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Thread: 240V Single -Phase Power Feed

  1. #1
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    240V Single -Phase Power Feed

    I have an EE that is specifying (3) #3/0 + #6G for a 200A power feed to a non-residential site. Shouldn't it be just (3) #3/0 (two hot and a ground), just like for power to a house?

    The only unique thing about this power feed is that the power is going from the meter and disconnect to an ATS first (ASCO model ATS-G-1PH-11BE-3R), then to the load center. I know that you can order the ATS with an optional full rated neutral configuration, but is the neutral lug on the ATS not necessary for this feed as the main panel accepts just two hot and a ground?

  2. #2
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    Assuming your disconnect at the meter has OCP then this would be a feeder. If there is no neutral load then the equipment ground is all you need past your service disconnect. That said, I would be surprised if the ATS or generator did not have a neutral load.
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  3. #3
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    Quote Originally Posted by FountainGuy View Post
    I have an EE that is specifying (3) #3/0 + #6G for a 200A power feed to a non-residential site. Shouldn't it be just (3) #3/0 (two hot and a ground), just like for power to a house?

    The only unique thing about this power feed is that the power is going from the meter and disconnect to an ATS first (ASCO model ATS-G-1PH-11BE-3R), then to the load center. I know that you can order the ATS with an optional full rated neutral configuration, but is the neutral lug on the ATS not necessary for this feed as the main panel accepts just two hot and a ground?
    Is this the service disconnect? If so you need a separate EGC run with the feeder to the panel. So you what then EE specified seems correct.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  4. #4
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    Yes. Power on site originates from 240V 1-PH meter, then to service disconnect, then to ATS, then to breaker panel (normal) and to diesel generator (emergency power).

  5. #5
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    Quote Originally Posted by FountainGuy View Post
    Yes. Power on site originates from 240V 1-PH meter, then to service disconnect, then to ATS, then to breaker panel (normal) and to diesel generator (emergency power).
    Thanks for clarifying that. Once you go past the service disconnect you need an EGC in each feeder but unless the transfer switch or panel require a neutral you do not need to install one.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #6
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    And the EGC for a 200A feed should be the same size as the 240V conductors, 3/0 in this case, correct? I had another site in which (2) #3/0 + #6G was specified for the feed and the county said that it had to be (3) #3/0 per 2017 NEC 250.24(c).

  7. #7
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    Quote Originally Posted by FountainGuy View Post
    And the EGC for a 200A feed should be the same size as the 240V conductors, 3/0 in this case, correct? I had another site in which (2) #3/0 + #6G was specified for the feed and the county said that it had to be (3) #3/0 per 2017 NEC 250.24(c).
    No, for the feeders EGC it can be sized according to T250.122 which would be #6 for 200 amps. Once you're beyond the service disconnect 250.24(C) has nothing to do with it.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    so no 120 vac loads?
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  9. #9
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    Quote Originally Posted by Ingenieur View Post
    so no 120 vac loads?
    Yes, there are several 120V loads in the load center. I'm just concerned about conductor sizes and quantity between the existing disconnect and the ATS, and then from the ATS to the load center and to the generator. I believe that (3) #3/0 + #6G is correct as the EE specified.

    I originally thought that it would be (3) #3/0 to the load center and that the third conductor is ground and the neutral doesn't become a neutral until the ground wire reaches the main load center. I don't have but two hot and a ground coming to my load center at my house and the neutrals and ground wires are on the same bus. My house has the main on the load center, which makes this conductor quantity/size different.
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  10. #10
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    A 200 amp, single phase, 120/240 volt feeder with 3-#3/0 and 1-#6 EGC is an extremely common installation.

    In your house your SEC's are 3 conductors, H-H-N, not H-H-EGC on the line side of the service disconnect.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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