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Thread: 400 amp electric utility meter

  1. #11
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    Quote Originally Posted by kwired View Post
    Does the meter plug in or bolt in?

    Plug in is what is called S base and is max 320 amps, bolt is K base can be 400 or 600 amps, though I have only seen about three or four of those in the wild, most POCO here are going to CT meter it if more then a 320 socket is necessary.
    K base

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  2. #12
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    Quote Originally Posted by codequestion View Post
    K base

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    So from what I can tell you are supplying a single 400 amp service disconnecting means from this meter?

    That will mean minimum conductor size you can provide per NEC is 500 copper (provided load calculation is not over 380 amps), parallel 3/0 copper, 700 aluminum (provided load calculation is not over 375 amps), parallel 4/0 aluminum (provided load calculation is not over 360 amps).

    As I mentioned earlier if utility is installing the conductor they may go smaller yet - many here would install 350 aluminum for a 400 amp service.

  3. #13
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    400A single and three phase meter base is pretty common where I have worked. In VA, POCO still provided for free. CT metering did not start till 600A.
    "Electricity is really just organized lightning." George Carlin


    Derek

  4. #14
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    Quote Originally Posted by kwired View Post
    So from what I can tell you are supplying a single 400 amp service disconnecting means from this meter?

    That will mean minimum conductor size you can provide per NEC is 500 copper (provided load calculation is not over 380 amps), parallel 3/0 copper, 700 aluminum (provided load calculation is not over 375 amps), parallel 4/0 aluminum (provided load calculation is not over 360 amps).

    As I mentioned earlier if utility is installing the conductor they may go smaller yet - many here would install 350 aluminum for a 400 amp service.
    Utility go smaller? They dont do 500kcmil or 3/0 awg. My original question was to determine size of bonding jumpers and grounding electrode conductors. Does one look at feeder cables on the load side to service disconnect or on line side the utility feeder cables to determine grouding electrode conductor and bonding jumpers in service disconnect?

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  5. #15
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    Quote Originally Posted by codequestion View Post
    Utility go smaller? They dont do 500kcmil or 3/0 awg. My original question was to determine size of bonding jumpers and grounding electrode conductors. Does one look at feeder cables on the load side to service disconnect or on line side the utility feeder cables to determine grouding electrode conductor and bonding jumpers in service disconnect?

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    GEC - look at heading in T250.66, it says "size of largest ungrounded service conductor or equivalent area for parallel conductors".

    250.102 table says same thing but is missing the word "service".

    I think if you are landing the conductor/bonding jumper in the meter you go by supply side conductor if they are different from load side conductor. If you are landing the conductor/bonding juper in the service disconnecting means - you go by the conductors that are between meter and service disconnect even if supply side of meter is different.

  6. #16
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    Quote Originally Posted by kwired View Post
    So from what I can tell you are supplying a single 400 amp service disconnecting means from this meter?

    That will mean minimum conductor size you can provide per NEC is 500 copper (provided load calculation is not over 380 amps), parallel 3/0 copper, 700 aluminum (provided load calculation is not over 375 amps), parallel 4/0 aluminum (provided load calculation is not over 360 amps).

    As I mentioned earlier if utility is installing the conductor they may go smaller yet - many here would install 350 aluminum for a 400 amp service.
    Now going back, the utility would provide 350kcmil for 400 amp k base meter assuming it is 400 amp service? Utility would not provide 500 kcmil or 2 sets of 3/0 awg?

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  7. #17
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    Quote Originally Posted by codequestion View Post
    Now going back, the utility would provide 350kcmil for 400 amp k base meter assuming it is 400 amp service? Utility would not provide 500 kcmil or 2 sets of 3/0 awg?

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    But if you install conductors between meter an service disconnect - you inspector is going to fail if you ran 350 because you must follow NEC, even though logic tells you 350 is probably not going to overheat if it will works for them on the supply side of meter. So now you have 500 or parallel 3/0 for service entrance conductors if you are running GEC to the service disconnect.

  8. #18
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    Quote Originally Posted by kwired View Post
    But if you install conductors between meter an service disconnect - you inspector is going to fail if you ran 350 because you must follow NEC, even though logic tells you 350 is probably not going to overheat if it will works for them on the supply side of meter. So now you have 500 or parallel 3/0 for service entrance conductors if you are running GEC to the service disconnect.
    Correct. I was talking about conductors from utility transformer to utility meter. I am also calculating short circuit fault at service disconnect and was wondering typical conductor size electric utility would install for 120/208V 3 phase 400 amps base k meter. Assuming thats 400 amps service.


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  9. #19
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    Quote Originally Posted by codequestion View Post
    But jumpers and grounding electrode sizes changes per nec 2014 aricle 250 based on largest unground conductor. I am after bonding jumper sizes and grounding electrode conductor based on 400 amp electric utility meter 120/208V three phase.

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    see 250.66 250.102(C)(1). You are going to have to nail down the conductor size before you will know what GEC size you will need.

    Edit: sorry this was already covered. I missed the whole second page of posts.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  10. #20
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    Quote Originally Posted by codequestion View Post
    Correct. I was talking about conductors from utility transformer to utility meter. I am also calculating short circuit fault at service disconnect and was wondering typical conductor size electric utility would install for 120/208V 3 phase 400 amps base k meter. Assuming thats 400 amps service.


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    350 aluminum seems to be common, but why not ask the utility in question?

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