Panel Frame grounding, the NEC and inspections

OK - looking for some advice here.

Some background:

My initial grid interactive system install involved a 1800 watt array on a tracker 120 ft from my utility room. The PV combiner box is at the utility room with a very short home run to the adjacent ePanel with inverter. That arrays panel frame grounding is done at the array with a ground rod. Other equipment grounding (metal enclosures, etc) is done through the service ground via the epanel ground bus bar.

The inspector who did the inspection of this initial install was fine with all of this.

Well now - a few years later I have added a second array - on a shed roof that is 140ft from the utility room (and about 200 ft from my first array). Again I grounded the panel frames with a ground rod at the array. Again, the circuit wiring from the array (4 pairs of 10AWG) runs some distance to a PV combiner box located this time about 25 feet from the ePanel - so there's a 25 foot home run (#3 and #4 AWG).

(There were several reasons for not placing the combiner box at the array but I don't think it's important for the question at hand).

So, here's the problem.

I've finally gotten around to getting my second array addition inspected (so that I can qualify for the WA state incentive payments) and unfortunately the previous inspector is no longer here. :cry: In his place the lead electrical inspector arrived and unfortunately - he a "by the book" kind of guy and admittedly does not have experience inspecting grid interactive solar systems. He has several questions about the initial install and clearly had not seen many battery based systems or non strictly grid tied systems. After some discussion he said he would have to research things more - and get back to me.:roll:

Well after a few weeks of not hearing I emailed him and this was his reply:
I am sorry for the time delay , I am working on other things while making sure that I am correctly evaluating your project.

The one main thing that needs to be changed is a grounding conductor installed. 690.43 Equipment Grounding an equipment grounding conductor between the PV array and other equipment shall be required in accordance with 250.110 … Equipment grounding conductors for the PV array and structure shall be contained within the same raceway or cable or otherwise run with the PV array circuit conductors when those conductors leave the vicinity of the array.

We will need to see a grounding conductor installed from the array to the equipment in the main structure. Otherwise, I will complete the inspection in the main structure with the diagrams and information you have sent
:grr

So.... I really don't want to have to try and run another 140 ft length of 10 AWG through conduit to my PV combiner. The current 8 wires are running through 100 feet of 1 1/4" PVC and then transition via a jbox through 1" liquid tight to my crawlspace then run through about 30 feet of 1" metal flex to the PV combiner. It would a major effort to squeeze another conductor through all that. I do have some empty 3/4 PVC running parallel to the larger PVC underground to the jbox - not sure if running in that would qualify as "the same raceway".

What I'd really like to do is be able to convince him that the current method is safer and actually not in conflict with the NEC.

Reading 250.11 it says "Exposed, normally non-current carrying metal parts of fixed equipment supplied by or enclosing conductors or compenents that are likely to become energized shall be connected to an equipment grounding conductor......."

My argument would be that PV panel frames are not likely to become energized (except by a lightening strike which is why a local ground rod is better!).

I have very little experience dealing with electrical inspectors and would love to get the opinion of those with more experience. Am I tilting at windmills here? Any other suggestions for getting past his "by the book" mentality?

Any advice greatly appreciated!

in case it helps here is the diagram of the addition:

Attachment not found.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    All I can say is "good luck" as this is one of the sections of code that many of us just plain disagree with (the whole issue of it creating a likely path to introduce lightning to the interior of the building which is a bad idea).

    Any engineers want to volunteer to sign off on this?
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Panel Frame grounding, the NEC and inspections

    Your only other choice (that I see) is to do a direct burial of your grounding cable (i.e., bare 6 awg or similar, or insulated direct burial rated--but I would try uninsulated with the inspector first.... Tell him it is even a "better ground" and keeps the lighting from being directed into the home) in its own 18" minimum deep trench ("near" the original run--And you might install some new/empty conduit(s) since you have already trenched).

    -Bill "not a code guy, just and engineer who had to do the code dance for many years" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    Thanks guys- I guess....

    So - no one thinks the argument that PV panel frames are not likely to become energized is going to fly huh?

    I really wish the NEC would get their act together on this. We all understand that running a panel frame ground wire from a remote array into your house is only making things less safe, not more safe. I wish the was a way I could convince this inspector to see this.

    Bill, I don't think running a bare #6 through the ground will help. I already tried to explain how the #6 bare copper I have running from the panel frames to a 8ft ground rod next to the array is the best way to ground things. He seems more interested in the letter of the law.

    I have some 10 AWG THHN that I can run - I guess if he insists on a ground wire running to the PV combiner then the best I can hope for is to convince him to let me run it in the adjacent, separate conduit I already have in place.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    Are the wires from the array run in metal conduit? Part of the NEC allows such as a ground conductor; you might be able to convince him it applies here.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Panel Frame grounding, the NEC and inspections
    Are the wires from the array run in metal conduit? Part of the NEC allows such as a ground conductor; you might be able to convince him it applies here.

    Nope, PVC - at least for the first 120 feet or so - up to where it enters the home where it transitions to metal.
  • VicVic Solar Expert Posts: 3,112 ✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections

    Hi mtdoc,

    Sorry to hear of the inspection issue. Many times it seems that these things are at the whim of the inspector.

    If you cannot convince the inspector that alternatives are as good or better as those prescribed by him, ... Your 1" flex/LT iare only about 50% filled based on my older Code book for THHN cable. Would seem that it might be fairly easy to pull in the new 10 Ga ground wire and a replacement 10 Ga conductor for the wire used to pull in these two. Of course the more "turns" in the conduit, the more difficult this might become.

    YMMV, Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections

    There's actually a much quicker and easier solution, but I don't want to suggest doing something dishonest, just to satisfy an inspector. In my mind, your outside ground for the panel array is better than what they suggest.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panel Frame grounding, the NEC and inspections
    northerner wrote: »
    There's actually a much quicker and easier solution, but I don't want to suggest doing something dishonest, just to satisfy an inspector. In my mind, your outside ground for the panel array is better than what they suggest.

    Now, you wouldn't suggest doing something deceitful like sticking a foot of ground wire in each end of the conduit would you? I mean, the inspector might get out his meter and look for continuity. :roll:
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    Now, you wouldn't suggest doing something deceitful like sticking a foot of ground wire in each end of the conduit would you? I mean, the inspector might get out his meter and look for continuity. :roll:

    I didn't suggest anything, but the other part of the equation would solve that issue as well.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Panel Frame grounding, the NEC and inspections
    Now, you wouldn't suggest doing something deceitful like sticking a foot of ground wire in each end of the conduit would you? I mean, the inspector might get out his meter and look for continuity. :roll:

    LOL - yeah, i have to admit I thought about that one.:-) Continuity testing would be tough given the distance- but if he pulled on it real hard....

    Its a sad state of affairs when one even has to consider such things just because you wanted to do things the safest possible way.


    Vic - thanks for your suggestion. Yes - the problems is the turns. Several elbows - not in the 30 feet of flex metal but in getting there through the 120 feet of 1 1/4 PVC.

    In the end I'm sure I can do what he wants but it will involve a lot of work. It is extremely frustrating to contemplate this since I know there is no good rational for it. :grr
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    mtdoc wrote: »
    LOL - yeah, i have to admit I thought about that one.:-) Continuity testing would be tough given the distance- but if he pulled on it real hard....

    Its a sad state of affairs when one even has to consider such things just because you wanted to do things the safest possible way.


    Vic - thanks for your suggestion. Yes - the problems is the turns. Several elbows - not in the 30 feet of flex metal but in getting there through the 120 feet of 1 1/4 PVC.

    In the end I'm sure I can do what he wants but it will involve a lot of work. It is extremely frustrating to contemplate this since I know there is no good rational for it. :grr

    If I were you, I would fight to have that changed. It would be safer to keep the PV array ground outside, and away from your equipment. That is how changes come about, by taking a stand and pleading your case!
  • VicVic Solar Expert Posts: 3,112 ✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections

    mtdoc,

    OK, try to get the inspector to chznge his opinions.

    If there are only "several turns" in the 11/4" Rigid Sch 40 Pvc conduit, you ARE permitted 27 ea #10 AWG THHN cable from the old Table that is on the desk here. For that part of the run, this is about 30% of permitted fill ...

    You know much more about the conditions of this installation, so will not further try to second guess how easy one thing or another might be.

    Best of Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    Vic wrote: »
    mtdoc,

    OK, try to get the inspector to chznge his opinions....
    Best of Luck, Vic

    I am reluctant to jump in this far into the discussion (but that has not stopped me yet.)
    I tend to agree with the inspector for this reason:
    The ground rod is going to serve as a DC ground electrode, and will be the primary route for lightning induced currents. No problem with that.
    But that ground rod needs to be bonded to the other ground rods in the system by a bonding conductor.
    And since the panel frames certainly could become energized by up to 48 volts DC by an internal flaw (not 120V AC, that's for sure), you need to provide a path for that fault current that has a chance of tripping a breaker somewhere.
    A ground rod with 25 ohms of resistance (fine for lightning) is not going to carry more than 2 amps from your 48 volt system. Not enough to trip anything.
    An equipment grounding conductor, with a resistance of (hopefully) less than one ohm, on the other hand, could allow that fault to trip a breaker of fuse.
    Without going into each and every possible fault scenario, I feel that an EGC would be a good idea.
    And John Wiles would probably agree with that too.
    SMA SB 3000, old BP panels.
  • vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    inetdog wrote: »
    But that ground rod needs to be bonded to the other ground rods in the system by a bonding conductor.

    I certainly agree with that.... but don't you think that bonding them with #6 bare in the trench is a better approach than a green insulated cable in the conduit?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    inetdog wrote: »
    I am reluctant to jump in this far into the discussion (but that has not stopped me yet.)
    I tend to agree with the inspector for this reason:
    The ground rod is going to serve as a DC ground electrode, and will be the primary route for lightning induced currents. No problem with that.
    But that ground rod needs to be bonded to the other ground rods in the system by a bonding conductor.
    And since the panel frames certainly could become energized by up to 48 volts DC by an internal flaw (not 120V AC, that's for sure), you need to provide a path for that fault current that has a chance of tripping a breaker somewhere.
    A ground rod with 25 ohms of resistance (fine for lightning) is not going to carry more than 2 amps from your 48 volt system. Not enough to trip anything.
    An equipment grounding conductor, with a resistance of (hopefully) less than one ohm, on the other hand, could allow that fault to trip a breaker of fuse.
    Without going into each and every possible fault scenario, I feel that an EGC would be a good idea.
    And John Wiles would probably agree with that too.

    I can see the point of having it connected to the system ground in the event of a ground fault and could also prevent a fire from happening due to a short circuit in the panel.

    I think that if the panels are far removed from the rest of the system, there is little chance of an energized panel frame causing a problem. Lightning surges IMO are a much more serious risk, and best if you can divert the surges away from the home and it's occupants, and the sensitive equipment with a good local ground.
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    Panel frames are usually made of anodized aluminum, which is not conductive at the surface. Therefore, chances are slim to none that they can get energized, and, even if they do, touching them will not be harmful.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    Some people need to get out in the vans more.
    You can't beat real-world experience for seeing the flaws in the theories.

    Cariboo "40 years experience and counting" coot.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    mtdoc,

    Unfortunately, with respect to code, I think you are SOL. First 690.43 requires the EGC for panel frames, explicitly and without any exception if they are not "likely to become energized". Secondly, your system requires GFP, which cannot operate at the array without the EGC, right? (I'm not too familiar with the Midnight products, but I assume there's a GFDI in there somewhere).

    Finally, in the 2011 code, there is 690.43(F) which says the EGC "shall be contained within the same raceway or cable or otherwise run with the PV array circuit conductors when those circuit conductors leave the vicinity of the PV array." If you are not on this code cycle yet then Bill's burial idea may fly, but if you are then I wouldn't gamble on it.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    NorthGuy wrote: »
    Panel frames are usually made of anodized aluminum, which is not conductive at the surface. Therefore, chances are slim to none that they can get energized, and, even if they do, touching them will not be harmful.
    True or not, it's not relevant. The issue at hand is one of inspection and code, and module frames must be grounded for an installation to be code compliant.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Panel Frame grounding, the NEC and inspections

    Thanks for everyones input. Really appreciated.

    The issue of GFP is another whole can of worms which I won't open here. Suffice to say I've researched this issue and read multiple threads here and on Midnite's forum and also Bill's excellent paper to Wiles which points out the flaws in the NECs requirement on this.

    In response to Jaggedben, yes the Midnite CCs have an internal GFI to satisfy NEC. And as recomended by some here (and by unnamed Midnite employees) I will be disabling this by bonding my battery neg to ground once my inspection is done.:roll:

    So, I think I may try to convince the inspector to let it be as is but I am not optimistic. He really seems to be a by the book kinda guy.

    Hopefully,if he insists on a new grounding conductor, he'll be ok with me running another length o#10 stranded (which I have on hand) through the empty 3/4" PVC conduit which parallels my PV conductor conduit - running next to it in the same trench. Not sure if that will meet the requirement of "the same raceway" :confused:

    My question then will be how best to connect this to my PV frames. Currently I'm using WEEB clips to connect panels via Ironridge rails. The top of each rail has WEEB lugs which currently connect to the local array ground rod via a length of #6 bare copper runing across the rail ends at the top of the array.

    I could connect the #10 stranded THHN to one of these lugs (which are already bonded together with the #6 bare copper) then run this into the shed with the PV wires (which run through liquid tight) before entering a Jbox where it would then proceed through the 3/4" pvc to my house where it will join the PV wires at another Jbox before going on to the PV combiner box ground lug.

    Assuming he allows the seperate run in 3/4" conduit anyone see any problems with this method code wise? Would it be better to start with some #6 bare copper at the ground lug a the top of the array and then join this to the #10 stranded THHN with a split bolt at the jbox?:confused:
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    mtdoc wrote: »
    Hopefully,if he insists on a new grounding conductor, he'll be ok with me running another length o#10 stranded (which I have on hand) through the empty 3/4" PVC conduit which parallels my PV conductor conduit - running next to it in the same trench. Not sure if that will meet the requirement of "the same raceway" :confused:
    It may be enough to satisfy the inspector if he is feeling generous, but the PVC pipe is the "raceway", which is a very strictly defined term. So putting the EGC in an adjoining raceway is not what the code asks for.
    If you had wire inside the PVC which was rated for direct burial, then you could argue that it was not really wire in a raceway, just direct burial cable that happened to have a piece of PVC around it for mechanical protection. That might not fly either.
    SMA SB 3000, old BP panels.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Panel Frame grounding, the NEC and inspections
    inetdog wrote: »
    It may be enough to satisfy the inspector if he is feeling generous, but the PVC pipe is the "raceway", which is a very strictly defined term. So putting the EGC in an adjoining raceway is not what the code asks for.

    Yeah, that's what I'm afraid of. But please, someone explain to me why that would make one iota of difference safety wise?:confused:

    If you had wire inside the PVC which was rated for direct burial, then you could argue that it was not really wire in a raceway, just direct burial cable that happened to have a piece of PVC around it for mechanical protection. That might not fly either.

    Well, I have THHN running in the conduit -so that won't fly. :cry:
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Panel Frame grounding, the NEC and inspections
    mtdoc wrote: »
    Yeah, that's what I'm afraid of. But please, someone explain to me why that would make one iota of difference safety wise?:confused:

    I can see two iotas. Small ones, but that is what an iota looks like. :-)
    1. If the EGC is in a separate conduit, there is no limit on how far away it could be, and there would be a serious possibility that someone working on the system later would not be able to associate that EGC with the current carrying conductors it belongs with.
    2. If a large amount of fault current ends up flowing through the EGC and it is separated from the line conductors, the magnetic field produced will be much larger than if the wires are adjacent and will be more likely to induce damaging voltages or current in nearby conductors, and the inductance of the EGC will present a higher impedance path for the fault current which might delay the tripping of an OCPD.
    SMA SB 3000, old BP panels.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: Panel Frame grounding, the NEC and inspections
    mtdoc wrote: »
    My question then will be how best to connect this to my PV frames. Currently I'm using WEEB clips to connect panels via Ironridge rails. The top of each rail has WEEB lugs which currently connect to the local array ground rod via a length of #6 bare copper runing across the rail ends at the top of the array.

    I could connect the #10 stranded THHN to one of these lugs (which are already bonded together with the #6 bare copper) then run this into the shed with the PV wires (which run through liquid tight) before entering a Jbox where it would then proceed through the 3/4" pvc to my house where it will join the PV wires at another Jbox before going on to the PV combiner box ground lug.

    I'd basically forgotten that you have in fact grounded the panel frames to a rod. The real issue, then, might be complying with 690.47. Which would mean a #8 jumper from your rod at the array to the GES of your house. 690 is generally clear on this even if 250 isn't.

    What code cycle are you on?
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Panel Frame grounding, the NEC and inspections
    jaggedben wrote: »

    What code cycle are you on?

    I believe he said 2008.
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