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Thread: 702.11 has me confused

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    702.11 has me confused

    702.11 says shall be gr. to electrode in accordance with 250.30. Its seperatley derived 250.30 c states gr rod nesessary, but 250.34 says portable generators not required to be connected to grounding electrode. This is an 8KW champion generator. So I'm wondering what is required? Its being inspected.

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    Portable generator. How are you installing it?

    -Hal

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    I should have added that of course, sorry, I'm using a generac manual transfer switch, it sws the nuet. has 8-10 circuits. That will be connectedto the loadcenter in garage which is a subpanel, running line to a 30amp 4W inlet box outside.

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    Quote Originally Posted by joebeadg View Post
    I should have added that of course, sorry, I'm using a generac manual transfer switch, it sws the nuet. has 8-10 circuits. That will be connectedto the loadcenter in garage which is a subpanel, running line to a 30amp 4W inlet box outside.
    So you're taking circuits out of the garage panel running them to the MTS and from there to the loads?
    Sometimes I don't know whether I'm the boxer or the bag.

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    Quote Originally Posted by joebeadg View Post
    702.11 says shall be gr. to electrode in accordance with 250.30. Its seperatley derived 250.30 c states gr rod nesessary, but 250.34 says portable generators not required to be connected to grounding electrode. This is an 8KW champion generator. So I'm wondering what is required? Its being inspected.
    A grounding electrode is not required since it's a portable generator. Per 250.34 (A) (1) And (2)
    Sometimes I don't know whether I'm the boxer or the bag.

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    thats correct roanoke. I am aware of 250.34, yet 702.11 states shall be grounded to electrode as per 250.30, so, a little confusing

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    702.11 overrides and/or modifies 250 so it shall be grounded to a grounding electrode. That doesn't mean you have to drive a ground rod, you can attach a 2500.66 sized bonding conductor to the exiting building grounding electrode system and ensure that the neutral and the ground of the generator are bonded together.


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

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    I've never installed this configuration, but I was under the impression that for a generator size specified by OP, as long as the TS does not switch the EGC, then the connection of the EGC through the TS to the ground bar (connected to a GEC) should be sufficient.

    But I'm ready to be schooled otherwise.

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    Quote Originally Posted by JPinVA View Post
    I've never installed this configuration, but I was under the impression that for a generator size specified by OP, as long as the TS does not switch the EGC, then the connection of the EGC through the TS to the ground bar (connected to a GEC) should be sufficient.

    But I'm ready to be schooled otherwise.
    It switches the grounded conductor so there would not be a grounded conductor on the generator.


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    I've read the section on generators probably twenty or more times, and still come away with a brain swirl. I try to look at the theory of what is being accomplished, and then back that into what they are trying to say.

    The primary purpose of the neutral/ground bond is to clear a ground fault involving the source. When the source is the generator, the difference between SDS and Non-SDS is where the EGC connects to the neutral to get back to the source.

    In an SDS, the bond occurs in the generator. The fault rides the EGC back to the SE ground bar, and from there rides the EGC of the cable connected to the generator (that is connected to the SE ground bar) all the way back to the generator, jumps to the neutral via the bond in the generator, and completes the low impedance path to clear the fault.

    In a non-SDS system, the fault rides the EGC back to the SE ground bar, and jumps to the neutral bonded at that point, riding this "un-switched" neutral of the cable connected to the generator back to the generator completing the low impedance path to clear the fault.

    Note that in both the SDS and the non-SDS connections described above, the EGC of the structure lands on the SE ground bar. And it is to this ground bar where the GEC is connected, and subsequently connected to the GE system. Pray tell me, why would the SDS system described above require any additional GEC connections than those that already exist at the SE ground bar? In both cases, any non-source current induced in the structure (from lightning or what not) are going to ride the EGC back to the SE ground bar....and from there to the GEC and to the GE. The fact it's an SDS on non-SDS is agnostic when it comes to non-source fault landing on the ground bus.

    I "think" all the mumbo jumbo in the NEC, when it's all laid out, is trying to tell us exactly what I said above, for a system as described by the OP. The reason it's worded all spaghetti-like is that it has to cover any and all SDS type configuration, including those where my assumptions about the bus bar loading won't pan out. But for an 8KW portable, I can't fathom any situation where the existing bus bar EGC/GEC/GES connections won't suffice for taking care of the non-source faults on the structure...be it SDS, non-SDS...or ahem....POCO itself!!!

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