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Thread: 400 amp service grounding

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    400 amp service grounding

    I am bidding my first commercial job and i know that i need to run #2 copper for my 400 amp service. I never ran grounding for a 400 amp service. what is the recommeded way to attach to ground rods and water line? thank you
    Last edited by CharlesLindell; 05-06-19 at 12:59 AM.

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    Water line uses a typical pipe ground clamp, and rods a typical rod clamp:

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    Maybe I don't understand the question?

    By the way, the wire to the rods never needs to exceed #6 cu.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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    Quote Originally Posted by CharlesLindell View Post
    I am bidding my first commercial job and i know that i need to run #2 copper for my 400 amp service. I never ran grounding for a 400 amp service. what is the recommeded way to attach to ground rods and water line? thank you
    I assume you have 2-200 amp panels instead of one 400 amp panel. I also assume you have a CT cabinet. If so we run the #2 and the #6 to the cabinet
    They say I shot a man named Gray and took his wife to Italy
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    Quote Originally Posted by CharlesLindell View Post
    I am bidding my first commercial job and i know that i need to run #2 copper for my 400 amp service. I never ran grounding for a 400 amp service. what is the recommeded way to attach to ground rods and water line? thank you
    Do you have a single 400 amp service disconnect? What size service entrance conductors?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by LarryFine View Post

    By the way, the wire to the rods never needs to exceed #6 cu.
    By code, but more often than not I see Electrical Engineer's require 250.66 size ground throughout.


    I know what I don't know, and I know where to go to find it!

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    I met up with the inspector at the job to go over things with him, since he will be inspecting it. He is requiring the 4oo amp service to have a 400 amp main panel, from there 2 200 amp sub panels. According to load, 500 cmils for service entrance is required. Meter is on the other side of wall. Service coming into the back of the panel.

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    Master electrician should know there are many ways to do this, many are correct, & since this is your bid your choice. Seems to simple of a ? for an experienced tradesman.
    CircuitRyder --- Unfortunately not all good ideas are code enforceable.

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    Quote Originally Posted by CharlesLindell View Post
    I met up with the inspector at the job to go over things with him, since he will be inspecting it. He is requiring the 4oo amp service to have a 400 amp main panel, from there 2 200 amp sub panels. According to load, 500 cmils for service entrance is required. Meter is on the other side of wall. Service coming into the back of the panel.

    So look at table 250.66 for 500 kcmil that will be the size for the water pipe. #6 is all that's required for a ground rod electrode.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by CharlesLindell View Post
    I met up with the inspector at the job to go over things with him, since he will be inspecting it. He is requiring the 4oo amp service to have a 400 amp main panel, from there 2 200 amp sub panels. According to load, 500 cmils for service entrance is required. Meter is on the other side of wall. Service coming into the back of the panel.
    With double lugs on the meter load terminals, two 200a mains would also work. His single 400a main "requirement" is not reflected in the NEC.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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    Quote Originally Posted by CharlesLindell View Post
    I met up with the inspector at the job to go over things with him, since he will be inspecting it. He is requiring the 4oo amp service to have a 400 amp main panel, from there 2 200 amp sub panels. According to load, 500 cmils for service entrance is required. Meter is on the other side of wall. Service coming into the back of the panel.
    Quite a bit of $$ can be saved using 230.40 exception 2 and just 2 200 A MB panels. Not sure if for some specific aspect of the job that isnt feasible, or its a case of an inspector "wanting" something that he doesnt have the authority to demand....

    Also, 500 copper is too small for 400 amps, unless you can use the next size up rule to get from 380 to 400 (sometimes inspectors want load calcs if you use that provision).
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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