New install questions

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  • VicVic Solar Expert Posts: 3,082 ✭✭✭✭
    Re: New install questions

    And, gww, this may have been answered already in this data-rich Thread,

    But, the MNPV12 Combiner shows a Segmented BusBar, so you should be able to easily use two CCs, each with its own PV output Buss. Believe that this Combiner box now ships with a second PV Negative Buss, like the one shown at the left of the pic in the Link. In the case of you needing this second PV Neg Buss, (which should mount where the Ground Buss is pictured), you would need a single space Ground Lug. MN is a heads-up company, so the single space ground lug is probably included.

    EDIT: here is a pic from the MN site of an MNPV12 shown with segmented PV + Buss, and both PV Neg busses and a Ground Buss:
    http://www.midnitesolar.com/productPhoto.php?product_ID=144&productCatName=PV Combiners&productCat_ID=9&sortOrder=9

    It does not hurt to wire each array's PV Neg wires to its own Neg Buss -- this adds fliexibility, as some PV Gournd Fualt detectors need it, IIRC. 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.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Vic
    Thank you for your info. I should be getting it any day. The only thing I forgot was a hydro meter. I was trying to save on shipping by getting what I thought I needed all at once.

    Ggunn
    Thanks, I was sure glad to find the online caculator also.

    Chris
    Yea, I was the one you spent three days before I even got the concept of what you were doing. You were great. You probly should feel sorry for these guys, expecialy bill as I am sure he is getting writers clamp just trying to get through to me. You were great though.

    Bill
    I spent a little time drawing a basic paint diagram of how I was talking of wiring my system but then couldn't get it to load so I gave up. I did read all your links that you posted for me. Just made me feel like a bigger idiot. You posted.
    Note, the above are discussions, not a do A, B, and C--and you will be "safe". There probably is no such thing with lightning. Several different techniques are discussed--and a few of those posters even have experience with lightning.

    I don't think I am doing well with the discussion part and need an A, B and C-- and I will be as safe as that will make me. I will get as close as I can and then quit worrying.

    The things that screw me up are;
    1. The outback drawing shows a ground at the pv and nothing from the combiner going to the house. A seperate ground goes from the batteries to the inverter to the ac main panel.
    2. The combiner wiring drawing goes; The combiner wiring ground shows from the pv to the combiner to the inverter to the main ac panel with no ground rod at the pvc. I believe this fits the new nec rule to the minimum.
    3. You seem to be saying that, above minimum, the pv should have a ground rod that goes through the system to the ac panel which ends up at the house ground rod. Am I getting the wrong ideal here and would the sequence be from the pv frames to the ground rod to the combiner to the house?

    I need it short and sweet cause there seem to be conflicts that I am having a hard time picking through.
    If it works reasonably well I don't worry to much after it is done. I don't want to do something that is so blantantly stupid that someone can call me on it and be right.

    If I add a ground rod at the pv do I have to worry about the impedance matching the house rod?

    I know you like the ground rod at the panels I just need to know the two points it hooks at to keep it a safe thing and not a bigger hazard.

    I can't believe I can read that many post and can still be confused. I am sorry, can you try one more time, PLEASE?
    Thanks
    gww

    should I run the ground from the pv frames to the combiner box to the ground rod at the pv then strait to the house ground rod and have the inverter side connected to the ac panel ground buss bar? This means that the pv gound rod takes a different rout to the house ground bar then the inverter and batteries? have I got it yet?
  • BB.BB. Super Moderators, Administrators Posts: 31,625 admin
    Re: New install questions
    gww1 wrote: »
    Bill
    I spent a little time drawing a basic paint diagram of how I was talking of wiring my system but then couldn't get it to load so I gave up. I did read all your links that you posted for me. Just made me feel like a bigger idiot. You posted.
    ...
    I don't think I am doing well with the discussion part and need an A, B and C-- and I will be as safe as that will make me. I will get as close as I can and then quit worrying.

    Grounding is a pretty complex subject and subject to various theories on how best to implement lightning and safety measures. Doing this in writing, remotely, and with somebody who knows just enough to get into deep trouble...

    Remember, I am neither a licensed electrician, an expert in lightning control, or at your site--Best I can do is, hopefully, give you some information and links to follow up on and/or get some local/expert help. If you know any HAMs (amateur radio folks)--You can get some good help from them.
    The things that screw me up are;
    1. The outback drawing shows a ground at the pv and nothing from the combiner going to the house. A separate ground goes from the batteries to the inverter to the ac main panel.

    A very good lightning ground system would be to ground the array and mounting to a local ground rod.

    Ideally, run the lightning ground among the framework and the mounting directly to the ground rod. I would not run the lightning ground from the array through the combiner box to ground (that is "bringing" the lightning energy very close to your DC connection lugs--There is no reason, in my mind, for doing that.

    Just run a separate 6 awg ground from the local rod to the combiner box ground connection.

    The link you provided:

    http://lib.store.yahoo.net/lib/wind-sun/PVcombiners-explained.pdf

    Shows the array frame grounds going to the safety ground bus inside the combiner box... I would (as I said earlier) run the safety ground wires directly the array ground rod. I do not see a good reason to bring the lighting induced current anywhere close to the DC power connections if I did not have to do that.

    That would be the "end" of the array lightning ground discussion.

    My suggestion of running a 6 awg wire from the array ground rod back to the house main ground rod--That is for providing an AC/DC electrical bond between the Array and the Home Power Station grounds. It is possible to energize structures so that you have different voltage levels 100' apart. I personally like to bond the out structures with the "same ground" as the source of the power (i.e., home power--whether AC or DC, locally generated or power lines from a utility). This will not help with lightning, but can help reduce the chance of shock between a power tool using power from your home around the solar array structure (i.e., a three wire power metal electrical drill working on the metal framework with a "different" ground potential).

    It is not a common problem--But there can be voltage gradients in the earth. For example, electrical power pylons can have leakage current (dirty insulator, etc.) that can "energize the local earth". There have been cases where cattle have been killed by standing near a pylon (for humans, our feet are close together and power goes up one leg and down the other. For cattle, their legs are far apart and current can flow up the front legs, through the heart and back down the rear legs and kill them).

    If you do not, for example, run AC power from your home to the solar array structure (shed near by, yard lights mounted to frame work, an "extra AC outlet" for back yard lighting/music/etc... Then the linking of the remote and main ground is probably not necessary (I am not doing this based on code, just based on safety concerns that I have).
    2. The combiner wiring drawing goes; The combiner wiring ground shows from the pv to the combiner to the inverter to the main ac panel with no ground rod at the pvc. I believe this fits the new nec rule to the minimum.

    The Midnite document (above link) talks about grounding as "Safety Ground"... Basically just running wires from outlets/branch circuits in the home to a common ground bus bar, then back to the main panel/earth ground rod. That is perfectly good for a "safety ground".

    With lightning, it is "RF Energy" (Radio Frequency Energy). The energy does not follow "copper wire"--It also is affected by the inductance and capacitance of the cabling (which is frequency dependent).

    More or less, while 60 Hz energy follows the wiring through the home wiring, Lightning energy moves to the "outside" of the structure (magnetic repulsion pushes the current away from the center--this happens with 60 Hz AC current too--But the effect is less much less than an inch--skin effect).

    When grounding against lightning strikes, say you have two cables going to lightning rods on the roof. The two cables should be at opposite sides/corners of the home/grain silo/etc. (as far apart as possible). That is how lightning wants to flow. Running 6 awg cable into a metal box--Not real likely to follow just that route.
    3. You seem to be saying that, above minimum, the pv should have a ground rod that goes through the system to the ac panel which ends up at the house ground rod. Am I getting the wrong ideal here and would the sequence be from the pv frames to the ground rod to the combiner to the house?

    NO. I am not saying that.

    Solar Panel Frames->grounding cable->local ground rod
    AC Main Panel Earth/Safety Bond->another grounding cable->main panel grounding rod
    AC Main Panel Neutral Wire (north America)->Earth/Safety Bond bus block in main panel (*see note)
    Water Pipes/gas pipes in home/etc.->yet another grounding cable->main panel grounding rod
    DC Ground Bus (negative Battery post, etc.)->and yet another grnd cable->main panel grounding rod
    Solar panel local grnd rod -> XYZ feet of 6 awg cable -> main panel grnd rod (optional)
    *NOTE: Most (most/all?) MSW Inverters will create an internal short circuit if the Battery Bus is grounded to building Safety Ground (i.e., ground rod/ground bus) and the "White Wire" of the MSW Inverter output is "bonded" to the same Safety Ground (as seen in Main Panels where White/Neutral and Green Wire safety grounds are in the same box). If one output wire of the MSW inverter is tied to Earth Ground along with Battery Bank to safety ground bond--It will smoke the MSW Inverter.

    Most (some/almost all) TSW inverters can have one of their outputs tied to Earth/Battery safety ground at the option of the owner without problem.
    I need it short and sweet cause there seem to be conflicts that I am having a hard time picking through.

    So:
    • Solar Panel Frames direct to array ground rod. (lightning control)
    • Combiner box earth/safety Ground to array ground rod. (lightning control). Do not connect the solar array negative wiring to the safety ground bus--Just to the insulated bus bar).
    • Battery Bank Negative Lead to building ground rod (safety ground for DC and AC shorts, some lightning suppression too)
    • OPTIONAL: 6 awg cable from Array Ground Rod to Building Ground Rod
    • IF YOU HAVE GRID POWER: Your AC Neutral will be tied to Earth/Safety Ground in the Main Panel.
    • IF YOU DO NOT HAVE GRID POWER AND A MSW INVERTER: You will want to "float" AC White Wire--Do not attach to Safety Ground.
    If it works reasonably well I don't worry to much after it is done. I don't want to do something that is so blatantly stupid that someone can call me on it and be right.

    If this was an RV (for example) where you sometimes have power from an RV park, and a local inverter, and a local AC generator--Then we need to talk about Neutral bonding/grounding some more.
    If I add a ground rod at the pv do I have to worry about the impedance matching the house rod?

    Not that I can think of--There is a ground rod test (special equipment)--But I have never been involved in this--That would be your electrician that would determine if your ground rod is "good enough" (dry earth, frozen earth, rocky ground, etc. can be very difficult to get a "functional ground" connection between rod and earth).
    I know you like the ground rod at the panels I just need to know the two points it hooks at to keep it a safe thing and not a bigger hazard.

    I believe that the usual install is to run an "S" of cable through each panel ground clamp (and major structure connection) directly to the array ground rod (NEC requires a single unbroken wire--You are not supposed to splice ground wires). I would believe it is OK to break a run into two or more runs of copper (i.e., 4 panel frames to ground rod, another 4 panel frames to ground rod, etc. if that works better).
    I can't believe I can read that many post and can still be confused. I am sorry, can you try one more time, PLEASE?
    Thanks
    gww

    And anyone with more experience than I--Please jump in... I am a bit out of my depth here.
    Should I run the ground from the pv frames to the combiner box to the ground rod at the pv then strait to the house ground rod...

    and have the inverter side connected to the ac panel ground buss bar? This means that the pv ground rod takes a different route to the house ground bar then the inverter and batteries? have I got it yet?[/QUOTE]

    Lightning Ground Cable should run directly from the frames, down the side of the structure/outside of home, etc. to the closest earth, then drive your ground rod there and connect the ground cable. No extra jogging this way or that way if you can avoid it. Lightning current should go to earth the shortest path possible... Running wire 40' along the side of the house to a different patch of earth won't cut it. The Lightning will want to leave the wire and seek ground through another path (wire/conduit in wall, etc.).

    Personally, I would run a separate ground wire from the combiner box to the array ground rod (or house ground rod, or even a ground rod driven under the combiner box--depends on where the combiner box is installed). Remember, lightning ground should be short and straight down to earth. If combiner box is on south wall and AC panel ground is on the north wall--Drive a ground rod on the south wall under the combiner box (technically, combiner box on side of your home, I think you would have to run a ground wire from the AC main panel ground rod to the new combiner box ground rod--The combiner ground rod takes care of lightning current, the 6 awg back to main panel ground rod takes care of AC and DC currents in the event of a short circuit).
    ...and have the inverter side connected to the ac panel ground buss bar? This means that the pv ground rod takes a different route to the house ground bar then the inverter and batteries? have I got it yet?

    You lost me here...

    We have not really discussed inverter grounding yet (other than the MSW inverter output neutral bonding warning above).

    Before we talk about this--Let us make sure you agree/understand with what I have said so far.

    TSW/MSW Inverter/AC Mains/Generator neutral bonding is a whole 'nother set of worms.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: New install questions
    BB. wrote: »
    Grounding is a pretty complex subject and subject to various theories on how best to implement lightning and safety measures. Doing this in writing, remotely, and with somebody who knows just enough to get into deep trouble...
    (NEC requires a single unbroken wire--You are not supposed to splice ground wires)
    -Bill

    More accurately, any splice used in a grounding wire (not the individual ground wires in branch circuits, but the primary wire leading to the grounding electrode) must be "irreversible", so that it can become disconnected accidentally or inadvertently. One example of an irreversible splice is a suitably rated hydraulically crimped coupling.
    SMA SB 3000, old BP panels.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: New install questions
    gww1 wrote: »

    Ggunn
    Thanks, I was sure glad to find the online caculator also.

    The online calculator is more than likely just an Excel spreadsheet with a lookup table referencing data from those same tables in the NEC. I prefer to look up the values myself rather than trust someone's programming, but whatever floats yer boat.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    ggun
    Your point is taken. I didn't know there was a chart in the nec guide. I was still glade that I found the caculator on line because no one had mentioned the info you provided and as you can see, my math wasn't getting it done. It was nice when I punched my wires in that it showed 1 and one half inch rather then the 4 plus inches

    inetdog
    Thanks

    Bill
    I finaly understand I believe. You wiring sounds like the outback digram I took a picture of and posted on the other site. During This posting I have got better at transfering info into my post. So here is the link to the outback wiring diagram that I had used with my questions.

    http://www.energymatters.com.au/images/outback/ps2ac-dcsystem48vGT.pdf

    I only see one differance to the post you wrote and this diagram. In the diagram the combiner is not hooked to a ground rod at all. The panels are hooked to the pv ground. Where the wires from the combiner end up being connected there is a ground to the house system. There is no ground on or from the combiner box its self. You say go from the combiner box to the pv ground rod. Would both, one (hooked to the pv ground rod) or the other (hooked to nothing) be basically alright? Your thoughts? I do believe I understand your A, B and C-- directions. I am no longer questioning what you mean (my problim, not yours). I am just curious of your thoughts on this.

    I know why you have 15000 plus post. I can't thank you enough. Guys like me can't make it with out guys like you. I was not getting the specialized help I needed on the otherpower forum. On different subjects I have a few times got amazing help from the otherpower forum and it was a member there that sent me to you. I hope I can help others on items I might know. They won't get much cause I don't know much. This is a thank you note to all you guys that answered and try to help. I for one apretiate it. I would like your comments on the last grounding portion but believe I have actually put the system together to the point that I needed when I started this post. I won't say new questions won't come up but I am smarter then when I started. I still need to figure out where to get things like comprestion grounding fixtures, whats the cheepest and safest way to mount my panels, towers for wind and other connectors. Long ways to go and lots of money to spend. Updates when I am done.
    Thanks
    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    For the heck of it I thought I would show you some of what I have been doing till I get back home for good.
    Attachment not found.

    About a third of the solar that I have built. I was playing with them with an illeagle gti.
    Attachment not found.

    A twelve volt charge controller and 500 watt dumpload I made for a different turbine I made.
    Attachment not found.

    Good, bad or ugly, This is what I have been doing in my spare bedroom and on my patio.
    cheers
    gww
  • BB.BB. Super Moderators, Administrators Posts: 31,625 admin
    Re: New install questions
    gww1 wrote: »
    ...when I punched my wires in that it showed 1 and one half inch rather then the 4 plus inches

    GWW, If you are trenching to the array--I would go large diameter and even lay down one or two extra conduits--If you want to add anything later--it will be much easier.
    http://www.energymatters.com.au/images/outback/ps2ac-dcsystem48vGT.pdf

    I only see one difference to the post you wrote and this diagram. In the diagram the combiner is not hooked to a ground rod at all.

    The thing to do is think about what can happen. For example, if a + wire comes loose in your metal combiner box, you want the box to be at the same voltage (i.e., local ground or zero volts) as the array, racking, etc... You don't want the box to be "hot" and somebody get electricuted if they touch the box and grab the mounting or step in a puddle.

    For electrical--Normally electrical enclosures need a "green wire" (or safety ground) tied inside the box... They do not count on mounting hardware for the "safety ground" connection... That is why you need a green wire from the combiner box to the local/array ground rod.
    The panels are hooked to the pv ground.

    Just to be very clear--You have a positive and negative set of wires from the array, and a metal frame. What does "PV Ground" mean to you?
    1. There is the Solar array ground rod--Which connects to the Panel Frames (and mounting).
    2. There is the DC Ground at the Battery bank which (most people) connects to from the Main home ground rod to the battery bank negative bus connection.

    So--there are at least two PV Grounds here we are discussing.

    The Array Grounding is only the Solar Panel Frames that is grounded to the solar array ground rod (local ground rod in your case).
    Where the wires from the combiner end up being connected there is a ground to the house system.

    Which wires? Red (+), Black (Negative) or Green/Bare (Ground)?

    The red/black wires run back to the charge controller... There is no "ground connection" at this point.

    The green/bare wire runs to the local/solar array ground rod (panel frames and electrical boxes).
    There is no ground on or from the combiner box its self.

    Yes there is... The link you provided showed a "Ground Bus Bar" that is also bolted to the metal box (no insulation--connected electrically).

    If there was no ground bus--There still will be a threaded hole with a "Ground Symbol" where you are expected to connect the green/bare wire to.
    You say go from the combiner box to the pv ground rod. Would both, one (hooked to the pv ground rod) or the other (hooked to nothing) be basically alright?

    Hooked to "nothing" is not OK. A floating metal box with internal electrical connections can become "hot" and electrocute somebody if it is really floating (obviously, a metal box, connected to a metal rack, with metal screws is connected electrically--But it is not, generally, good enough for NEC).

    If the metal box was attached to the wood siding of the house/barn/shed--Then it would be "floating" and could be an electrical shock hazard (anything over ~12-60 volts is "unsafe" for most codes).

    Your thoughts? I do believe I understand your A, B and C-- directions. I am no longer questioning what you mean (my problem, not yours). I am just curious of your thoughts on this.

    Just be very clear about what wires/connections/etc. and where you are talking about (remote array, in the home, AC or DC side, etc.).

    I am sorry it is so complex--and doing this via typing is making it more difficult--I am sure--To understand.
    I know why you have 15000 plus post. I can't thank you enough. Guys like me can't make it with out guys like you. I was not getting the specialized help I needed on the otherpower forum. On different subjects I have a few times got amazing help from the otherpower forum and it was a member there that sent me to you. I hope I can help others on items I might know.

    You are very welcome--Not having a "life" allows for more time to type too. :roll:

    We point people to OtherPower forum all the time too--For wind and other power based DIY type projects.
    They won't get much cause I don't know much. This is a thank you note to all you guys that answered and try to help. I for one appreciate it.

    We all learn, and if you document (write/photos) of your project and hang around a bit--You will be helping others too.
    I would like your comments on the last grounding portion but believe I have actually put the system together to the point that I needed when I started this post. I won't say new questions won't come up but I am smarter then when I started. I still need to figure out where to get things like compression grounding fixtures, whats the cheapest and safest way to mount my panels, towers for wind and other connectors. Long ways to go and lots of money to spend. Updates when I am done.
    Thanks
    gww

    You are very welcome.

    Do the paper designs first--That will save you the most money (and you can do A/B/C designs and see what works best for you).

    Avoid doing too much on the "cheap"... You want rugged/reliable power==and you don't want to burn down your home in the process.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,625 admin
    Re: New install questions

    I will add a link to this thread:

    Panel Fire Question

    This was actually a contractor installed/city inspected system. Even if you try to do things "right"--You can still get blindsided.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    GWW, If you are trenching to the array--I would go large diameter and even lay down one or two extra conduits--If you want to add anything later--it will be much easier.

    Agreed.
    http://www.energymatters.com.au/imag...ystem48vGT.pdf

    I only see one difference to the post you wrote and this diagram. In the diagram the combiner is not hooked to a ground rod at all.
    The thing to do is think about what can happen. For example, if a + wire comes loose in your metal combiner box, you want the box to be at the same voltage (i.e., local ground or zero volts) as the array, racking, etc... You don't want the box to be "hot" and somebody get electricuted if they touch the box and grab the mounting or step in a puddle.

    For electrical--Normally electrical enclosures need a "green wire" (or safety ground) tied inside the box... They do not count on mounting hardware for the "safety ground" connection... That is why you need a green wire from the combiner box to the local/array ground rod.[/
    QUOTE]

    I was only pointing out that the outback wiring diagram clearly points out all green ground wires and where they go and there is clearly no ground from the combiner box. I do understand your thoughts on the matter now.
    The panels are hooked to the pv ground.
    Just to be very clear--You have a positive and negative set of wires from the array, and a metal frame. What does "PV Ground" mean to you?


    1.There is the Solar array ground rod--Which connects to the Panel Frames (and mounting).

    Poor sentence on my part. Your sentance labled 1. is what I thought I was typing.
    Where the wires from the combiner end up being connected there is a ground to the house system.
    Which wires? Red (+), Black (Negative) or Green/Bare (Ground)?

    The red/black wires run back to the charge controller... There is no "ground connection" at this point

    On the outback diagram the red and black wires go to the dc breaker box and then to the charge controllers. The dc breaker box is grounded through the mounting plate with the ac house ground.

    In the diagram there is no ground coming with the red and black wires from the combiner box to the dc breaker box.
    There is no ground on or from the combiner box its self.
    Yes there is... The link you provided showed a "Ground Bus Bar" that is also bolted to the metal box (no insulation--connected electrically).

    If there was no ground bus--There still will be a threaded hole with a "Ground Symbol" where you are expected to connect the green/bare wire to.

    We are mixing wiring diagrams. The wiring diagram that I posted for the combiner box showed the pv frames grounded to the combiner box then running to the house ground with no local ground at the pv location. Through decussion we have discarded that diagram and elected to put a local ground rod at the pv location. The outback digram has a local ground wire but no ground what so ever to or from the combiner box.

    The only reason I ask the nothing at the combiner box was to try and figure out why outback would have a local pv ground rod with the frames of the panels hooked to it but had the combiner box with no grounds going to or from it. I thought that maby because they were hooking the black and red wires to a grounded dc breaker box that they didnt want to hook the combiner box to the local pv ground rod because they didn't want the black and red wire to transfer the energy from the local ground rod to the house electrical system. I'm am mostly trying to figure outbacks reasoning for this in case it was ligitamate.

    I don't mind hooking the metel combiner box to the local pv ground rod as I see it being a lot cheeper then running ground wire from the combiner box 200' to the house.

    Money? I got 7600 in my stuff already. I don't want to skimp but don't mind finding cheaper ways of doing things if I can make it work.
    Thanks
    gww
  • H2SO4_guyH2SO4_guy Solar Expert Posts: 213 ✭✭✭
    Re: New install questions

    Bills quote below:

    [*]Combiner box earth/safety Ground to array ground rod. (lightning control). Do not connect the solar array negative wiring to the safety ground bus--Just to the insulated bus bar).

    If you do this the negative from array will be connected to the - terminal of the charge controller which is connected in parallel to the battery - terminal, which is connected to safety ground at the main ground rod. What is the difference in connecting the - of the array at the combiner box to safety ground vs at the charge controller?

    Skip
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
  • BB.BB. Super Moderators, Administrators Posts: 31,625 admin
    Re: New install questions

    There can be a few issues...
    • Having a ground rod "remote" from the main power installation... If you have a strike nearby--You can have hundreds to thousands of volts difference between the panel ground rod and the local ground at the building (main ground rod if you have Grid power, local water pipes etc.).
    • You want only one safety ground connection--You don't want one at the solar array and a second at the building (again, lighting strike causes voltage gradient). I have seen > 60 VAC (leakage current from multi-horse power salt water circulation pumps?) between two ground rods driven a 100 feet apart in a large marine park--So, what is "ground at the array" is not necessarily "ground" at the battery bank/building.
    • I like short/heavy ware from the main battery - terminal (bus common) so that you have very low resistance / high current capacity in case there is a short circuit (DC circuits may have 200 amp or larger fuses--You don't want that sort of current going down the solar ground wire to the remote ground point (not that you could drive that much DC current through a ground rod into earth). Lightning does not like to travel down cable very far (a few 10's of feet near earth). The impedance (inductance) of the (potentially) long wire run will be "useless" dumping lightning energy to ground.
    • If you have any other grounding requirements (like a generator, AC ground for main panel, etc.), you don't want to run the grounds from those out to the solar array ground rod (single point grounding).
    • If you have to pull your solar charge controller for service--You have now disconnected your battery bank's safety ground (which ran through the units DC Return wiring)... Normally, that is not allowed by NEC (you are not allowed to have a safety ground "lifted" as part of normal service--The safety ground connections have to have their own mounting points separate from other bolts to open a unit up for service or if you pull the device out of service).
    • At least one solar charge controller measures the array current though the DC negative power lead--You could get ground noise/leakage current which would confuse the MPPT function.

    Those are the reason I would not do it... In theory, yes you could ground the DC Return at the solar panel's negative lead in the combiner box). and it would probably function OK in many cases.

    In practice, it is usually not a good idea unless you have very specific reasons for doing it.

    Normally, in a lighting prone area, you might want to use a lightning/surge suppressor between solar panel's power leads and local earth ground.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    This is what I come up with as a safe ground based on the discussion in this thread.

    Attachment not found.

    If you follow my green lines, will this work?
    Thanks
    gww
  • BB.BB. Super Moderators, Administrators Posts: 31,625 admin
    Re: New install questions

    The green wire to combiner box to ground rod ONLY CONNECTS TO COMBINER BOX SHEET METAL. Not to any black/read solar array wiring.

    How are you planning on handling the green wire from the battery bank through the DC panel?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    I haven't got the outback manual here but I believe the inverter/dc panel/ac panel are all grounded to the mounting plate. If I remember correctly a ground is run from the negative battery post to the dc panel or inverter. I can't remember exactly but have printed the installation manual to go by.

    I did understand that the pv power wires would not be attached to a ground, just the metal box.

    Thanks
    gww

    PS The outback ground is connected by your half amp breaker in the dc panel. I remember seeing this and I believe this is one of your pet peeves. From the factory.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: New install questions

    If you are following the NEC DCGFI regs the negative battery post is not connected to ground.

    Just thought that should be mentioned. Doesn't mean I agree with it. ;)
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Cariboohoot
    I got the inverter used. I cant remember if it is a 2005 or 2007 model but the manual I printed off line seems to match it. It is not in front of me but it seems I remember something coming from the battery. I have read so much that I could be getting mixed up with something else.
    gww
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: New install questions
    gww1 wrote: »
    If you follow my green lines, will this work?

    There should be a green line accompanying the red & black on that 200 ft run.
    Also, the sub panel should be connected to the main panel. The box that your inverter is mounted to can be a main panel, in which case the "main panel" in your diagram is really just another sub panel.

    Also, I would like to see the 200 ft run enter the house right near the house's ground rod.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: New install questions

    Regs have been changed since then. But if you don't have any of the DC GFCI stuff from Outback or MidNite it doesn't matter. Probably no inspector would catch it either.

    But yes, in the "old days" negative battery was bonded to ground, as was ESG wiring.

    Another NEC issue is the requirement that the frame/mount ground comes into the house with the other wires and follows the point-to-point path to the main grounding rod. Something else some of us disagree with.

    If this stuff were simple we could write it up in two paragraphs and make a "sticky". :p
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Cari....
    One of the reasons I decided not to grid tie even though that would make more finacial sence. I also won't be inspected but would like it to be safe and to have Things I can justify if I ever had a insurance misshap that may not even have anything to do with the system.
    Thanks
    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Vtmaps
    There should be a green line accompanying the red & black on that 200 ft run.
    Also, the sub panel should be connected to the main panel. The box that your inverter is mounted to can be a main panel, in which case the "main panel" in your diagram is really just another sub panel.

    I totally missed your post. The 200' run was the only reason I tried to draw it out. The last part of this thread was bill trying to get me to understand the way to run the ground. I had a couple wiring diagrams that showed different avenues of grounding and wasn't getting what bill was saying. I did think in the end we decided that it didn't make sense to run the pv ground in a way that would allow problems to be transfered into the house wiring.

    Also, I would like to see the 200 ft run enter the house right near the house's ground rod.

    --vtMaps

    The picture I drew was not totally represenative of the actual set up. I am actually running the house ac to the inverter in my shed from a ac panel in my shed. Then from the inverter sub panel to a sub panel in the house that I will transfer dedicated loads to. I see no way to come in by the house ground rod.
    Cari...
    Another NEC issue is the requirement that the frame/mount ground comes into the house with the other wires and follows the point-to-point path to the main grounding rod. Something else some of us disagree with.

    The whole reason I drew the picture was to verrify that not bringing the pv ground into the house would be the safest rout all things considered. I will not be inspected. It was the discussion of the disagreement that we decided not bringing the pv gound into the house was best. I just had a really hard time understanding what was being said and put this out one more time to make sure. comments are welcome.
    Thanks
    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Cariboohoot
    But yes, in the "old days" negative battery was bonded to ground, as was ESG wiring.

    What is ESG wiring?

    Thanks
    gww
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: New install questions

    Electrical Safety Ground - old term that apparently no one younger than a dinosaur uses anymore. :blush:
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Cariboocoot

    I am soon to be 51. I don't know how old I have to be to reach dinosaur status but I move like I am in a tar pit some times. My only electrical background has to do with small remodel jobs and keeping up a few rental houses. Do it your selfers don't really run into real terms but just try to repeat what they can see is already done. Hopefully the first guy to touch it knew what he was doing.

    Thank you
    gww
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: New install questions
    gww1 wrote: »
    Hopefully the first guy to touch it knew what he was doing.

    Regrettably that is so often not the case! :cry:
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