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GFCI use

Discussion in 'Electrical Engineering' started by Rack, Jan 23, 2007.

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  1. Rack

    Rack Guest

    Conditions: A 3 wire run from a breaker box, with alternate phases used to
    feed two circuits. So, - two 20A circuits run on a 3 wire #12 cable.

    Question: Can a GFCI breaker be used effectively? The common white wire is
    handling the ground for both circuits (R/W and B/W). At this stage GFCI
    outlet(s) is planed, but changing a breaker would be easier and more
    encompasing.
     
  2. Guest

    | Conditions: A 3 wire run from a breaker box, with alternate phases used to
    | feed two circuits. So, - two 20A circuits run on a 3 wire #12 cable.
    |
    | Question: Can a GFCI breaker be used effectively? The common white wire is
    | handling the ground for both circuits (R/W and B/W). At this stage GFCI
    | outlet(s) is planed, but changing a breaker would be easier and more
    | encompasing.

    A 2-pole breaker would do it. The disadvantage is both circuits go off
    if either has a reason to trip the breaker.

    A pair of 1-pole breakers will not work. The reason is there is no way
    to consistently measure the neutral current to see if it is in balance
    with the hot current unless measuring both hot curents together, which
    is what the 2-pole breaker does.
     
  3. Rack

    Rack Guest

    Thanks Phil.
    Thats what I suspected and why the original intent to use individual GFCI
    duplexes. These are generally for kitchen circuits and I don't care to use a
    common trip device.
     
  4. ehsjr

    ehsjr Guest

    This works with 2 GFCI receptacles and a regular
    2 pole breaker:

    -
    |2| LINE LOAD
    |P|-Hot -----------------+ +------+-------}}--
    |O| | | |
    |L| [GFCI] [Recpt.]
    |E| | | |
    | | | +------+-------}}--
    |B| Neutral -------------+
    |R| | +------+-------}}--
    |E| | | |
    |A| [GFCI] [Recpt.]
    |K| | | |
    |E|-Hot -----------------+ +------+-------}}--
    |R|
    -

    You cannot use a GFCI breaker in a multiwire branch.
    Ed
     
  5. Rack

    Rack Guest

    Thanks "ehsjr".
    That is the coures chosen. GFCI duplex after the "split" to a two wire
    circuit at the first outlet. Same on the other 2wire leg.

    Rack

     
  6. ehsjr

    ehsjr Guest

    You can split off a 2 wire circuit anywhere on
    the multiwire branch - doesn't have to be the
    first outlet. I mention that, because while you
    may already know that, others may not.

    Ed

     
  7. Guest

    | Rack wrote:
    |> Conditions: A 3 wire run from a breaker box, with alternate phases used to
    |> feed two circuits. So, - two 20A circuits run on a 3 wire #12 cable.
    |>
    |> Question: Can a GFCI breaker be used effectively? The common white wire is
    |> handling the ground for both circuits (R/W and B/W). At this stage GFCI
    |> outlet(s) is planed, but changing a breaker would be easier and more
    |> encompasing.
    |>
    |>
    |
    | This works with 2 GFCI receptacles and a regular
    | 2 pole breaker:
    |
    | -
    | |2| LINE LOAD
    | |P|-Hot -----------------+ +------+-------}}--
    | |O| | | |
    | |L| [GFCI] [Recpt.]
    | |E| | | |
    | | | | +------+-------}}--
    | |B| Neutral -------------+
    | |R| | +------+-------}}--
    | |E| | | |
    | |A| [GFCI] [Recpt.]
    | |K| | | |
    | |E|-Hot -----------------+ +------+-------}}--
    | |R|
    | -
    | You cannot use a GFCI breaker in a multiwire branch.

    Unless it is a 2-pole breaker with the neutral passing through (some
    larger current 2-pole GFCI breakers don't provide a neutral terminal,
    such as the 60-amp one from Square-D). But the OP apparently wants
    to minimize common trips, so your example above is what he needs if
    he can do the two separate branches of 2-wire wiring following the
    GFCI receptacles.
     
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