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Thread: 400 amp electric utility meter

  1. #1
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    400 amp electric utility meter

    400 amp meter 120/208V three phase what is the typical incoming electric utility feeder cable sizes? Need to size bonding jumpers and grounding electrode conductors.

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    400 amp meter 120/208V three phase what is the typical incoming electric utility feeder cable sizes? Need to size bonding jumpers and grounding electrode conductors in service disconnect.



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  3. #3
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    Depends on some information.

    NEC wise if you are supplying multiple service disconnecting means - the (common) conductors only need to be sized per load calculation. Conductors to an individual service disconnecting means need to be sized according to the overcurrent device - which if a single 400 amp device is all you have then you need 400 amp conductors. But you could have say 2- 250 amp overcurrent devices yet a total load calculation of only 325 amps - any service conductor that supplies both disconnects only needs to be a 325 amp conductor, which would include supply side of meter.

    Now if you are asking what size conductor a utility company may install - it varies and is not based on NEC. I would quite often see 350 aluminum conductor (not paralleled, just one conductor per phase)used for this by a utility.

  4. #4
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    Not to mention that you say a 400 amp meter when actually you may be talking about a 320amp (continuous duty) meter. Usually at an actual 400amps service that would require a CT cabinet with CT meter.

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    Quote Originally Posted by mopowr steve View Post
    Not to mention that you say a 400 amp meter when actually you may be talking about a 320amp (continuous duty) meter. Usually at an actual 400amps service that would require a CT cabinet with CT meter.
    It says 400 amp meter on it?

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  6. #6
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    Quote Originally Posted by codequestion View Post
    It says 400 amp meter on it?

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    Service disconnect has 400 amps fuse as well

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  7. #7
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    Quote Originally Posted by codequestion View Post
    Service disconnect has 400 amps fuse as well
    Look at 310.15(B)(16) and select a 400 amp conductor. Could be 500 kcmil copper if the calculated load is 380 amps or less.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    Quote Originally Posted by codequestion View Post
    It says 400 amp meter on it?

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    Self contained class 320 meter sockets are rated 320 amp continuous, 400 amps non continuous. Several utilities I work with dont allow them on commercial services - you need a CT cabinet for anything over 200. For a single 400 amp service disconnect, the conductors would need to be sized for the load and the "next standard size down" from the OCPD rating. This means you could have 351 amps of conductor if it met the load calc. Often times for small commercial services I will provide conductors with the full rating of the OCPD. I might do parallel 250 AL for a 400 depending on various things of course.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  9. #9
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    Quote Originally Posted by infinity View Post
    Look at 310.15(B)(16) and select a 400 amp conductor. Could be 500 kcmil copper if the calculated load is 380 amps or less.
    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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  10. #10
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    Quote Originally Posted by codequestion View Post
    It says 400 amp meter on it?

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    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.

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