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    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
     
    #21

    Jan 21, 2013, 08:14 PM
    What's wrong if I have 120V on each leg to ground of a 240V circuit, but 6v between each leg?
    Could be a few different things.

    Is this a new installation, or existing?
    If existing, was it working before?

    What kind of breaker panel do you have? Possibly GE or FPE?
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
     
    #22

    Jan 21, 2013, 10:57 PM
    Technically, we could argue this multiple ways, Some of us know about 3 and 4 wire "single phase" 240 circuits.

    You don't have a 240V. You have two 120 V lines sharing an unconnected, in this case neutral. Each leg is in the same half of the cycle.
    We can add a few words to make it more technically correct.

    The point really being is that there are two "sides" of the 240 line and you have to have one from side A and one from Side B in order to get 240 Volts. If you have two side A's you will read 120 volts from both wires to ground, but not 240 volts across the pair.

    It is true that neutral and ground are connected at exactly one place for the premises. The service to the house can be looked at as a 240 V center-tapped transformer where neutral and ground are connected to the center tap.

    I kind of wish we could call this a 240 V bi-phase system, but we don't, The 120 VAC "sides" are 180 degrees out of phase with respect to ground/neutral.

    An advantage to this system is there is less of a shock hazard to ground. A disadvantage is that it causes a lot of confusion.
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
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    #23

    Jan 23, 2013, 06:06 AM
    If 1 side of a fuse or breaker is open, and a load is connected. You could read the 120 volts(same phase), going through the load. Try measuring with the load disconnected, you should have 120 volts between both legs and ground AND 240 volts between the 2 hots.

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