Solar panel grounding

PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
I rejuvenate an old thread, but it never showed up in the new posts list. So I start over. It's probably redundant, but I didn't find anything else close to my question.

I've become a pro with small wind generators, but am total nit wit with Solar. I've just ordered my first round of panels.

Here is the question.

What is the proper way of grounding panels?

I am planning on bolting the panels down, using dielectric grease to some solid rails. Then I was thinking of just attaching a ground loop to each rail. Then it's to my negitive side of my buss, and earth grounds. Does this sound like a good plan? Simple and clean. Not interested in all that fancy railing. I'm already on a 45* pitch.

Thanks in advance

Comments

  • mike95490mike95490 Posts: 6,440Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    Building Code, I believe, does not permit your version. Instead, there is supposed to be a long, continuous ground conductor, fastened to each panel, with a code approved device, at, and only at, the panel mfg's designated grounding point.
    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
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  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    i believe they may be requiring the rails to be grounded as well, but don't quote me. i don't agree with this as the pvs will act much like a faraday shield for the rails, plus the rails are usually connected to the pvs well enough that should it (lightning, emp, or whatever) enter a rail it would transfer to the pv as the least path of resistance to ground.
  • solarixsolarix Posts: 713Solar Expert
    Re: Solar panel grounding

    I like the Tyco Solklamp product. Not cheap, but none of the approved lay-in lug devices are. Wiley ground washers are cheap but most AHJ's don't go for them.
    Why don't the module makers build in a device? I would love it if there was a built in lug inside the frame (so it doesn't stick out and get in the way).
    Putting the lugs on is always a hassle and can't be prepped ahead because you can't stack the modules once the ground lug is sticking out and also can tear into the roofing etc. I'm sure it would be a lot cheaper for the manufacturers to build it in (weld in on) and they could ensure how it is used that way. Plus the current devices do a poor job of biting through the aluminum surface to make a good gas-tight electrical connection imho.
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding
    niel wrote: »
    i believe they may be requiring the rails to be grounded as well, but don't quote me. i don't agree with this as the pvs will act much like a faraday shield for the rails, plus the rails are usually connected to the pvs well enough that should it (lightning, emp, or whatever) enter a rail it would transfer to the pv as the least path of resistance to ground.

    I'm not familiar with the acumen's Niel. Forgive a rusty old man and define please? I'm a rookie on the solar side

    Thanks Guys. It's what I thought. There is no real standard. Some greedy went to the NEC and got their crap approved, raising the install costs bu tripple. There are allot easier and less expensive ways. And they wonder why more people aren't doing it.

    So far, my plan seems to be working the best
  • WindsunWindsun Posts: 1,164Solar Expert admin
    Re: Solar panel grounding

    Only the frames & mounting parts of the panels should be grounded where the panels are mounted, for lightning protection. The negative side should NOT be grounded where the panels are mounted. The negative is usually the grounded side, but it should be grounded where it terminates - usually at the inverter for grid tie systems. (Some microinverters use a positive ground, but that does not affect the panel grounding).
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    windsun translated that as it was the mounts that i was referring to.
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding
    Windsun wrote: »
    Only the frames & mounting parts of the panels should be grounded where the panels are mounted, for lightning protection. The negative side should NOT be grounded where the panels are mounted. The negative is usually the grounded side, but it should be grounded where it terminates - usually at the inverter for grid tie systems. (Some microinverters use a positive ground, but that does not affect the panel grounding).

    Now that's a new problem for me. I have wind also which has to be earth grounded as there is no other way. Unless you think the frames and grounding the inverters is suffucient
  • WindsunWindsun Posts: 1,164Solar Expert admin
    Re: Solar panel grounding

    The issue is not if it is earth grounded, but where. One of the biggest problems with a DC electrical ground at the panels is that you can get some really severe corrosion on any metal that touches the ground, due to it acting as one of the electrodes in the circuit. The problem is that you can end up with two different paths for the DC current - one of those through the ground, and since any metal touching the ground will act as either a cathode or anode, something will get corroded by stray DC currents. That is one of the main reasons for having a single point ground.
  • kevinkevin Posts: 9Registered Users
    Re: Solar panel grounding

    not all the solar panel need grounding, that dicide by the system inspection unit. somewhere will ask your system grounding.but in some special panel, just like thin-film with frame, they will ask the panel grounding for extend the life of the panel.

    skype ID:kevin_wang59
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Solar panel grounding
    kevin wrote: »
    not all the solar panel need grounding, that dicide by the system inspection unit. somewhere will ask your system grounding.but in some special panel, just like thin-film with frame, they will ask the panel grounding for extend the life of the panel.

    skype ID:kevin_wang59

    kevin,
    i think you lost me on this. what are you saying here? is it not all of the pvs need grounded or that only a part of a pv needs grounded? the 1st part is not true and the 2nd is impossible.

    i also have no idea what you are talking about as far as a thin film pv example as grounding does not extend the life of the pv unless it averted a lightning strike or an emp event. the only other incident grounding plays a part in pv life is the positive grounding sun power pvs require.
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding
    Windsun wrote: »
    The issue is not if it is earth grounded, but where. One of the biggest problems with a DC electrical ground at the panels is that you can get some really severe corrosion on any metal that touches the ground, due to it acting as one of the electrodes in the circuit. The problem is that you can end up with two different paths for the DC current - one of those through the ground, and since any metal touching the ground will act as either a cathode or anode, something will get corroded by stray DC currents. That is one of the main reasons for having a single point ground.

    You say single point ground. You mean just the mounting and the frames be grounded? Not the negitive side on the panels. I guess I can't protect my towers then.
  • BB.BB. Posts: 25,139Super Moderators admin
    Re: Solar panel grounding

    Read about Cathodic protection.

    And Cathodic Protection 101

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    Familiar with the zinc anoid process, but that doesn't answer my question
  • BB.BB. Posts: 25,139Super Moderators admin
    Re: Solar panel grounding

    Not sure what your question is... For Grid Tied systems, the Negative (or Positive for Sun Power panels) PV electrical bus is grounded to earth through a 1 amp fuse (typically). Not sure what is connected/grounded for tranformerless/non-isolated GT inverters that are just coming out now in the US (Europe has used these a bit longer).

    For a battery based system, typically we recommend grounding a permanent install to the negative battery bus--which is almost always carried through the charge controller (the PV- and Batt- are tied together inside most charge controllers).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    Thanks Bill

    I have a message in looking for some panels BTW.

    I have a simple system. KISS. I'm compiling all my connections on the roof at the switch up there, then coming down with 3/0 welding cable for 85 feet. From there I go to 800 AH 24VDC Battery bank and then off to 2 - Outback grid ties. (here we go again 2435 or 3524? LOL) They are earth/pipe grounded from the lug.

    Here's where i get my head scrambled. Feeble old minds

    My Wind Gennys are negitive ground to the towers. The tower is the negitive conductor. I am not supposed to go to earth with them, but can. Lightning protection is done at the inverters. NOW! I need to add Solar to this. I understand I need to ground the frames as the negitive is separate. So you are saying I should ground the negitive with a 1A fuse? Such a simple thing is so complicated. LOL
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Solar panel grounding
    Polaraco wrote: »
    You say single point ground. You mean just the mounting and the frames be grounded? Not the negitive side on the panels. I guess I can't protect my towers then.

    "Single point ground" refers to there being only one point where all grounding wires actually connect with the Earth. This can be a bit confusing too, because electrically it may be "one point" but mechanically there may be multiple ground rods (connected together in a particular way that allows them to "act as one").

    So what you are looking at is:
    A). A continuous wire running from panel to panel and secured to each by approved means which then goes to an Earth ground rod and;
    B). An appropriate wire from the battery negative only connected to an Earth ground rod and;
    C). An appropriate wire from the AC ground circuit connected to an Earth ground rod.

    Ideally, the last two Earth ground points mentioned should be the same rod and the first rod should be independent as it is more lightning/EMF protection than for circuit fault protection.

    Okay, that's just the "old school" basics. Unfortunately with MSW/PSW inverter issues (neutral-ground bonding), new NEC GFI rules for DC, particular site requirements, and the varying opinions on grounding rules vis-a-vis AHJ's interpretations it tends to get mind-bogglingly complicated. Adding lightning protection for circuits and you have even more issues.

    Nothing like discussing grounding to get the arguments started. ;)
  • BB.BB. Posts: 25,139Super Moderators admin
    Re: Solar panel grounding

    Just to be clear, the 1 amp fuse/breaker between battery "-" and earth/safety/green wire ground is an NEC requirement (sort of). I believe it is an unsafe practice. The original requirement was a method to reduce the chance of Arc Faults (only works to stop arc faults from "hot" to "earth" and no other--plus it can leave the power system in an unsafe state when the safety ground it "opened"). The problems with "opening" the safety ground are many and, I believe, greatly increase the chance of shock, fire, and injury if implement per "code".

    Note that www.midnitesolar.com (I believe) is coming out with DC Arc Fault Breakers--A much safer way to protect against DC Arcs (DC sustains arcs very nicely--much better than AC--So there is more of a chance of arc caused fires with DC circuits than AC).

    Anyway, with your solar array, whether or not you can use the tower as a ground conductor depends on what type of charge controller you have. There are a few (Xantrex XW 60 amp is one version) that measures the current from the solar array through its PV- to Batt- connection. Other brands/models usually do not.

    Personally, I would not tie the array "-" to the tower. I would bring it all the way to the charge controller. I think it keeps the wiring/current paths a bit "saner". Ground loops, issues of charge controller performance, etc...

    In the end, if you want to keep your wind turbine mounted to the tower and use it as your "negative cable" run (along with a connection to a ground rod, then back, eventually to the battery negative bus terminal), I don't think it will be a big issue... As Windsun warned, you just need to monitor your electrical connections to the tower and the ground/return path--If you get a "poor" connection somewhere, the DC current could cause rapid corrosion on the tower/re-bar/mounts (or even in your metal in ground water pipes--if you have any).

    So--Another question, besides asking which solar charge controller you are planning on using, what Imp/Vmp/Vmp-array of array are you planning on installing?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    The answer to your question is. . . Don't know yet

    I think I am going to just rely on the grounding at the inverters for the earth, except for the hardware grounding at the panels.

    Running a separate supply to the utility station is out of the question. I have 3/0 stuffed in pipe laced through the house to get to the station. I will have to consolidate at the roof in my attick. The good thing is it's all mechanical lugs and i am using dielectric silicone grease on the connections. Nothing will be corroding in there. And they are easy to access and inspect. I am a good one for preventitive eyeballing every system in the house.

    As far as the controller is concerned, maybe this will tell you about my mistake. Or is it?
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    Attachment not found.

    Attachment not found.


    This is what I look like in my 150 year old house. Still under construction. I have to finish the metering and have a few odds and ends on the battery side. Need to finish the grounding too on the Battery side. They're separated because of lack of room
  • BB.BB. Posts: 25,139Super Moderators admin
    Re: Solar panel grounding

    In general, it would be better to use a "real" solar charge controller--And if you have a fairly large array and/or longer wiring distances, a MPPT type charge controller.

    Also, if you have "non standard" Vmp array (I.e., Vmp-array above or below ~35-37 volts), you will probably need a MPPT solar charge controller too for optimum power transfer from the array to the battery bank.

    For example, if you have a 24 volt battery bank (~29 volts charging) and a Vmp-array ~96 VDC nominal--29/96=1/3.3 reduction in current. Also, since the voltage is ~3.3 times higher, that allows you to use around 1/4 or smaller gauge of wire from the array to the battery bank.

    For connection from the MPPT solar charge controller to battery bank--You need a fairly short/heavy run to avoid having a lot of voltage drop.

    If you use a MPPT (or PWM) solar charge controller), you would set the Dump Controller's dump voltage > than the solar charge controller. This would allow the solar panels + charge controller to more accurately recharge your battery bank.

    And just use the Dump Controller when you have lots of wind.

    If you plan on direct connect of solar array to battery bank--Then just do that (with appropriate fusing/breakers) through the heavy cable you already have laid out. We don't really recommend dump controllers for solar--But they will work.

    Anyway, what are the solar panels you are thinking of using, and how many? That will define much of your system requirements.

    Lastly, I agree that there is no way to rate the dump controller at 440 Amps. Using ABYC Marine Standards, 440 Amps would still require 4/O cable... (NEC would even require heavier cable--Roughly 750 kcil). 3 AWG is even pushing it at ~175 amps (ABYC).

    MPPT solar charge controllers ain't cheap... But when you take wiring issues into account--the are usually a pretty good solution.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    3 AWG? No 3/0 Different gauge. 3/0 is 550 amps as i recall. The copper core is almost the size of a nickle. I went to that because the voltage drop is considerably less on longer runs. My 3/0 is 90 feet. I did cheat by using 2/0 to the inverters, rated to 440 Amps. I am feeding the dump controller in and out with 3/0. Then feeding 2 battery banks with 2/0 each. Both are fused at 250 amps. Close but no big overkill.

    These dump controllers are made to dump on voltage. I reworked this one to do that and handle the 440 Amps. I have it set to dump at 26.5 VDC. The inverters are responsive enough to take the solar input and way larger than I am going to be able to produce. So on a windy/sunny day like today, I may see an occasional dump. I've been looking at these charge controllers and realized the Outbacks are set to kick in at 25.8 VDC. Drop at 25. From what I can tell, the inverters are very responsive. I watch the amp meter and the DC Voltage and they seem to move with each other

    The panels I am leaning for is Hyundai 248's. I can fit 6 of them in the 9 X 11 spot I have. And 2 more on an adjacent roof. Rated at 24VDC 32V open. 18%. Going to make my own mounting. I can do it for less than 300 vs 1500 for all that. Pays to have all the tools and access to lots of aluminum extrusions.

    Going against some of the grain here and there, but it's simple and I'm not making some patent owner rich. LOL The only part I have regrets about are the inverters. Well, let's say partial regrets. The 4300 bucks for those hurt! But they are the best and warrantied for 10 years.

    Eventually I am expecting to have about 5000 watts of Solar and 3000 watts of wind on a postage stamp.
  • BB.BB. Posts: 25,139Super Moderators admin
    Re: Solar panel grounding

    Sorry--I miss-heard your video and thought you said 3 AWG...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PolaracoPolaraco Posts: 102Solar Expert ✭✭✭✭
    Re: Solar panel grounding

    POST JUMPER! :D ;)

    That's why I was questioning the way I did. I said 3/0 a few posts back. I was wondering where you got #3 from. No Problem.

    Now you should be able to run my system. You know about as much about it as I do. LOL Except where the blood and cheaters are.
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