Pole mount and grounding thoughts

Wanted to get some feedback on this...

I plan on running 6awg bare for equipment ground. Thinking about grounding rods at array then run bare copper in trench next to conduit for DC run, and then tie that 6awg bare inverters and panel to rod at house. Anyone see this as not the thing to do?

Are the WEEB clips good or are lugs like I plan to use better?

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: Pole mount and grounding thoughts

    I will be interested in reading the replies...

    Do you have a lot of ground strikes in your area?

    And was this a Grid Tied System or battery based (off grid or hybrid inverter) system?

    As I understand--You will be connecting the solar panel frames and frame work to the bare ground wire that then goes to local ground rod(s). You will not be connecting any DC to Earth Ground connections at the pole.

    Then you will run a bare ground from the rod(s) at the array back to your home's main ground point (rod(s)/water pipe, etc.). I am not sure this is a good/bad or don't care... I can see several sides to the question.

    Your home's neutral bus in the main panel is (will be) connected to the main ground point (rod) typically near your meter. And the rest of your AC chassis grounds will be attached via conduit/green wire to your normal house wiring.

    If you have a battery bank, then you have a choice of connecting the Green Wire earth ground (from the house ground rod) to the charge controller (if internal DC ground fault interrupter), or to an external ground fault interrupter, or to the DC battery negative bus (if no solar panel ground fault system is used).

    As I understand, you cannot connect both to the DC solar panel ground fault system and to the DC battery negative bus to the earth grounding.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,813 ✭✭✭✭✭
    Re: Pole mount and grounding thoughts

    Isn't your pole mount pole, metal (steel) and that is then embedded in concrete with rebar, creating a "UFER" ground system. 6 or 8 inch iron pipe should take a pretty good strike, and the concrete, loading the dirt with conductive ions, should work pretty well. Then you tie it to the other ground panel, and you have the potential for a mess. Argh !!
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    There a a few...

    GT no battery

    DC earth ground will also connect to ground rod at array.

    I guess my thinking after reading Homepower, SolarPro, and PV design books was that it would be better to tie the to areas together. The bare ground in the trench will cover 180' that seems to me to be a good thing, and tie into the rod already in place at house.

    This all may be overkill....

    Of course I'll install a DC and AC lightning suppresor.


    The main thing is safety for the system and costs, I'm up for whatever is cheap yet will work.
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts
    mike90045 wrote: »
    Isn't your pole mount pole, metal (steel) and that is then embedded in concrete with rebar, creating a "UFER" ground system. 6 or 8 inch iron pipe should take a pretty good strike, and the concrete, loading the dirt with conductive ions, should work pretty well. Then you tie it to the other ground panel, and you have the potential for a mess. Argh !!

    I have read that pipe in concrete is not a good ground. My poles are 5.5' deep and 28" wide. There is a gravel base and rebar welded to pipe that is in concrete.

    Originally I thought it would be more than enough...so you do not think tying the 2 areas together is a good idea.
    That would save me a bunch of bare copper if I didn't have to run it in the trench. All I will have at the array is the midnite solar combiner....
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Pole mount and grounding thoughts

    Are you also going to pull a green ground in the conduit? If so what size?
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    Yes will be pulling 6awg for all 8 conductors that I will use.
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: Pole mount and grounding thoughts
    stumpy40 wrote: »
    DC earth ground will also connect to ground rod at array.
    Can you explain this more?

    Normally, the only DC ground to solar panel +/- wiring is usually made at the GT inverter (through its green wire connection and DC Ground Fault fuse/setup). There should never be any reason to make a +/- to earth ground at the array (unless you are doing this through lightning suppressor--and even then--I think I would do this at the home near the GT inverter input instead of at the array).

    If you had the ability to disconnect the array from the GT inverter(s) and move the cable several feet away when a sever lightning threat was forecast (not during a storm)--That would be be best way to isolate the array and inverter from lightning damage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    I just mean that my 6awg bare copper will tie all panel frames, poles, and disconnects to grounding rod. Then my 6awg green ground in conduit will connect array disconnects to equipment at house....then to all cans and ground rod at house.

    This is why I ask...i get confused as heck thinking about it all. Everything else is relatively easy.
  • mike95490mike95490 Solar Expert Posts: 8,813 ✭✭✭✭✭
    Re: Pole mount and grounding thoughts

    I'm sort of stirring the pot here. I have a 10' deep, 24" hole, full of 25' of 8" sch 80 pipe, rebar and concrete, for my array mount. It is a splendid UFER ground, and yet, grounding wires are on the array, and follow the - & + thru 40' of conduit to the battery shed, where they pick up a 8' ground rod. I'm not happy with 2 grounds, but the inspector thinks hes happy. :(
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: Pole mount and grounding thoughts
    stumpy40 wrote: »
    I just mean that my 6awg bare copper will tie all panel frames, poles, and disconnects to grounding rod. Then my 6awg green ground in conduit will connect array disconnects to equipment at house....then to all cans and ground rod at house.
    To be honest--Other than code which may require you to carry a green wire with your +/- DC wiring--I am not sure where it would be connected out at the array (assuming the GT inverter is at the house).

    Personally, I would not carry the green wire from the home to the array and save the copper (if required by code, I would try to convince the inspector to let you not connect the end anywhere at the array).

    Any Green Wire connection at the array would just be in parallel with the 6 awg bare copper wire--which is much better grounded--and avoids pesky ground loops (especially those that may be energized by lightning).

    I do not see where I would suggest to connect the green wire. Not on the local exposed metal/conduit/breaker boxes. And definitely not at the negative or positive DC bus connections (solar array +/- grounding is a single point at ground fault interrupter common point).
    This is why I ask...i get confused as heck thinking about it all. Everything else is relatively easy.

    -Bill "been there, still confused" B. ;)
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    Thank you very much.....you made it clearer to me now.
  • MacawMacaw Solar Expert Posts: 36
    Re: Pole mount and grounding thoughts

    I am finding the grounding of the top of pole mount to ground, the utility ground, and the mechanics of grounding each panel and each piece of metal attached to the panels to be a major element of the design and installation of my 12 panel array. Here are a couple of comments to start with-
    A UFER ground by definition must include at minimum one (1) piece of rebar a minimum of twenty (20) feet long. Anything shorter and it is just rebar in concrete and does not meet the design specifications of a UFER. (No 90 degree bends allowed) That will most likely eliminate the UFER ground from top of pole installations (for code purposes).
    I attached a picture of my one line diagram that is my best rendition, so far, of my grid tie system. The "Green" ground wire, not shown on the one-line, attaches to the panel frames and all of the metal claptrap that they are attached to and travels with the current carrying conductors to the inverter. At the inverter the negative current carrying conductor is grounded and the "Green" ground hooks into the GFCI circuit.
    Out back at the array the steel mast and all that metal claptrap including the panel frames is grounded to a 8 ft ground rod which just so happens to be part of a ground "arc" which has one ground rod every 8 ft or so and leads back to the utility service ground. The utility service ground is galvanized and probably is not as good as the ground arc now attached to it. A third ground wire is attached to the utility ground and it goes to the Fronius IG inverter ground electrode terminal. All of the wires in the ground and attached to the ground electrodes are #4 and all connections CADWELD. The equipment grounds for the DC shutoff, inverter, AC shutoff and PV meter base are common. Hmmm need to think about that ground. More later about the challenges of using #6 solid to ground all this stuff 17 feet up on a 12 panel top of pole mount. There has got to be a better way.
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    Looks good Macaw....I'll post up pics of my finished project.
  • mike95490mike95490 Solar Expert Posts: 8,813 ✭✭✭✭✭
    Re: Pole mount and grounding thoughts
    Macaw wrote: »
    More later about the challenges of using #6 solid to ground all this stuff 17 feet up on a 12 panel top of pole mount. There has got to be a better way.

    Just don't splice that wire ! AFIK, they want it all one piece. But I know mine, on 15 panels, sure wasn't #6, more like #8 or #10.


    Mike
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    What I did was split the ground to both sets of strings. One inverter has continous for its 3 strings of 12 and the other inverter has it for the 3 strings of 11. So each inverter has continous loop. Its all I could do due to length the #6 bare comes in. Then each ties into ground rod at array.

    The equipment ground of course lands on the A term and B term goes to rod.

    I hope I did this correctly..
  • mike95490mike95490 Solar Expert Posts: 8,813 ✭✭✭✭✭
    Re: Pole mount and grounding thoughts
    stumpy40 wrote: »
    ......I hope I did this correctly..


    Your inspector will be sure to let you know! ;)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    HaHA....I'm pretty sure I have covered every possibly scenario. But your right...who knows when it comes to inspectors.
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    OK...so panels are up and inverters mounted. I have the ac disconnect installed along with subpanel. Waiting for electrician to wire in disconnect then subpanel.

    One last question on grounding. I have term A and D inside sma dc disconnect. Term A is from equipment ground and then I'm running Term B to the grounding rod. This sounds good correct? I have 6awg bare continuos for 1 inverter, and then another continous run for the other...both tying into acorn nuts on grounding rod.


    I understand that you can only ground/bond your service neutral in 1 spot. What does this mean exactly?

    Also what causes ground fault fuse to blow in the inverter? Is it mainly if you have a nick or such in insulation on one of the grounded conductors? Just curious
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: Pole mount and grounding thoughts
    stumpy40 wrote: »
    I understand that you can only ground/bond your service neutral in 1 spot. What does this mean exactly?
    Think of the power coming in from a Transformer (on the pole, from your inverter, etc.).

    For safety, utilities and homes will ground the center tap of a 120/240 VAC transformer. This insures that nothing (lightning, wire crosses out in the street, etc.) will ever bring the voltage inside your home more than 120 VAC above "ground". That grounded center tap transformer lead is your "grounded neutral".

    The reason to only ground it in one spot in your home is to prevent sharing current flow in the neutral wire and the safety ground wire.

    There are lots of reasons why this can be a bad idea (types of electrical failures, wire gauge ratings, etc.) and safety rules (ground conductors are designed to care fault currents and not to carry day to day loads--some paths may be through metal conduit, when you have parallel circuits like a washer and electric drier--the drier neutral current could go through the smaller washer ground path, etc.)...

    So, to prevent any "ground loops"--There is a grounded neutral block in the main breaker panel--and from that point one (sub panels) the neutral block is actually mounted on insulating plastic to make sure it does not touch the grounded metal box.
    Also what causes ground fault fuse to blow in the inverter? Is it mainly if you have a nick or such in insulation on one of the grounded conductors? Just curious
    As I understand, a Ground Fault Fuse or Circuit Breaker Setup will trip if there is a ground connection (green wire/earth fault, not the "-" negative terminal in the solar panel) to any of the + connections in the solar array).

    It will not detect a short in the solar array between the +/- solar panel terminals.

    Basically, when ~1-5 amps flows through the fuse between the "-" solar panel terminal to the green wire ground (this is the only solar array ground connection), this causes the fuse to pop and turn of the inverter/charge controller--Or in the case with a circuit breaker type--The 1-5 amp circuit breaker will also trip the + lead 60 amp (or whatever rated) breaker.

    You may also have false trips with a MPPT Charge Controller + ground fault fuse if you tie a green wire ground to the battery bank negative lead (as I understand the setups). So, for a Xantrex MPPT 60 amp charge controller, you only make one DC ground / earth ground connection (inside the charge controller, and not at the battery).

    And, you do not want to share one solar array with two or more MPPT charge controllers + ground fault system because of the ground issues (and MPPT controllers should never share one solar array--each needs to be connected to its own set of solar panels).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    Thanks Bill very, very helpful.

    I should have the grounding done this week, and once power is at the house.... will commission inverters and see how it goes.....I wish there was a way to test beforehand.
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: Pole mount and grounding thoughts

    Sometimes--Paying an installer for their knowledge (and the start up risk is on their dime) is worth the costs. ;)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    ....if that's the case then we shouldnt have forums to ask questions.


    I designed, installed, and almost have it done with 4-5 questions asked. How many questions would a first time installer have on their first project? I would bet equal if not more.

    Just my thoughts on your comment
  • BB.BB. Super Moderators, Administrators Posts: 30,633 admin
    Re: Pole mount and grounding thoughts

    I was not commenting on your lack of skills--I am am just saying that Installers can be worth their charges too... It is a personal choice.

    I am not an installer and do not work in the solar business--so I have no dog in this hunt.

    Could I have installed my GT system myself--probably--But I am getting too old to be on a 2nd story steep pitch roof. It sure looked confusing, but after watching the install--it all made perfect sense. When I bought my system, I actually had not yet found this forum. :D

    And, in my case, I am letting my installer do the hassles with my [should say "his"] solar panel vendor after >20% have failed in just over 5 years (should be a complete new 3.5 kW array).

    We have both end users (a lot) and installers (at least a few) here--Just a tilt of the hat to the professionals here that have helped their customers with GT and off grid systems.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    I understand. I talked with several and each one had a hard time answering my questions....so the logical thing to do was read, study and do it myself. My background is such that I had a pretty easy time of most of it. Of course there have been questions asked. Mainly just grey area in the NEC and such.

    I am thinking about getting into the business after doing this install. I have to say it looks great, and have no doubt it will perform just as well.
  • stumpy40stumpy40 Solar Expert Posts: 35
    Re: Pole mount and grounding thoughts

    System fired up...no issues with inspection. It's working like a charm. Thanks to all
    I really wasn't worried...LOL.
  • Peter_VPeter_V Solar Expert Posts: 226 ✭✭✭
    Re: Pole mount and grounding thoughts
    Macaw wrote: »
    I am finding the grounding of the top of pole mount to ground, the utility ground, and the mechanics of grounding each panel and each piece of metal attached to the panels to be a major element of the design and installation of my 12 panel array. Here are a couple of comments to start with-
    A UFER ground by definition must include at minimum one (1) piece of rebar a minimum of twenty (20) feet long. Anything shorter and it is just rebar in concrete and does not meet the design specifications of a UFER. (No 90 degree bends allowed) That will most likely eliminate the UFER ground from top of pole installations (for code purposes).

    Hmm, I think the UFER requirement is for 20 feet of conductor, not necessarily rebar.
    My electrician just made a large coil using 25 feet of 6awg copper wire and dumped that in the hole before we poured the concrete for the poles. The inspector was happy with that. We then ran bare 6awg between the poles through the trenches, about 20' between poles and 2 feet down, about 40 feet of horizontal grounding.

    The ground wire from the poles back to the house ran through PVC conduit.

    FWIW I could have done the wiring myself, but for grid tied setups my power company requires a licensed electrician do the work.
  • MacawMacaw Solar Expert Posts: 36
    Re: Pole mount and grounding thoughts

    Yes Peter I see that the code does not use the word "straight" or "unbroken" or single conductor in the description of a UFER ground. It basically says to use electrically conductive coated steel reinforcing bars each at least 1/2 inch in diameter and 20 feet continuous length, or consisting of at least 20 feet of bare copper conductor not smaller than 4AWG. The conductor must be protected by 2 inches of concrete. Zowie that means (by this particular interpretation of the code) that I could make a Ufer ground with 20 feet of #4 looped in 12 coils 6 inch diameter stretched out over a two feet length. One glob of concrete 10 inch diameter by 2 feet long with a #4 wire hanging out the end meets the wording but not the intent of the code. No criticism here just an example about how the Ufer ground is not very well defined in the NEC.
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