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Thread: OCPD new service

  1. #1
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    OCPD new service

    From what I've been able to dig up.. an OCPD is not required in this situation. (See pic)

    But if asked why is it not required there. Would the correct answer be...

    "Transformer secondary protection is not required for the following conditions:

    "For transformers with primary voltage greater than 1,000V at supervised locations, with the following maximum primary protection [Table 450.3(A)]:"

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  2. #2
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    Often the service transformer is under POCO jurisdiction and NEC doesn't apply.
    The diagram you show seems to fall under 230.31 and 230.71
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  3. #3
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    I agree with Augie so far.

    Is the conductors in question "service conductors" or is it secondary conductors of a "separately derived system"?

    The note on that drawing doesn't go with the situation if they are indeed "service conductors".

    If it is transformer secondary conductors (separately derived system), I'd have to dig a little deeper to verify what that note says. I'm fairly certain it is allowed like shown for secondary under 1000 volts with some conditions - basically feeder tap rules in 240.21.
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  4. #4
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    Quote Originally Posted by kwired View Post
    I agree with Augie so far.

    Is the conductors in question "service conductors" or is it secondary conductors of a "separately derived system"?
    Service Conductors.


    Is there any section in the code that states that the OCPD ahead of the wireway is basically not required?

    Thank You

  5. #5
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    Quote Originally Posted by Designer69 View Post
    Service Conductors.


    Is there any section in the code that states that the OCPD ahead of the wireway is basically not required?

    Thank You
    Look at 230.90(A) Exception No. 3

  6. #6
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    The rules in Article 450 only apply to the protection of the transformer itself, they do not cover the protection of the transformer conductors.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

  7. #7
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    Quote Originally Posted by don_resqcapt19 View Post
    The rules in Article 450 only apply to the protection of the transformer itself, they do not cover the protection of the transformer conductors.
    If the conductors in question are service conductors, which OP says they are, the transformer is POCO equipment and not covered by NEC.
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  8. #8
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    Quote Originally Posted by Designer69 View Post
    Service Conductors.


    Is there any section in the code that states that the OCPD ahead of the wireway is basically not required?

    Thank You
    No. If you put OCCPD ahead of the wireway - that OCPD becomes the service disconnecting means and there conductors in the wireway are no longer service conductors.

    Multiple service disconnecting means are allowed - general rule is up to six. Setup with wireway like in your picture is a common method of installing multiple disconnects for a single service.
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