April 2, 20233 yr 5 minutes ago, BritishRacingGreen said: Plenty. And to me it makes sense. The pv dc becomes part of the buildings electrical system, mainly due to the inverter being transformerless (Sunsynk / Axpert). So it make sense to protect this system using equipment grounding on the SPD. But the frame is a floating mechanical island with no reference to system ground (neutral) or equipment ground (earth). So a seperate earth does not comprimise system grounding routes. Just one issue is that the law does state that the earth rod must be bonded to utility earth. There is fortunately only ONE Earth. I have always used the utility earth with no issues. And if you live somewhere where there isn’t any utility earth then by all means use an earth rod.
April 12, 20233 yr On 2023/02/06 at 6:50 PM, Chris_S said: Getting a crazy headache thinking about this. Just say your PV wires or panels create a short to your rails and you touch your panels/rails or even climb on your metal roof you in trouble. So do you want that current to flow to your DB earth or to a ground rod? Most of us have fuses at the DC DB and not as close to the panels as possible. Is that current really going to go into the soil and not your body? On 2023/02/06 at 7:18 PM, YellowTapemeasure said: Take the human shock aspect out of it, and think about it as a fault only. Current returns to the source. It does not go into the soil / earth. It may use the earth /ground path to get back to the source. It will use anything that it can to get back to source. In a fault, the current will use the ground to get back to the source, creating a secondary path. Because there is two paths, there is less resistance (Ohm's law) and greater current, which hopefully trips the breaker / fuse. You honestly need to watch the video, from start to finish, and I say this respectfully. Get a notebook and a pen, and watch it from the beginning. You will thank Mike Holt later, I did. _____________________ This is giving me a headache too. I hear what you are both saying and also watched Mike Holt's video (a lot to take in as you said and perhaps I need another watch) but I still don't have clarity regarding the scenario @Chris_S has posed. I am having trouble understanding how a ground fault in the scenario Chris posed gets detected and cleared without the DC equivalent of an AC GFCI. Also don't see how a DC MCB will see enough fault current to clear the fault even if the negative PV cable is bonded to earth (bonded to rails of panels) since PV panels have a limited short circuit current and as per Mike Holt's video the only way to ensure a high enough fault current is via return to the source. Yet as per this article from Fluke's website arcing and ground faults can cause major problems such as the 2009 Bakersfield, California fire . Perhaps I am missing something but this seems to be a major risk with PV installations which is not talked about enough nor has a clear cut solution except for regular insulation tests and open circuit voltage tests as per Fluke's article... honestly who in the residential sector will actually do that apart from people on this forum? https://www.fluke.com/en-us/learn/blog/grounding/dc-ground-faults-pv-systems
April 12, 20233 yr 5 minutes ago, Star Harvester said: _____________________ This is giving me a headache too. I hear what you are both saying and also watched Mike Holt's video (a lot to take in as you said and perhaps I need another watch) but I still don't have clarity regarding the scenario @Chris_S has posed. I am having trouble understanding how a ground fault in the scenario Chris posed gets detected and cleared without the DC equivalent of an AC GFCI. Also don't see how a DC MCB will see enough fault current to clear the fault even if the negative PV cable is bonded to earth (bonded to rails of panels) since PV panels have a limited short circuit current and as per Mike Holt's video the only way to ensure a high enough fault current is via return to the source. Yet as per this article from Fluke's website arcing and ground faults can cause major problems such as the 2009 Bakersfield, California fire . Perhaps I am missing something but this seems to be a major risk with PV installations which is not talked about enough nor has a clear cut solution except for regular insulation tests and open circuit voltage tests as per Fluke's article... honestly who in the residential sector will actually do that apart from people on this forum? https://www.fluke.com/en-us/learn/blog/grounding/dc-ground-faults-pv-systems As a side note, I guess this is why we have Class II (double insulated), UV stable etc. cable for PV but after seeing how recklessly some installers run this cable, put it under strain, bury it raw under stones on flat roofs and bend it around sharp edges where conduit/trunking was cut etc. the double insulation does not give me much comfort...
April 17, 20233 yr 5 minutes ago, Treschen said: FYI from the sunsynk manual How do you interpret this - "grounded" as to a separate ground or "grounded" to the utility ground? Or maybe, the manual implies, the panels shouldn't be grounded at all?
April 17, 20233 yr Just now, PowerUser said: How do you interpret this - "grounded" as to a separate ground or "grounded" to the utility ground? Or maybe, the manual implies, the panels shouldn't be grounded at all? I understand it as grounded meaning connecting the DC negative from panel to earth,which you dont want. Solar panels should always be earthed afaik.
April 17, 20233 yr 3 minutes ago, Nexuss said: I understand it as grounded meaning connecting the DC negative from panel to earth,which you dont want. Solar panels should always be earthed afaik. That makes most sense!
April 17, 20233 yr 1 minute ago, PowerUser said: How do you interpret this - "grounded" as to a separate ground or "grounded" to the utility ground? Or maybe, the manual implies, the panels shouldn't be grounded at all? Its very vague, but best to put the frame on its own earth rod, earth wire straight in the ROD. Bring the live and neutral down and put use utility earth for those on your DC SPDs. You need a low resistance path to divert a lightning strike away from the inverter and if and wiring mishaps occur (on the frame). They don't want you to put your positive or negative directly to ground. (Essentially no earth bond for PV)
April 17, 20233 yr To add when we did my home install our Junior sparky decided to bring earth from the ROD that goes to the frame to the DC SPDs and the inverter was throwing faults during lightning after I investigated I had found what he had done and changed it. Slap on a wrist for him. We had to go out and change 2 installs that he was involved in. Lucky he was new in the team needless to say he had to sit through 4 hours of training with the master electrician and was supervised from start to finish for the next 5 installs. 😂
April 17, 20233 yr Author On 2023/04/02 at 11:29 AM, Modina said: All I can say to this subject is that if your electrician is required to perform earth measurements for the purposes of issuing a COC, I would recommend doing so after you had some good soaking rain. That should make the figures pass with flying colours. Otherwise you might need some very long earth spikes. Not so? This is true. A 2m earth rod in hard crusty ground will be useless
April 17, 20233 yr Some good info regarding earthing and lightning over here.... Earthing and Grounding | Lightning Protection | Exothermic Welding Supplier (lectrotech.co.za)
April 21, 20233 yr Goeienaand VirWat, (My vrou kom van Welkom, die weerlig daar is erg..) To accommodate the language-impaired, I will continue in British 😉 Good evening gents, Re: Lightning prevention. Should solar arrays perhaps grow metal whiskers to prevent lightning strikes? Any comment on "Dissipation Array Systems" (DAS) and "Charge Transfer Systems" (CTS)? From my reading these use different language but the same principles. . https://www.lightningprotection.com/...us-prevention/ . http://www.electrical-knowhow.com/20...on-System.html . https://www.oedigital.com/news/45744...ore-structures . https://zandz.com/en/lightning_prote...htning-strike/
April 26, 20233 yr Hi Treshen, if I understand correctly, I am with your "junior sparky" and also think earthing PV frames to a separate earth rod which also serves the PV SPD's makes sense. Several installs like that on our farm with both switching and transformer based inverters, many lightning storms, no problem. P.S: what is your opinion on lightning prevention instead of, or in addition to lightning diversion? Dissipation Array Systems (DAS) and Charge Transfer Systems (CTS) seems to use different language but much the same principles.
May 11, 20233 yr Almost 4 pages on this topic... Is the general consensus that one should stick a copper rod into the ground and connect the solar frame to the rod via a thick cable and then earth the DC output from the panels to the utility earth? This should make insurance happy so if there is a direct lightning strike, they will at least pay out.
May 15, 20233 yr On 2023/05/11 at 2:38 PM, PsyCLown said: Almost 4 pages on this topic... Is the general consensus that one should stick a copper rod into the ground and connect the solar frame to the rod via a thick cable and then earth the DC output from the panels to the utility earth? This should make insurance happy so if there is a direct lightning strike, they will at least pay out. Everyone happy with the above summary? One further question though. Can the panel frame earth wire (6mm2 ?) come down from the roof in the same galvanized conduit as the PV wires of my 4 strings?
June 1, 20233 yr How would you earth 2 separate strings of solar panels? Would you connect the frames of both strings together and earth with the same rod or use 2 different rods? And what size earthing cable is recommended? 10mm?
August 22, 20232 yr On 2023/06/01 at 10:43 AM, PowerUser said: How would you earth 2 separate strings of solar panels? Would you connect the frames of both strings together and earth with the same rod or use 2 different rods? And what size earthing cable is recommended? 10mm? I would connect the frames together with some earth wire and I recall it being mentioned earlier in the thread that one should use a minimum of 6mm earth. Edited August 22, 20232 yr by PsyCLown
November 9, 20241 yr On 2023/02/04 at 10:06 AM, Chris_S said: What is the SANS rules on this? Can panels be connected to house earth or must they have a dedicated earth spike. My home earth is connected to utility earth and a ground spike. Can I just use this existing ground spike? Can be connected to house earth or connected to ground rod separately not together as one might decrease value of another and create earth loop witch lighting love to find
February 2Feb 2 SANS requires exposed conductive parts to be earthed, but it doesn’t yet give a black-and-white rule specifically for PV frames. Proper solar bonding and grounding is important to ensure safety, protect equipment, and manage lightning-induced surges. Best practice seems to be bond all PV frames together, run a 6 mm² earth conductor to the PV DB or main DB earth, and if a separate earth spike is used for lightning dissipation, bond that spike back to the installation earth to avoid potential differences.Earth resistance should be verified with a tester (typically aiming for <6–12 ohms, depending on soil conditions). In the end, compliance comes down to what the registered electrician is prepared to sign off on for the CoC. Until SANS publishes clearer guidance, these practices remain somewhat of a grey area in South Africa
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.