. 🙂
Installing a GFCI breaker to replace the outlet switch
Did you switch the outlet on a counter next to a sink?
Yeah, sometimes they’re used for disposal…they have many different uses or separate breakers on top and bottom. Can’t really tell from the photo
Wouldn’t the plug for a garbage disposal have to be under the sink, the plug?
Was just using it as an example.
Piggybacking off the responses that have already been provided…
You can either have all your outlets connected to the switch (using the red wire and capping off the black wire)
OR
Have all your outlets always live (cap off the red wire and use the black wire).
Wait, how can you tell if it’s being powered by two circuits instead of just one?
Haha it’s actually on two circuits
Has the option to be set up in a few different ways. It can have one 110 circuit with one switched outlet, one 110 circuit with two switched outlets, two 110 circuits with one switched outlet, two 110 circuits with two switched outlets, or just two 110 circuits. And you can connect it to either one single pole breaker, two single pole breakers, or one double pole breaker.
Maybe you should consider telling Jim instead of me, since I wasn’t the one who made the statement without knowing the details.
Might be onto something, or maybe he’s not. Jim seems convinced that something has changed, but I still wonder how he can be so sure when we don’t have enough details.
I would guess that it’s probably not switched since it’s on the counter by the sink. Who would switch a plug on the counter, right? I’ve never seen that happen in my career.
If you take a closer look, Harold, you’ll see that the jumper is broken and two circuits are feeding into this outlet. The top circuit is different from the bottom one on the device. Just thought I’d share my two cents.
I didn’t mention anything about wanting a replacement. I simply wanted clarification from someone who claimed to know based on the available information and photos. It’s not really helpful to assert something definitively without being completely certain.
There are individuals here seeking guidance who may not be experienced in this area, so it’s risky to provide them with inaccurate information. Asking a few key questions could help us offer more reliable advice, but even then, without hands-on troubleshooting, we can’t be absolutely certain like you are.
If these individuals were experts or fully trusted in your responses, they wouldn’t be seeking assistance here, right?
Equipping them with accurate and realistic guidance is much more beneficial than offering speculative certainty.
This isn’t a switched outlet, as Doug mentioned, it’s actually a split receptacle. The disposal should have its own circuit. The new code requires a GFCI, but it appears to be wired with 12/2 instead of 14/3. Why do you want to switch to a GFCI? Essentially, you have two hot lines and a neutral, with each hot line connected to a separate breaker.
Hey , have you heard of a multi wire branch circuit? It’s actually a code requirement. I think the breaker either needs to be two breakers tied together or a double pole breaker, so they can be shut off at the same time.
Oh, by the way, , this method has been used for a long time. Shared neutrals were quite common.
You know, , MWBCs are still pretty popular. Almost every electric service in the US uses them.
Hey, ! How can you be sure it’s not a switched outlet? And who mentioned a disposal?
Yep, at the entrance. No longer coding on. In Lake County IL for branch circuits. I discovered several shared neutrals on my lighting circuits.
It’s odd that your county would eliminate MWBC’s but if you say so 🤷🏽♂️
It’s interesting that they can only be turned off together, but sure.
It looks like it’s positioned above a countertop, which is a bit odd for a switched outlet. I was also confused by the recommendation to use it for a disposal. Plugging a disposal into that spot would definitely be strange. And I think disposals are supposed to be on their own circuit.
I would need to ask more questions to get a better answer. I’ve seen a lot of things that didn’t make sense over the years, so it’s hard to definitively say whether something is or isn’t based solely on pictures. My question is, how can someone be so sure it’s not something based on the information provided? I may have an idea of what it could be, but experience has taught me that things aren’t always as they seem. So, for Fred to confidently state what it is with the information given is just not accurate.
That’s exactly what I was trying to say. Thanks for clearing that up!
In older homes, kitchen outlets were often wired as split receptacles. You can’t simply add to a split receptacle. I addressed two points. What makes you think it’s a switched outlet? Typically, a 14/3 wire is used for split receptacles, and that’s exactly what the wiring seems to be in this case. It could be switched, yes, but based on the wiring alone, it doesn’t appear that way.
Hey , what do you mean you can’t add to a split receptacle?
I can’t say for sure if it’s switched or not, and before forming an opinion, I’d need some questions answered. Even then, I won’t make any definitive statements like you did because I’m not physically there.
The wiring and installation process would be the same as what you’d do for a half-switched or split circuit receptacle. That’s my point. The provided information isn’t sufficient to confidently say it’s not without additional details.
Also, you still haven’t explained where the mention of a disposal came from in the original post. You expect me to rely on your deduction skills, but you concluded that the outlet is for a disposal?
If you believe it’s for a disposal, one might assume it’s switched since you’d need to be able to turn the disposal off.
Alright, as I mentioned earlier, someone claimed that it might power a garbage disposal, did I say it was you? No. You would need to be present to verify if it was indeed switched. The original query was about installing a GFI in what they referred to as a kitchen outlet. So, technically, that goes against code, right? Mentioning that it could possibly be a switched circuit doesn’t really address the main question. It wouldn’t be too difficult to check if it was switched, but the author never mentioned anything about a switched outlet.
If you had to be present to confirm if it was switched or not, then how did you confirm that it wasn’t when you’re not there?
Claiming that you know what it is without actually knowing only adds confusion to the discussion.
There’s no violation in adding GFCI protection to this outlet.
They didn’t mention if it was switched, but the details they provided indicate they might not have the necessary knowledge, which is why there are questions.
Telling them something is true when you’re unsure doesn’t offer much help.
In my area, if there’s a split receptacle in the kitchen, you can’t have a GFI installed. I’m assuming it’s a split receptacle because it’s in the kitchen. As mentioned earlier, the author could clarify if it’s switched or not. You’re absolutely right, if it’s not a split receptacle, then it’s fine, and it would comply with code.
And what rule would prevent a split receptacle in the kitchen with GFCI protection?
It’s definitely not against code to do that.
You can’t physically install a GFCI receptacle as a split feed, but there’s no rule against using a GFCI breaker.
The poster might have more information, but what you said before was incorrect. That’s the main point of this discussion…
You claimed it wasn’t a switched outlet and started talking about a disposal.
You’re right, it could be a switched receptacle depending on its location. However, since the person asked about replacing and installing the GFI, you could technically install it. Is this up to code? Adding the GFI removes one feed from the plug, which was originally designed to have two separate breakers (if it’s a Kitchen plug). Since the pictures are not clear, we can’t say for sure if it’s an old-style kitchen plug. It’s unlikely that they would be able to install a GFI breaker if they are asking this question. More pictures are needed to determine the location and if it’s switched or fed directly from the breaker, but we don’t have them. Advising them to cap off one of the lines and add the GFI would be misleading.
This used to be a common practice, but maybe not anymore. You might still be able to do it by connecting the breakers with a handle tie. The voltage is out of phase by 180 degrees, so the neutral only handles half of the unbalanced load.
This seems to be a simple connection to another outlet or plug that remains powered when this GFI is tripped since they are on the same circuit (controlled by a single breaker). In some cases, people opt to use a 12-3 wire for this specific scenario to identify any components that lose power when the breaker is switched off.
To make the second outlet trip with GFI, connect the red wire to the top (line).
Suggests treating it as if it is an outlet downstream? It’s a bit challenging to visualize that concept.
This is actually a multi-wire branch circuit and it meets code requirements… A GFCI receptacle won’t function in this setup, unless you isolate the red wire and only utilize the black one (or vice versa). You do have the option of using a GFCI breaker instead.
The red wire is for a switch. This is likely a half-switched plug, most likely for your dishwasher or disposal.
How can you be sure that it’s meant for a switch and not just two separate circuits?
Always remember, if it’s inside a house (or an apartment), half of the plugs are switched every time! But if it’s on the countertop, the switch itself should be there, not an outlet (I’ve been working as an electrician since 1987)
Why the requirement for a switch? Could it be the two small appliance circuits on each receptacle instead?
On the countertops, there are only 2 circuits at 20 amps with GFCI protection. This rules out knob and tube wiring (which would require #10 cu capable of 30 amps). I’ll take a guess and say you might not have much knowledge about electricity.
You might not be aware that the code hasn’t always required the 2 SABC’s to be GFCI. Even if they were supposed to be, it’s possible that changes were made over the years. Have you considered the presence of a GFCI breaker for protection? Are you assuming the person asking is knowledgeable? If they were, would they need to ask these questions?
Is this #10 knob and tube wiring? While you may be correct, it’s hard to definitively rule out the possibility of it being a pair of circuits. It would be beneficial to determine if it’s a switched outlet (which is a bit unusual above a countertop), a tandem breaker, or something else.
I have been working as an electrician since 1987…I have witnessed many things, but not exactly what you are thinking of! It could be the switch or outlet for the disposal and dishwasher.
Interesting location for a disposal outlet. I find it surprising that you haven’t come across split receptacles using two circuits on a tandem breaker.
That’s why I mentioned that someone might have accidentally added a receptacle where a switch should be, and I have definitely seen that happen before!!!
It’s hard to pinpoint WHERE it is exactly, based on the pictures provided, as well!!!
I do know that sharing a neutral for small appliances could cause overheating and melting!!! So dividing circuits on 1 duplex isn’t the best idea, or recommended!!! Splitting circuits for bedrooms was common, before the arc faults became mandatory in 2000 (as mentioned in the 1999 NEC code book)
No one can accurately diagnose it just from a picture, regardless. All I’ve mentioned is what is typically done, and what isn’t, while looking at the same picture you all are…
Not sure where you all are, that a 20 amp circuit needs to be divided to run a coffee maker, a toaster, and a blender altogether?? 😂😂
Wait, how does a split receptacle on two circuits with a common neutral differ from a 120/240 circuit for, let’s say, a range?
Hey, are you talking about those 3-prong 50 amp outlets that have caused accidents??
The ground and neutral have to be separated on-site…
The 2023 code now requires it to be a 4-wire setup on a 50 amp GFCI circuit… it’s a safety risk!!!
I would bet that a previous homeowner messed up the installation but managed to get it working, after it kept tripping breakers (or blowing fuses, if the house is that old)
You can’t get homeowners insurance, or purchase a home with old 60 amp services though…
Also, you’d need 8 breakers for 4 countertop plugs, (every 4 feet) the way you’re explaining it, as a split plug!!! 60 amp services typically have 4 TOTAL branch circuits with a pair of 30 amp fuses for a dryer or AC compressor, and the pair of 60 amps as the main!!!
No, I’m talking about a 240 V motor that doesn’t have a neutral wire.
Where could you possibly find a 240V motor in a regular kitchen setup? You’re taking a guess based on a picture and clearly not understanding the situation… I think we can wrap this up now.
Hey there, ! Just to clarify, I’m not definitively stating what it is, just pointing out that it could be one of two valid possibilities. In areas where people have their own wells, it’s pretty common to come across 240 volt pumps, especially outside of heavily populated areas. And when it comes to woodworking enthusiasts, their table saws and jointers are often running on 240 volts.
Oh, and I’m aware that 240 is more of a nominal figure than an actual measurement in most cases. I was specifically curious about range circuits, where the load isn’t evenly distributed between the two legs like it is with a pump. It’s essentially like a three-wire circuit for split outlets, with a single neutral wire that’s the same gauge as the hot legs and works just fine in both scenarios. When I mentioned a three-wire circuit, I meant three wires plus the ground.
No way, do you even know what an electrician does??
Get out of here you clueless handyman wannabe
Yup, it’s pretty obvious you’re not familiar with the role of an electrician. 😂😂😂
Is absolutely right. We currently have 3 receptacles operating 2 circuits each
It’s clear that you have no idea about me OR my profession
Just keep moving with your group Handy Dan and the amateurs
So you’re not familiar with a three-wire branch circuit and can’t picture a household application for a 240-volt motor. That pretty much sums it up.
Never mentioned anything about not hearing of one… he simply stated it’s not common and there are 6 circuits on a kitchen countertop??
And an air conditioner compressor isn’t considered a “motor”
Do you consider yourself Edison?? Well, even he was considered a hack… which state did you obtain YOUR Masters license in?? Mine was issued in the Midwest
Clarified that he wasn’t talking about compressors but rather motors in table saws and jointers commonly found in home shops. It’s possible that this setup is common or not, but it’s important to consider other possibilities. Let’s move on from this discussion.
Mentions that welders are 240v and saws are 120v in single-phase homes. Industrial saws or motors in a shop wouldn’t typically operate on a residential single-phase system. It would usually require 3 phase 480. If you’re out of your depth, you may need inverters and buck/boost xformers to run equipment. We could have wrapped this up earlier, but I wanted to show you that you’re exceeding your knowledge in this area. No hard feelings, sir!
There’s always a bunch of bad advice on electrical posts.
The green arrow shows where you can make changes. On a duplex outlet, you can remove a small brass tab that connects two screws to give each outlet its own circuit or control them with a switch. A GFCI won’t do the trick here, so think about adding a GFCI/AFCI breaker to the fuse panel. If you prefer the look of GFCI outlets, swap it out for a decora receptacle, just don’t forget to break off the tab on the black and red side before turning on the circuit.
If you’re tackling electrical work, make sure to grab a non-contact tester and circuit breaker finder if you don’t already have them. The Sperry CS550A model is a solid choice for the finder. Together, these tools cost around $50, but they’re definitely worth the investment.
Look no further, this is the answer and solution you’ve been searching for.👆
You’ve likely heard this before, but it’s worth mentioning again. There are actually two circuits feeding into that outlet. The jumper between terminal posts is broken, causing the top and bottom plugs to be on different circuits despite being on the same device. Your GFI may have a way to remove the jumper, so make sure you reconnect the wires correctly – the home run should go on the line side, and anything it’s feeding should be on the load side.
Update: Yes, I managed to determine that there are 2 circuits involved. The outlet is powered by a double 15 amp breaker. There are no other appliances connected to this breaker. I wanted to replace it with a GFCI because it’s close to a sink. I’m not sure if I can find a GFCI breaker for this as the panel is 35 years old. I found a solution recommended by the Electrical Safety Authority. So, I will either follow that or cap off one of the wires.
Works as an electrician, and in my own home, I recently left the receptacle and didn’t bother with the gfi. I just make sure to avoid pushing my toaster into the sink when it’s on.
Gave me a good tip! It has been this way for 35 years before we moved in, and there didn’t seem to be any problems. I was just trying to update the outlets to more modern ones and thought I would add the GFCI to meet code requirements, but now it seems like more trouble than it’s worth.
It’s really not worth it because you’ll end up losing a circuit (red wire) and could trip breakers. The best move would be to run 12 gauge wires to the kitchen during a full renovation one day.
Understood. Sounds good, I’ll remember that for next time we do it.
Shared a creepy story about the previous owner dying by dropping her hair dryer in the sink. We didn’t want to freak you out with that info, though.
Always using scare tactics. Classic!
Haha, was totally joking with that one! I may not be an electrician, but I did install one in my kids’ sink area. Kids and water are always a risky combo!
I’m glad you were able to navigate through the confusion in the other comments about it being a switched outlet. It’s a shame they don’t offer dual/split circuit GFCI outlets. Your only choice is to switch out the breaker with a GFCI one or install a new 20amp circuit so it doesn’t have to be split to avoid overload like others have mentioned.
Attach it to the screw marked in green.
Instead of the red one, disconnect it at the breaker and stick to the dedicated 15 amp circuit. Chances are you won’t need more than that at once anyway.
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Seems like there are two different feeds sharing a neutral wire. See how the small metal bridge connecting the top and bottom outlets has been taken out. I don’t believe GFI’s are designed to work in that setup.
Hey there, putting in a GFI (Ground Fault Interrupter) in your kitchen is a smart move for safety. Normally, your GFI will have spots for a hot wire, a neutral wire, and a ground wire. If you see an extra wire, it might be another hot wire (as in a 240V setup) or a switched live wire for a separate circuit.
Here are a few things to keep in mind:
1. **Identifying the Wires**: Make sure you know the purpose of each wire. The colors may help, but it’s best to use a voltage tester.
2. **Checking Your Circuit**: If it’s a 240V circuit (less common in kitchens but still possible), your GFI needs to be compatible.
3. **Wiring the GFI**: Connect the ground wire to the ground terminal, the black (hot) wire to the brass terminal, and the white (neutral) wire to the silver terminal.
4. **The Extra Wire**: If it’s an additional hot wire, it might need to connect to another circuit or be capped if not in use. If it’s a switched live wire, it could be for a different circuit (like a garbage disposal or dishwasher).
If you’re unsure or the setup seems complex, it’s safest to consult a professional electrician. Safety always comes first, especially when dealing with electrical tasks in places like the kitchen!
Take care and best of luck with your DIY project!
Robert
I suggest removing the current box and installing a double gang remodel box. Connect the black wire as the Line on the GFCI outlet, purchase a standard outlet, and connect the red wire to the hot terminal. Share the neutral/white wire between both outlets.
You might want to consider contacting a professional. That minor error has the potential to cause a fire in your house, especially if you utilize those push-in holes at the back!
Connect the black and white wires and cap off the red wire.