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Thread: City Plan Checker Blues

  1. #1
    Join Date
    Apr 2018
    Location
    Encinitas Ca.
    Posts
    4

    City Plan Checker Blues

    Hello to all,

    I am new to the site and I was hoping to get some clarification. An AHJ 3rd party plan checker is telling me I have to upsize my EGC to #8 from #10. The system consists of 4 strings of 2 wire circuits each w/ its own 20a ocpd. The system is PV, Enphase(ac) IQ6+(240v no neutral) RS compliant. Being that it is an ac system is does not fall under 690 as per 690.6. I sized it larger than 250.122 calls for(#12). I ran all #10's, L1,L2 and Gr. However, I think the plan checker is conflating SSBJ w/ EGC.? Table 250.102(C)(1) NEC2017 calls for #8 if the largest current carrying conductor is smaller than a #2. Is he considering the PV system as the supply side? I realize this is debatable but I don't see the logic in it.? Even if he was, can he consider the EGC as the SSBJ? Again, I have to go back to 250.12(A), "egc's of the wire type shall not be smaller than specified in table 250.122, but in NO CASE shall they be required to be larger than the circuit conductors supplying the equipment." And finally there is the lighting factor. I can not find anything specifying conductor size in regards to it. Just vague statements like,"when necessary to comply w/ 250.4(A)(5) or (B)(4) the EGC shall be sized larger than given in the table". It seems to me that I've got this covered w/ the oversized #10.? Any input would be appreciated.

    JMW77-

  2. #2
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    9,603
    Quote Originally Posted by JMW77 View Post
    Hello to all,

    I am new to the site and I was hoping to get some clarification. An AHJ 3rd party plan checker is telling me I have to upsize my EGC to #8 from #10. The system consists of 4 strings of 2 wire circuits each w/ its own 20a ocpd. The system is PV, Enphase(ac) IQ6+(240v no neutral) RS compliant. Being that it is an ac system is does not fall under 690 as per 690.6. I sized it larger than 250.122 calls for(#12). I ran all #10's, L1,L2 and Gr. However, I think the plan checker is conflating SSBJ w/ EGC.? Table 250.102(C)(1) NEC2017 calls for #8 if the largest current carrying conductor is smaller than a #2. Is he considering the PV system as the supply side? I realize this is debatable but I don't see the logic in it.? Even if he was, can he consider the EGC as the SSBJ? Again, I have to go back to 250.12(A), "egc's of the wire type shall not be smaller than specified in table 250.122, but in NO CASE shall they be required to be larger than the circuit conductors supplying the equipment." And finally there is the lighting factor. I can not find anything specifying conductor size in regards to it. Just vague statements like,"when necessary to comply w/ 250.4(A)(5) or (B)(4) the EGC shall be sized larger than given in the table". It seems to me that I've got this covered w/ the oversized #10.? Any input would be appreciated.

    JMW77-
    Austin Energy has the same requirement, and I have fought that battle and lost. Since such a large portion of our systems are in AE's territory, we just use a #8 as a minimum size ground wire in every system. It's not that big of a deal.

  3. #3
    Join Date
    May 2011
    Posts
    4,261
    The plan checker might believe you need a GEC from the array, which is a minimum #8.

    They might be enforcing 690.47(D), perhaps without realizing it no longer applies to your code cycle. i.e. if you're on the 2017 NEC or equivalent, they may not have caught up to that section being changed to permit, rather than require, a GEC from the array. Or if you are on the 2014 NEC then it would be required.

    They might also have an interpretation of 250.4 that they think requires it. That's pretty out there, but I had an AHJ cite that section once.

  4. #4
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    16,801
    Quote Originally Posted by JMW77 View Post
    Hello to all,

    I am new to the site and I was hoping to get some clarification. An AHJ 3rd party plan checker is telling me I have to upsize my EGC to #8 from #10. The system consists of 4 strings of 2 wire circuits each w/ its own 20a ocpd. The system is PV, Enphase(ac) IQ6+(240v no neutral) RS compliant. Being that it is an ac system is does not fall under 690 as per 690.6. I sized it larger than 250.122 calls for(#12). I ran all #10's, L1,L2 and Gr. However, I think the plan checker is conflating SSBJ w/ EGC.? Table 250.102(C)(1) NEC2017 calls for #8 if the largest current carrying conductor is smaller than a #2. Is he considering the PV system as the supply side? I realize this is debatable but I don't see the logic in it.? Even if he was, can he consider the EGC as the SSBJ? Again, I have to go back to 250.12(A), "egc's of the wire type shall not be smaller than specified in table 250.122, but in NO CASE shall they be required to be larger than the circuit conductors supplying the equipment." And finally there is the lighting factor. I can not find anything specifying conductor size in regards to it. Just vague statements like,"when necessary to comply w/ 250.4(A)(5) or (B)(4) the EGC shall be sized larger than given in the table". It seems to me that I've got this covered w/ the oversized #10.? Any input would be appreciated.

    JMW77-
    I would just do it whether it is required or not. the cost difference is so small that you have spent more than the extra cost just typing about it here. Some things are worth fighting, some things not.
    Bob

  5. #5
    Join Date
    Apr 2018
    Location
    Encinitas Ca.
    Posts
    4
    I agree w/ just running the #8 in advance to prevent a slow down, unfortunately the system (11kw 3 strings) is already built w/ the #10 EGC and permitted just fine in Nov 2017. I am now adding 10 additional mods after the fact as per cust and the conduit is only 3/4" which works fine until I get to the last section of conduit before the run gets to the service. At that point I'm beyond the fill calc if I have to pull in a #8. Not to mention, I will have to rewire the switches on the roof(20a Hubbell) which means I will have to run #10 whips anyway to accommodate the switches. I realize these switches/disco's were not required unfortunately my AHJ does still require them(imaginary obstacles). I considered running a #6 bare externally to bond the racks and take it straight to the gr rod but the idea of doing that bugs me a little. It appears there is nothing requiring me to do this and if its going to be a bit of a pain and cost time, which is money, than I'd rather not.
    NEC.2017 250.122(a) states: "conductors of the wire type, shall not be smaller than shown in table 250.122, but in NO case shall they be required to be larger than the circuit conductors supplying the equipment".
    250.122(C)Multiple Circuits, states: "multiple circuits in the same raceway, shall be sized for the largest OCPD protecting conductors in the raceway." in this case 20a.
    250.4 seems a little vague, "likely to be energized" and "limit the voltage imposed by lightning"!! Really.. so he is saying that by going from the #10 to #8 it is going keep a lightning strike contained? I would love to hear Mr. Holt's opinion on that.
    250.4(5) shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a gr fault may occur"
    Sorry, didn't mean to rant, just tired of jumping through imaginary hoops. Thank you all for your input.

  6. #6
    Join Date
    Feb 2007
    Location
    USA
    Posts
    5,687
    If by chance this project is in CA , as a state we go by the California Electric code. We are on the 2016 version as of Jan 2017. ]
    I have not looked for the comparable CA code though.

  7. #7
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    9,603
    Quote Originally Posted by JMW77 View Post
    I agree w/ just running the #8 in advance to prevent a slow down, unfortunately the system (11kw 3 strings) is already built w/ the #10 EGC and permitted just fine in Nov 2017. I am now adding 10 additional mods after the fact as per cust and the conduit is only 3/4" which works fine until I get to the last section of conduit before the run gets to the service. At that point I'm beyond the fill calc if I have to pull in a #8. Not to mention, I will have to rewire the switches on the roof(20a Hubbell) which means I will have to run #10 whips anyway to accommodate the switches. I realize these switches/disco's were not required unfortunately my AHJ does still require them(imaginary obstacles). I considered running a #6 bare externally to bond the racks and take it straight to the gr rod but the idea of doing that bugs me a little. It appears there is nothing requiring me to do this and if its going to be a bit of a pain and cost time, which is money, than I'd rather not.
    NEC.2017 250.122(a) states: "conductors of the wire type, shall not be smaller than shown in table 250.122, but in NO case shall they be required to be larger than the circuit conductors supplying the equipment".
    250.122(C)Multiple Circuits, states: "multiple circuits in the same raceway, shall be sized for the largest OCPD protecting conductors in the raceway." in this case 20a.
    250.4 seems a little vague, "likely to be energized" and "limit the voltage imposed by lightning"!! Really.. so he is saying that by going from the #10 to #8 it is going keep a lightning strike contained? I would love to hear Mr. Holt's opinion on that.
    250.4(5) shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a gr fault may occur"
    Sorry, didn't mean to rant, just tired of jumping through imaginary hoops. Thank you all for your input.
    Can you claim the conduit as additional EGC?

  8. #8
    Join Date
    May 2011
    Posts
    4,261
    I would be asking why it was permitted 6 months ago and not now. What changed?

  9. #9
    Join Date
    Apr 2018
    Location
    Encinitas Ca.
    Posts
    4
    As far as the CEC, he cited NEC 690.47 and 250.166 as the reason for the correction. I had the client point out 690.6 and the fact that 250.166 relates to DC, he relented on that then dug around for awhile then came back with 250.64(c) so he is considering it a GEC. There is already a GEC #6 from service to 2 gr rods. The Enphase Q series microinverters do not require a GEC. Either way, if someone is aware of a code in the CEC that would negate the NEC in regards to AC PV systems in this particular matter I would sincerely appreciate a code # to reference. At the end of the day I can run the #6 bare externally if necessary as this at least would make more sense if you're trying to combat lightning than running a #8 through the equipment. It would be nice if I could get a reasonable explanation on why this is necessary. I never have a problem accommodating the code. I realize people smarter than myself are writing these codes but codes are comfortable because they are logical.. I just don't see the logic with this one. I wonder if someone over there has a few friends in the copper industry? Thank goodness they came to their senses for the 2017 cycle.
    For Reference:

    Enphase IQ Series Microinverters: Ground ConnectionsIn previous models, the DC input was bonded to ground through a GFDI circuit. This essentially groundedthe PV module’s output. This construction required connection from this point to the grounding electrodeusing a Grounding Conductor. However, since Enphase IQ Series Microinverters isolate the DC conductorsfrom ground, only a simpler Bonding Conductor is required. The Bonding Conductor is provided withinthe Q Cable system, which connects seamlessly to the AC power system output of the microinverter.Enphase IQ Series Microinverters detect ground faults in either the DC positive or negative conductor of thePV module by detecting the insulation resistance of each conductor to ground. Also contained in theEnphase IQ Series Microinverters is the Insulation Monitor (IM), which provides Ground Fault Protection(GFP) by measuring the insulation resistance of the DC circuit with respect to ground. Together, thesefeatures offer greater safety than previously possible in any inverter technology.

  10. #10
    Join Date
    Apr 2018
    Location
    Encinitas Ca.
    Posts
    4
    No change at all. Even the same plan checker! HaHa..

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