How do I wire two GFCI receptacles with two separate circuit with a common neutral for dishwasher and disposal. I only have a 12/3 load wire and there is no way I can run another neutral.The kitchen is fully done. The gfci's getting powered from a two pole AFCI breaker but they sharing the neutral. I did a ton of research and have tried to connect many different ways but one of the GFCI always trips when both appliances are on. City requires both AFCi and GFCI protection. I'am using two pole AFCI breaker and a dead front GFCI receptacles just right underneath the electrical panel. Electrician said it won't work with out a second separate neutral. I have seen answers topics similar to this but I did't not find the one I am looking for. I somebody could provide a wiring diagram that would help a lot. I have learned that the GFCI's can't share the neutral on the load side, so I tried to use only the line side but then where I connect the only one load neutral? Or, What if if I swap the two pole AFCI to a two pole GFCI breaker and using two AFCI receptacles instead? It will be the same or I will be able do it? I would appreciate every help! Thank you!
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Those aren't separate circuits with a common neutral. They are one single circuit with two hots. The distinction is important. The proper name of that is "Multi-Wire Branch Circuit".– Harper - Reinstate MonicaCommented Dec 12, 2021 at 0:48
2 Answers
The electrician is correct, it is not possible to protect a shared-neutral multi-wire branch circuit like that with two independent 120V dead-front GFCIs.
A GFCI operates by monitoring for a current imbalance between hot and neutral; if you join two "load" neutrals together then current from one GFCI's hot will be able to flow back through the other GFCI (instead back where it came from) and look like a ground fault to both GFCIs.
Options:
Find a two-pole/240V combination AFCI/GFCI breaker for your panel, to use with the existing wiring.
Replace the entire run of /3 from the panel to load loads with wiring that has two separate neutrals (two /2s, /2/2, etc).
Instead of ripping out all the wiring between the panel and the kitchen, move the GFCI dead-fronts to the kitchen. Feed each with one hot and the common neutral; run dedicated hot and neutral to the loads.
If the disposal and dishwasher plug in, you may be able to replace their receptacles with GFCI receptacles (wired to "line" only, no "load" passthrough), if local code allows GFCIs to be located wherever those receptacles are.
If you really, really can't change the wiring and can't find a combination AFCI/GFCI breaker, you could perhaps instead swap out the box where you have the GFCI dead-fronts for a teeny-tiny "spa panel" size sub-panel. Feed it from the two AFCI breakers, and install a two-pole 20A GFCI. You'll need to handle-tie the AFCI breakers if they aren't already. No promises that this is code-legal or that your local inspector will approve.
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Thank you! Based on my research there is no two pole dual function breaker exist (Siemens). Yes it would the the easiest way to fix it. I can't run another 12/2 since the entire kitchen is done. Can't move the dead front in the kitchen either, there is granite backsplash with single outlet mud rings. Yes both appliances are plugin but can't use GFCI for DW and DP under the sink, thats why I put them next to the panel. Not sure what to do, I may look for the small sub panel option with a two pole GFCI breaker which I have.– ZeeCommented Dec 11, 2021 at 16:26
Simply use a 2-pole GFCI deadfront. Done.
What are you talking about Harper? There's no such thing.
Yes there is. Search "spa panel with 2-pole GFCI".
It's just a 2-space nano-service-panel with a 2-pole GFCI breaker in it. You can buy it pre-built, or assemble it from a GFCI breaker and a 2-space subpanel. The ampacity of the GFCI breaker does not matter.
And this can go right next to the service panel where you've been trying to install the two 1-pole dead fronts.
"That was easy"
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The spa panel with two pole GFCI breaker is not the same as the two pole GFCI deadfront. However they work under the same principal and it may be the only thing I can use with out making any major destruction in the kitchen. They should invent a double GFCI /AFCI outlets , it would help millions of people to save money. Thank you everyone for the answers!– ZeeCommented Dec 12, 2021 at 0:28
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@zee If your logic is "I want a 2-pole deadfront that's half the price of a breaker the way 1-poles are", 1-pole deadfronts are cheap because 1-pole GFCI receptacles are commodities. A 2-pole GFCI (socket or deadfront) would never be that kind of commodity. Now that NEC 2020 requires GFCI on some 240V sockets, they might start to exist, but still there'll never be enough demand to drive prices that low. Commented Dec 12, 2021 at 0:43
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Just to confirm, if I choose to use this spa panel with a two pole 20 amp GFCI breaker, the two hot feed for these breaker should come from the two pole AFCI breaker in the main panel along with the neutral which also from the load side of the AFCI breaker, that's correct?– ZeeCommented Dec 12, 2021 at 0:48
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Won't this approach depend on the AFCIs being the kind that don't require neutral to pass through / doesn't contain a sensitive GFCI for arc detection? If they're the kind that use GFCI internally to do arc detection, might connecting their load neutrals together cause immediate trips?– nobodyCommented Dec 12, 2021 at 1:05
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@Zee right... hots and neutral to the subpanel come off the 2-pole AFCI breaker in the main panel. Then your /3 cable for the multi-wire branch circuit attach to the 3 terminals on the GFCI breaker in the subpanel. Ground is carried separately both in and out of the subpanel, and does not connect to neutral in any way. Commented Dec 12, 2021 at 1:14