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Thread: 240v grounded 3 phase

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    240v grounded 3 phase

    240v 3 phase delta. One phase is grounded. I am tapping off that system and putting in a fused disconnect. Two phases on fuses and the grounded phase labeled white not fused. Since the grounded phase and the grounding conductor were bonded in first disconnect do I do bond them together again in the 240v delta step up 480v delta transformer and to building steel. And since the 240v is grounded do I need to ground a phase on the 480v secondary and if so how would I do that in the step up transformer.

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    Quote Originally Posted by casjos View Post
    240v 3 phase delta. One phase is grounded. I am tapping off that system and putting in a fused disconnect. Two phases on fuses and the grounded phase labeled white not fused. Since the grounded phase and the grounding conductor were bonded in first disconnect do I do bond them together again ....

    No. 250.24(A)(5) still applies.. The grounded and grounding remain seperate..

    Quote Originally Posted by casjos View Post
    in the 240v delta step up 480v delta transformer and to building steel. And since the 240v is grounded do I need to ground a phase on the 480v secondary and if so how would I do that in the step up transformer.
    You can either ground one phase of the 480 output following the rules in 250.30, or you can make it an ungrounded system and comply with 250.21(B)
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    Why label the phase that has been grounded white? This conductor is not acting as a neutral, it's a phase conductor and an eg yes?

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    It is not a neutral, as you said, but it is a grounded conductor so I think identification is required per 200.6.

    I believe it is still a phase conductor, yet it is still grounded. Not a EGC at all.
    Last edited by jumper; 07-15-11 at 09:57 PM.
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    Corner grounds freaked me out the first time I saw one because I was so used to having a smaller voltage to ground than phase to phase.
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    Jumper, you are correct. Even though the grounded conductor in this case is not functioning as a neutral it still must be identified as one. I tried uploading a great graphic from iaei.org but it's too large and I don't know how to resize it, so here's the link to a most informative article

    http://www.iaei.org/magazine/2002/01...unded-systems/

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    Quote Originally Posted by mark32 View Post
    Jumper, you are correct. Even though the grounded conductor in this case is not functioning as a neutral it still must be identified as one. I tried uploading a great graphic from iaei.org but it's too large and I don't know how to resize it, so here's the link to a most informative article

    http://www.iaei.org/magazine/2002/01...unded-systems/

    People get confused with this in part because they don't always use the correct terminology. Many think of the 'white' as 'neutral'. Often times it is but there are times when it is not.

    NEC refers to it as a 'grounded conductor' for good reason. It is the conductor that is grounded. It does not always have to be 'neutral' to all other conductors of the system. Even a two wire transformer secondary does not have a 'neutral' but one conductor usually needs to be 'grounded'.

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    Quote Originally Posted by kwired View Post
    People get confused with this in part because they don't always use the correct terminology. Many think of the 'white' as 'neutral'. Often times it is but there are times when it is not.

    NEC refers to it as a 'grounded conductor' for good reason. It is the conductor that is grounded. It does not always have to be 'neutral' to all other conductors of the system. Even a two wire transformer secondary does not have a 'neutral' but one conductor usually needs to be 'grounded'.
    Exactly, that's why I am always mindful of the difference when making posts on here. On the other hand, when talking with the unexperienced I find that they get even more confused when you start using the term grounded conductor.

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    Quote Originally Posted by mark32 View Post
    Exactly, that's why I am always mindful of the difference when making posts on here. On the other hand, when talking with the unexperienced I find that they get even more confused when you start using the term grounded conductor.
    That is what the difference is between professionals and novices. A journeyman or higher level electrical worker, designer, engineer, etc. should know what a 'grounded conductor' is. There are many that don't. Majority of them seldom or never work on anything but 120/240 single phase also. They need to stay away from other systems if they are not willing to learn more about them. The basic concepts are still the same however you just need to understand what you have.

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    Grounded conductor
    Tom
    TBLO

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