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Thread: Grounding Electrode at inverter

  1. #1
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    Grounding Electrode at inverter

    Hello All,

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    This is an image from an article https://www.homepower.com/articles/s...s-pv-grounding , does installing a grounding electrode to the inverter a code violation? are there any dangers in doing so? most of all inverter installation manuals that i've read don't specifiy this. What are your opinions on this? Please forgive me if this has been posted in a previous thread. Thanks!

  2. #2
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    Well, that article is a few years old. These days most inverters don't have a grounded DC conductor. Thus the inverter manual will only require equipment grounding, and not a grounding electrode conductor for a DC conductor. Grounding is done on the AC side as it would be for any other premises, and solar equipment is not is not treated as requiring any special grounding other than the usual equipment bonding. In the NEC, separate structures usually require their own grounding electrode, and in the 2017 NEC that applies to a structure built to support a solar array. I'll leave lightning protection out of it because that's a whole other ball of wax.

  3. #3
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    When I look at that, and forgive me because I am not used to thinking about it from the code book but as a handyman... and a radio amateur operator.. I see it as saying it wants a four wire install to the inverter and wants a second ground run to the grounding system for extra cover... like we ground the antennas before bringing them into the house. I could and probably am looking at it wrong but it is something I would consider on my own home. Especially with four antennas on my roof already.
    Student of electrical codes. Please Take others advice first.

  4. #4
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    That is an electrode not required by code, but permitted. The big deal is that it is bonded by the circuit EGC, not a normal bonding jumper.

    IMHO this is bad design, because earth currents caused by a nearby lightning strike could enter one electrode, travel via the egc and exit the other electrode. My preference is that all ground electrodes be bonded using normal bonding jumpers.

    -Jon

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    Quote Originally Posted by winnie View Post
    That is an electrode not required by code, but permitted. The big deal is that it is bonded by the circuit EGC, not a normal bonding jumper.

    IMHO this is bad design, because earth currents caused by a nearby lightning strike could enter one electrode, travel via the egc and exit the other electrode. My preference is that all ground electrodes be bonded using normal bonding jumpers.

    -Jon
    I agree.

    NEC does not prohibit supplemental electrodes - to anything. They do need connected to the EGC when connected beyond the service equipment, and a small EGC to a specific item may be subjected to high current during a lightning event.
    I live for today, I'm just a day behind.

  6. #6
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    NEC 250.54 allows as many auxiliary grounding electrodes as someone wants to put in. Since they are not bonded into the premises grounding electrode system there can be a voltage potential between the auxiliary grounding electrodes and the premises grounding electrode system that can cause problems under some circumstances. So it's really best to avoid them unless you are in an area that will be free from outside sources of induced voltages, lightning for example.

  7. #7
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    Quote Originally Posted by pv_n00b View Post
    NEC 250.54 allows as many auxiliary grounding electrodes as someone wants to put in. Since they are not bonded into the premises grounding electrode system there can be a voltage potential between the auxiliary grounding electrodes and the premises grounding electrode system that can cause problems under some circumstances. So it's really best to avoid them unless you are in an area that will be free from outside sources of induced voltages, lightning for example.
    They are still bonded to the EGC which is bonded to the GES. Yes there can be temporary voltage potential differences when there is a fault current flowing or during a lightning event.
    I live for today, I'm just a day behind.

  8. #8
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    Quote Originally Posted by kwired View Post
    They are still bonded to the EGC which is bonded to the GES. Yes there can be temporary voltage potential differences when there is a fault current flowing or during a lightning event.

    Aux grounding electrodes are not required to be bonded into the premises grounding electrode grid with a GEC, that's what I am referring to when I wrote that they are not bonded. Sure they are connected through other wiring such as the EGC but that is not what the NEC considers a bonded grounding electrode system.

  9. #9
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    Quote Originally Posted by pv_n00b View Post
    Aux grounding electrodes are not required to be bonded into the premises grounding electrode grid with a GEC, that's what I am referring to when I wrote that they are not bonded. Sure they are connected through other wiring such as the EGC but that is not what the NEC considers a bonded grounding electrode system.
    I might not have worded my reply clearly enough either. I agree they are not connected to the GES, but they are bonded via EGC's so there is equal potential between them until there is a condition where current is flowing.
    I live for today, I'm just a day behind.

  10. #10
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    Quote Originally Posted by kwired View Post
    I might not have worded my reply clearly enough either. I agree they are not connected to the GES, but they are bonded via EGC's so there is equal potential between them until there is a condition where current is flowing.
    You are correct. From the NEC perspective, it's really a design and installation issue. GEC and EGCs are sized differently because they have different current carrying requirements and the installation requirements are different. Under non-fault conditions, they both provide a way to equalize the potential between the electrodes. But under the different fault conditions they are each designed for they can provide different responses so they are not equivalent in function.

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