GFCI and split circuits

Discussion in 'Electrical Forum discussion & Blog' started by moisheh, May 23, 2010.

  1. moisheh

    moisheh New Member

    Messages:
    42
    Location:
    Mexico and Canada
    I have seen this question on other forums but never saw a proper answer. Our kitched has 2 counter plugs that are split. One double breaker. Other than a GFCI breaker is there a way to utilize 2 common GFCI outlets??

    Thanks

    Moisheh
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,319
    Location:
    New England
    Don't think so. The way a GFCI works is it checks for the balance of incoming current on the hot leg with the outgoing current on the neutral. WHen the neutral is shared, there is likely to be an imbalance, and the thing would trip. I think to bring it up to current codes, you'd have to rewire one branch, and abandon the unused one.
  3. drick

    drick In the Trades

    Messages:
    392
    Lets see if I understand this correctly. By split you mean you have one outlet where the top half is on one circuit and the bottom half is on another circuit? If yes this is most likely illegal as the circuit is capable of delivering either 30 or 40 amps - probably the latter - to a outlet that is only rated for 15 to 20 amps.

    This should be easy to fix though. Since you have 2 outlets wired this way each one will have 3 wires - red, black and white. At the first outlet on the neutral side of the GFI connect the two white wires. On the hot side connect the two black wires. The two red wires are wire nutted together and not connected to the GFI. At the the second outlet the single white wire is connected to the neutral side of the GFI, the red wire is connected to the hot side of the GFI, and the black wire is just wire nutted and not connected to anything. All these connections are made on the LINE side of the GFI. Nothing is connected to the LOAD side of the GFI.

    When you are done each outlet is protected by one half of the 2 pole breaker and no GFI device will be capable of pulling more than 20 amps. You will no longer have a split receptacle with each half protected by a separate half of the 2 pole breaker, but thats a good thing.

    Oh, and the common neutral doesn't matter because its on the LINE side of the GFIs.

    -rick
  4. Lightwave

    Lightwave New Member

    Messages:
    98
    Location:
    Vancouver, BC
    Neither outlet can receive more than 15/20A provided the side tab linking the upper and lower hot screws has been snapped off. The common neutral can't be overloaded provided the hot wires are on different legs.


    @Moisheh:

    If you have a single receptacle that is split and fed from two circuits, you need a double pole GFCI breaker for GFCI protection. If you have two receptacles that are both split fed from two circuits, you could rewire the device boxes and install two common GFCI receptacles. If you rewire, neither outlet will be split and each GFCI receptacle will be on its own circuit. This may not be code compliant--I have no idea about Mexican requirements.
  5. moisheh

    moisheh New Member

    Messages:
    42
    Location:
    Mexico and Canada
    Lightwave: First I have to get rid of that Mexican Flag. We winter in Mexico but are Canucks!! There is one double breaker feeding the outlets. They are split at the location ( tab seperated). One electrician told me I need GFI breakers. The other said that if you sperate the netrals via a pigtail it will work. I also see both of these solutions via google. I am still confused.

    Moisheh
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,258
    Location:
    Cave Creek, Arizona
    REGARDLESS of the wiring, those two outlets can ONLY provide 15 or 20 amps depending on the circuit breaker. IT could provide 15 or 20 amps of 220/240 volt power, however, but that is NOT the same as 30 or 40 amps. Two GFCI's with separate hots and a common neutral will NOT phantom trip. Sharing the neutral with a different circuit AFTER the GFCI WILL trip the GFCI.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,319
    Location:
    New England
    It comes down to what's on the line side verses what's on the load side. Everything on the load (protected) side needs it's own dedicated hot and neutrals when you install a GFCI. Stuff on the common (unprotected) or line side, would work as it does today, no problems sharing the neutral.

    Code requires any new or remodeled circuits to be brought up to current code, and in the USA, that requires GFCI for recepticles in the kitchen counter area, and, they should be 20A circuits (at least two).
  8. Lightwave

    Lightwave New Member

    Messages:
    98
    Location:
    Vancouver, BC
    Our electrical code has very specific requirements for kitchen outlets. Kitchen receptacles must be either 20A with both outlets on one circuit (e.g. standard wiring) or 15A split. In most provinces, GFCI protection is only required within 1.5m of any sink. If you want/need GFCI protection for your outlets, you must either use a dual GFCI breaker or rewire both outlets for 20A and use 20A GFCI receptacles.
  9. drick

    drick In the Trades

    Messages:
    392

    Your right, but you are missing the point. My comment has nothing to do with overloading the conductors. I was focusing on the overloading of the device. If you look at your standard duplex receptacle it should be clearly marked for 15A 125V operation. This is not per outlet. This rating is for the whole device. Therefore breaking the tab and connecting each outlet to a different breaker, even if they share the same neutral, is a code violation.

    -rick
  10. drick

    drick In the Trades

    Messages:
    392
    The DEVICE rating stamped into the average duplex receptacle is 125V 15A. Connecting a 2 -pole 15A 240V line with a shared neutral to it and snipping the tab would be illegal as it would clearly exceed the device rating.

    -rick
  11. Lightwave

    Lightwave New Member

    Messages:
    98
    Location:
    Vancouver, BC
    Code in Canada (where the OP is located) specifically requires dual circuit split outlets in kitchens. Canada's various code authorities don't consider the requirement unsafe.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,258
    Location:
    Cave Creek, Arizona
    The device still is only carrying 15 or 20 amps and removing the tab does NOTHING to overload the device, unless whatever you plug into it would OVERLOAD it even if it were a single feed. Using your logic, you could NEVER daisy chain receptacles because the downstream devices could overload the preceding ones. The WIRE is the limiting factor as to whether it is overloaded or not, which is why "back stabbed" devices will NOT accept 12 ga. wire for a 15 amp rated device, but you CAN have multiple wires connected to it.
  13. drick

    drick In the Trades

    Messages:
    392
    The device is carrying 15amps at 240 volts if it is fed by a 2 pole 15 amp breAker with a shared neutral. That exceeds the power rating of 15 amps at 125 volts by almost 100 percent. Personally I would not be willing to connect an outlet in this fashion unless it was clearly spelled out in the NEC that it is ok to do this. If there was a fire for any reason someone could point to the rating on the device and then claim that was the cause. Whether it was or not would be almost immaterial.

    And exactly how would the downstream outlets overload the 125v 15amp rating of the first outlet? If the entire circuit is protected by a 15amp 120v breaker you would never exceed the 15amp 125v rating of the first device.

    Rick
  14. drick

    drick In the Trades

    Messages:
    392
    Unfortunately I can't follow your link -probably the fault of my Ipad - I'll take your word for it. If it were spelled out in the NEC I would be ok with it here in the states.

    Rick
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,258
    Location:
    Cave Creek, Arizona
    IF there is a shared neutral there is NO 240 volt load, there are TWO 120v loads, and if you were to put a snap over ammeter around BOTH hot leads you would find a ZERO amperage reading, (NOT 20 or 40), but 15/20 amps on either one.
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