(IG) integrated grounding to be or not to be

So I am having an issue with some AHJ's and looking for clarification.

On IG railing systems such as Iron ridge, and Micro inverters (Darphon, ABB, enphase (IG) models) the specs call out that 6awg is not required for system rail GEC since the micro inverter is IG and rails are IG, which conducts GEC through the 12AWG branch circuit.

So do I need to use the 6AWG bare copper to ground IG rail systems, if the inverter manufacturers calls out that it is no longer required? I would assume that using weeb, or star washer between (IG) inverter and IG rail system makes it compliant to just use the 12AWG GEC found in the trunk and branch circuit, can anyone please clarify. 6AWG seems a bit redundant if the specs call out that it is not needed.

Kindest Regards

Comments

  • solar_davesolar_dave Solar Expert Posts: 2,348 ✭✭✭✭
    Re: (IG) integrated grounding to be or not to be

    Generally it is a tough row to hoe when going up against an AHJ. Good luck as they hold your fate in their hands.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: (IG) integrated grounding to be or not to be
    So I am having an issue with some AHJ's and looking for clarification.

    On IG railing systems such as Iron ridge, and Micro inverters (Darphon, ABB, enphase (IG) models) the specs call out that 6awg is not required for system rail GEC since the micro inverter is IG and rails are IG, which conducts GEC through the 12AWG branch circuit.

    So do I need to use the 6AWG bare copper to ground IG rail systems, if the inverter manufacturers calls out that it is no longer required? I would assume that using weeb, or star washer between (IG) inverter and IG rail system makes it compliant to just use the 12AWG GEC found in the trunk and branch circuit, can anyone please clarify. 6AWG seems a bit redundant if the specs call out that it is not needed.

    Kindest Regards
    The NEC calls for two types of wires that are grounded and not current carrying. (The neutral is grounded, but is intended to carry current during normal use, so we will leave that one out.)

    The two types are the Ground Electrode Conductor, or GEC, and the Equipment Grounding Conductor or EGC.
    The EGC is the one that usually runs with the current carrying wires of the circuit and is sized to match (but not necessarily equal) the current capacity of the circuit it accompanies. If the circuit wires between inverter and breaker panel or between solar panels and inverter are only #12, then a #12 EGC is all that is needed 99% of the time.
    The GEC is intended to carry fault current from the whole wiring system to the ground electrode or the Ground Electrode System (GES) if there are several electrodes.
    It can be expected to carry current from outside sources like lightning (not necessarily dire, and from faults all the way up at the service connection (higher current than any branch circuit.)
    So the GEC will be much larger and will typically be sized to the capacity of the electrode it connects to. For a simple rod electrode the maximum required by code (although you can use bigger) is #6 copper.

    The code also sometimes allows the same wire to serve as the EGC and the GEC for a particular run, and if that is the case, it must meet BOTH size requirements.
    The concept of Integrated Ground, as I understand it, is similar to the use of the conduit or other raceway as the EGC in a circuit. Namely, the metal parts are all bonded together in an approved way and so there is no need to run ground jumpers from component to component. It does not mean that the size requirements for a GEC are reduced.

    In the 2011 edition of the NEC, there is a specific provision (690.47(C)(3)) for combining the DC array GEC with the AC GEC and the AC EGC for the inverter. But even though the inverter AC wiring may be #12, the combined GEC/EGC that runs with them must still be #8 copper or larger, depending on what kind of electrode it eventually connects to. The section that specifies the size is 250.166. An inspector may still choose to require up to #6 or even #4 if he wants to, and 250.166 by itself does not prevent him from doing that.

    The IG system just keeps you from having to run a dedicated #6 to a dedicated DC grounding electrode. Have you actually checked the size of the GEC in the trunk cable? And from the trunk cable to the panel where the AC circuit is terminated?

    The Enphase documentation states that no separate EGC is needed for the microinverter because the DC circuit is isolated from ground and has a ground fault detector. That is fine for the DC GEC requirement for the microinverter itself. So all you really have in the trunk cable is the EGC at #12.
    But I have not yet found satisfactory support for there not being a requirement for DC grounding of the racking system. Point me to that, and you will have what it takes to argue with the inspector.

    In the 2014 NEC, there appears to be a requirement for a DC auxiliary grounding electrode and conductor for the racking, regardless of whatever else is being used. (And that DC rod electrode is not required to be bonded to the rest of the GES.) This provision is highly controversial and is being fought as being significantly less safe than either omitting this electrode or bonding it to the rest of the GES. There may soon be a Tentative Interim Amendment (TIA) to the 2014 NEC which reverses that requirement.

    The concept of IG is that there is no need for a DC GEC since the DC source can never energize the metal with respect to ground under any fault conditions. That does not necessarily cover other possible sources of energy which could affect the racking itself, independent of the fact that panels are mounted on it.

    As the electrical folk often say, there are two rules:
    1. The inspector is always right.
    2. When the inspector is wrong, see Rule 1.
    SMA SB 3000, old BP panels.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: (IG) integrated grounding to be or not to be
    inetdog wrote: »
    The IG system just keeps you from having to run a dedicated #6 to a dedicated DC grounding electrode. Have you actually checked the size of the GEC in the trunk cable? And from the trunk cable to the panel where the AC circuit is terminated?

    Enphase and ABB trunk cables for inverter systems less than 250 watts have a 12AWG EGC which is also considered the "GEC", since IG systems are defined as a form of under ground grounding according to NEC, in terms of the "integrated grounding" system. Enphase and ABB both point out that 6awg according to code is not required for IG systems, since the 12AWG EGC is the GEC. Sounds confusing doesn't it.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: (IG) integrated grounding to be or not to be
    Enphase and ABB trunk cables for inverter systems less than 250 watts have a 12AWG EGC which is also considered the "GEC", since IG systems are defined as a form of under ground grounding according to NEC, in terms of the "integrated grounding" system. Enphase and ABB both point out that 6awg according to code is not required for IG systems, since the 12AWG EGC is the GEC. Sounds confusing doesn't it.
    The words "integrated grounding" do not appear in the 2011 or earlier NEC, so that point is not crystal clear. And if it is not crystal clear, an inspector may well not agree with it. :)
    SMA SB 3000, old BP panels.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: (IG) integrated grounding to be or not to be

    Code is irrelevant in this case. It is as solar_dave says; necessary to do what the AHJ wants in order to get a pass on inspection. Arguing with them will just delay matters and probably cost more.

    So you put in the redundant ground wire, get certified, remove it for the wire value, and add a fee for dealing with officious bureaucrats.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: (IG) integrated grounding to be or not to be
    inetdog wrote: »
    The words "integrated grounding" do not appear in the 2011 or earlier NEC, so that point is not crystal clear. And if it is not crystal clear, an inspector may well not agree with it. :)

    But if I whipped out the 2014 NEC it is pretty clear :) If I really wanted to make the inspector look silly I could just run an ohm test on the IG racking/inverters to exceed 25ohms that would really put a frown on the inspectors face :)
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: (IG) integrated grounding to be or not to be

    Here is what is really grinding my gears...

    Some AHJ's follow 2010 california electrical code, not NEC.
    Some AHJ's follow NEC, some following 2008, 2011, or 2014.

    I swear the bureaucrats need to get organized!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: (IG) integrated grounding to be or not to be
    I swear the bureaucrats need to get organized!

    Oh please no; they're bad enough as-is!

    Educated, maybe. But you're not going to get EE's doing that job, even though some AHJ's are paid better than people with operable brains.
  • ARTsolarARTsolar Registered Users Posts: 14 ✭✭
    Re: (IG) integrated grounding to be or not to be

    The code reference that we run into when dealing with sizing the exposed EGC is 250.120 (C) which basically says that an EGC smaller than #6 AWG shall be protected from physical damage by a raceway or cable armor. Interpret "subject to physical damage" as you wish. So typically we will run a #6 to bond the rails and then splice to a smaller wire in a rooftop combiner.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: (IG) integrated grounding to be or not to be
    ARTsolar wrote: »
    The code reference that we run into when dealing with sizing the exposed EGC is 250.120 (C) which basically says that an EGC smaller than #6 AWG shall be protected from physical damage by a raceway or cable armor. Interpret "subject to physical damage" as you wish. So typically we will run a #6 to bond the rails and then splice to a smaller wire in a rooftop combiner.
    Even that has failure to interpretation because prior to the IG series of micro inverters enphase would allow bonding with an 8awg solid bare. Then at the end of instruction would say" at local jurisdictions discretion". The whole ground bond method is a joke. If it's designated as IG and inverters, metal conduit, junction boxes, are all bonded, and then in contact with 12awg EGC. It just makes bonding with 6awg solid bare a moot discussion as everything IG makes bonding contact without having to break the anodization of racking components. Whole reason why I switched from unirac to Iron Ridge. After awhile the weebs get annoying.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: (IG) integrated grounding to be or not to be
    ARTsolar wrote: »
    The code reference that we run into when dealing with sizing the exposed EGC is 250.120 (C) which basically says that an EGC smaller than #6 AWG shall be protected from physical damage by a raceway or cable armor. Interpret "subject to physical damage" as you wish. So typically we will run a #6 to bond the rails and then splice to a smaller wire in a rooftop combiner.
    Saying that anything smaller than #6 has to be protected from physical damage is not the same as saying that you can use smaller than #6 just because it is protected from damage even though some other section of the code requires a larger size wire. The issue in this case is whether a DC GEC is required at all, given the isolated/ungrounded nature of the DC circuit and the presence of a ground detector in the micro or string inverter.

    As you note, it does mean that even where a smaller than #6 GEC is approved by code, you have to make it larger if it is exposed to physical damage.
    SMA SB 3000, old BP panels.
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