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Neutral Conductor

  1. Oct 31, 2014 #1
    Neutral conductor.

    Where can I find information about strange installations sharing the neutral conductor between two different installations ?

    Best Regards
  2. jcsd
  3. Nov 1, 2014 #2


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  4. Nov 1, 2014 #3
    Running to see
    Best Regards
  5. Nov 1, 2014 #4
    Diagram it.... #1 activity
  6. Nov 2, 2014 #5
    Nice idea. I haved no much idea of possible combinations diagrams. But I will try in my next post.
    Best Regards
  7. Nov 3, 2014 #6
    When draw I fell is not possible.
    I assumed that are two differents installations.
    Each one with a electricity meter above.
    If these electricity meters are independent or not join above we don't close the circuit....

    Circuit 1
    electrical meter 1
    Phase 1
    Neutral 1

    Circuit 2
    electrical meter 2
    Phase 2
    Neutral 2

    If we use Phase 1 and Neutral 2 I think nothing happen.

    Except, perhaps, if the electrical meters are joined above.

    My confusion began with the shared neutral in a triphasic circuit. But this is completely different to what i was thinking....

    The circuit is not closed and nothing happen.

    Best Regards
  8. Nov 3, 2014 #7


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    Illegal by most code books these days for loads, but they do actually work and were used many years in the past. Actually, they are used quite often but in a different way.....

    You can obviously google it, but you can share a neutral between two loads in a single phase 240/120 house panel board for example.
    Meaning you can you one single romex and feed two loads like lets say two electrical outlets that both have their own breaker switch and sharing the neurtal from one romex. One wire of the romex (say the black) will hook in a 20 amp single pole breaker, then the other wire of the romex (say the white) will get wired into the 20 amp single pole breaker right beneath it....therefore they are 180 degrees out of phase, or you can say that each load is off of a different bus bar in the panel.

    The reason you can theoretically do this is that the currents are litterally out of phase, the sin waves are flipped. Therefore the current through the neutral never exceeds 20 amps do to the "crossing out" effect.

    You can see how the black and white wire is confusing. 30 years down the road the next guy comes in and does some rewiring. He doesn't know it is a edison circuit and re-wires it to a new load....except now he has line to line voltage....or 240 volts. Bad things happen when you hook 120 volt devices to 240 volt power supplies. For example, a light will burst, a vacuum cleaner will start on fire, a television will just plain fry...etc.

    Actually, come to think of it, the wiring coming from the transformer into your home panel is a edison circuit, but a legal one. They share the neutral, but the bus bars are 180 degrees out of phase. The source is a center tapped secondary from the nearest transformer. The wiring is ussually red and black with the neutral being white.
    Last edited: Nov 3, 2014
  9. Nov 3, 2014 #8
    If i understand well you can use a shared neutral in a triphasic installation. The same neutral for triphasic outlets and for the monophasic outlets
  10. Nov 4, 2014 #9


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    Yes, three phase can share a neutral as well if you are looking for 480/277 Volt for example, or 208/120 as another example.

    But typically, motors are powered by three phase with no neutral, just a 3 conductor plus ground if you will.
  11. Nov 4, 2014 #10


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    An electric oven also could have a somewhat simliar situation with single phase. It has line to line voltage with a neutral. 240 volt for the oven and 120 volts for the controls.

    The difference is that the breaker in the panel is 2 pole instead of the two separate single breakers mentioned above.
    The 2 pole breaker will be connected together mechanically.
  12. Nov 4, 2014 #11
    Best Regards
    In a car under DC is similar. the neutral is the ground.
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