Battery Grounding

I am getting conflicting stories about grounding the batteries, in a solar panel to battery to inverter, setup. Can anyone steer me to some info that defines what really needs to be done here? I have contacted two suppliers, who have not written back.

Thanks.
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Comments

  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Battery Grounding

    Electrical wise there is usually no difference. One of the major reasons for grounding them is lightning protection.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    Here's my take from John Wiles, the SEI PV Design Manual, and OutBack's latest MX60 manual:

    1) DC system common is usually bonded to ground at one point.
    2) If there's a GFI breaker, it's placed between system common and ground.
    3) Battery negative is connected directly to system commom is there's no shunt.
    4) if there's a shunt, then batteru negative only is connected to the battery side of the shunt, and system common is connected to the system side of the shunt.

    I hope I got that right...
    Jim / crewzer
  • BB.BB. Super Moderators, Administrators Posts: 29,246 admin
    Re: Battery Grounding

    Jim,

    Your GFI comment is not really clear (at least to me). The standard GFI breaker/outlet is an AC only device. It will not do anything with DC.

    Also, the GFI connectes to ground, and not "...it's placed between system common and ground". Normally, you would not want to switch/breaker any ground connections.

    A GFI will only work correctly with a ground bonded neutral system (US style). It has a small transformer wrapped around the neutral/hot leads going out of the outlet. Any AC current that goes out the hot, and does not return on the neutral is assumed to be a short to ground (possibly through a human body). Un-ground referenced AC circuits (such as an inverter)--a GFI will not trip as there is no current flow when the "hot lead" is grounded (as there is no neutral/ground connection with an inverter--unless one has been added).

    At around 5-15 mAmps of ground leakage current (or a bit more, don't know the exact spec.), it opens the switch/breaker.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • backroadbackroad Solar Expert Posts: 185 ✭✭
    Re: Battery Grounding

    I really hate to butt in with this, but yoou guyes teknikal nolege is good butt giving me a migrane.....:D:D
  • System2System2 Posts: 6,290 admin
    Re: Battery Grounding

    Thanks for the comments, guys. I am using a Midnite Solar Mini DC Breaker Box, including a shunt, as "crewzer" mentioned. The store were I bought the box, is just starting out in solar themselves. The man told me not to ground the batteries, so I have all components hooked up to system ground, except the main battery negative. This didn't feel proper, but now I believe I can go with my instincts and hook up the system side of the shunt.

    This forum also had a link, in one of the other sections of this forum, for NEC information that relates to my concerns. Thanks again, for helping out a newbie.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    Bill,

    You raise a good point, as I don’t this the DC GFI issue is well understood. In short, the NEC requires DC GFI protection for installations with roof-mounted arrays. The required breakers are standard equipment with the new Xantrex MPPT charge controller, and they’re optional with legacy controllers such as the MX60.

    A typical DC GFI installation includes a ganged two-pole circuit breaker. A circuit between the system common buss bar and the ground buss bar is run through the low-current breaker, and the PV array (+) circuit is run through the high-current breaker. If a ground fault occurs, the low current breaker is thrown, and it mechanically opens the high current breaker, thereby disconnecting the array as a power source.

    The latest MX60 manual has a schematic of all of this on page 13.

    I’m not sure how this is done with battery-less grid-interactive inverters like yours.

    HTH,
    Jim / crewzer

    P.S. My head hurts too, sometimes...
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    Solar Flare,

    The Mini DC breaker box and its instructions depict how to wire up your system to include the DC GFI. You should be OK if you follow this schematic but also remember to actually connect the box, inverter, charge controller, and PV array to a ground point.

    If you've elected to not use the DC GFI, then just complete the circuits as if the breakers aren't there.

    HTH,
    Jim / crewzer
  • BB.BB. Super Moderators, Administrators Posts: 29,246 admin
    Re: Battery Grounding

    Jim,

    Well, I learn something new every day... I stared at the circuit you posted to for 10 minutes, and--for the life of me--I can't figure out if this is a good thing or a bad thing (GFI for the panels)...

    GFI was, originally, intended for protection of users against shocks over ~10 mAmps or so, to prevent electrocution. A 1/2 amp breaker is way over the electrocution level--And DC shocks do not normally cause the Grip O' Death (where the person cannot release the object causing the shock) like AC does... So GFI is not needed for that reason...

    So the DC GFI is to prevent alternate current paths from the panel?--a good thing in most cases--but not typically something one would expect code to be written around. A 1/2 amp (or less) of leakage can still cause electrocution and electrolysis issues.

    On the other hand, what issues are there when the ground is broken by the breaker? There is some sort of resistor still in the ground circuit--but is the battery ground now floating (or grounded through the resistor?)?

    Generally, safety grounds are sized to pass the full available current. Here, the safety ground it only 1/2 amp of current? I don't think this GFI circuit would work right if the battery was also grounded to earth ground directly (in addition to the grounding in the MNDC box).

    How is lightening protection handled with this DC GFI setup?

    My head hurts too.

    -Bill:confused:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    Bill,

    I don't know the complete answer to your question. I'll probably start my research here: http://www.google.com/search?hl=en&q=ground+fault+PV+array&btnG=Google+Search

    HTH,
    Jim / crewzer


    Update: Here's the theory of operation statement from an old Trace site:

    Overview of Operation:
    When a ground fault is detected, the PVGFP disconnects the PV sub-arrays and switches the grounding systems from a low impedance, negative-ground bonding to high impedance bonding. This limits fault currents to a safe level, even when AC faults occur on the DC side of the system. For example, fault current will be held below 5 milliamps even for a 240VAC fault across the DC side of the system.

    And, this report looks pretty informative: http://www.nmsu.edu/~tdi/pdf-resources/pdf%20version%20divided%20PV:NEC/APPENDIX%20H.pdf
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    that's interesting. why do they expect 240vac let alone 110vac to be impressed upon the pvs and exactly how? this is highly unlikely to occur and if it did i would think one would know it by the fireworks that'll take place.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    My hypothesis is that there may be concern about overhead 120/240 lines entering a house near/at/above a roof's ridge line... :confused:

    Regards,
    Jim / crewzer
  • BB.BB. Super Moderators, Administrators Posts: 29,246 admin
    Re: Battery Grounding

    Hmmm... I have had arguments like this before with UL. From Jim's linked PDF:
    To understand how these GFPDs work, it must be understood that nearly all currently available inverters, both stand-alone and utility-interactive, employ a transformer that isolates the dc grounded circuit conductor (usually the negative) from the ac grounded circuit conductor (usually the neutral). With this transformer isolation, the dc side of a PV system may be considered similar to a separately derived system and, as such, must have a single dc bonding connection that connects the dc grounded circuit conductor to a common grounding point where the dc equipment-grounding conductors and the dc grounding electrode are connected. Like grounded ac systems, only a single dc bonding connection is allowed. If more than one bonding connection (a.k.a. bonding jumper) were allowed on either the ac side of the system or on the dc side of the system, unwanted currents would circulate in the equipment-grounding conductors and would violate NEC Section 250.6.
    A couple of decades ago, I had arguments with UL (about NEC interpretations) trying to ground large computer internal DC power systems at one point. And, we would get little nasties like smoked RS 232 cables sometimes, because of poor design, and other times because of an unintentional ground somewhere (typically between building AC ground, Isolated AC grounds, DC ground, and telephony/signal ground.

    With large systems (and buildings) and different grounding philosophies, one could not guarantee ground interoperability... (whomever decided that RS 232 was the cheap networking cable really caused huge problems).

    Anyway, back to the Ground Fault requirement... This requirement, as I understand, was only for pluggable equipment near water (sinks, pool, outside, etc.). There never was a GFI requirement for hardwired equipment like home lighting, central air, electric hot water heater, etc. (that I have seen).

    The phrase "...a separately derived system..." indicates that they are not worried about AC crossing over from the Inverter, the code is only concerned with power generated and distributed by the solar panels and their wiring to the inverters (and this is as it should be--the AC connected inverters should either be double insulated or included a grounded screen between AC and DC to prevent one level of failure causing hazardous conditions to the user). Once this is done, everything on the DC side of the inverter (solar panels in this case) is evaluated separately (in other words, the AC input on the Inverter is completely disregarded).

    So, now, we are left with solar panels and their wiring. Having a DC breaker (or fuse) on the ground connection. Looking at the schematic, all they are trying to do is prevent ground loops. But, nobody has ever tried to require even AC ground loops to be detected/break-ground in any distribution system I have seen. And, I have measured >60 VAC between AC system earth ground and a stake just driven into the ground a 100' away (and gotten shocked--was at an old salt water aquarium site for a research project).

    This does not really make the system any safer... breaking the ground in the event of a ground loop , is really just floating the safety to functional ground anyway. It would have been, at least as safe, if the ground was never made in the first place. Then, the power distribution would have had to have a double failure (short to "-" and a short to "+") for a "true failure" to occur.

    With the breaker open, a shorted "+" to earth is now "grounded" and the "-" which was earthed (through the breaker) is at -Vbatt (with full solar panel current still available to create earth short circuits)... And actually inverting the wiring potentials. Anyone working on this type of system would have to treat both sides as hot in any potential situation (normal operation and GFI tripped). Which then raises the issue of why require a DC ground in the first place if:
    A very high value resistance is usually built into the GFPD
    and this resistance bleeds off static electric charges and keeps the PV system loosely referenced to ground (but not solidly grounded) during ground-fault actions. The resistance is selected so that any fault currents still flowing are only a few milliamps—far too low to be a fire hazard.
    They are still trying to prevent a fire hazard--but the opening of the earth ground only opens one conduction path--there are still others potentially available. And if there were no DC ground requirement, there would have been no single point of failure ground loop path in the first place to cause a fire... (AC GFI's are to prevent shocks, not fires--DC GFI appears to be to prevent fires and not really to prevent shocks--at least not at the 1/2, 1, and 5 amps levels suggested).

    In normal wiring, if anyone ever measured more than a few volts on the 120 VAC Neutral (breakers tripped or not)--that would be a sure sign that there were problems in the installation of the house/office/etc. wiring.

    In fact, placing any breaker on a neutral (that I am aware of) is very much against code because of the issues caused (such as making anything connected to a neutral wire hot if tripped--such as standard Edison base light bulb socket outer "shell").

    In my 2 cents worth of opinion, they are creating more problems and issues than they are solving with this DC GFI. There is no reason to install a fuse/breaker in the DC ground, and many reasons not to do it. The DC side of the system should be grounded based on system requirements (lightening, Positive Earthing for some solar panels to prevent charge migration, etc.). But not for safety, that I can see.

    They are treating a solar panel completely different from any other DC power source. Battery systems, wind, and even AC powered power supplies with DC outputs should have this DC GFI scheme--if they were consistent with their methods and requirements (as well as requiring AC GFI for all AC hard wired distribution systems--not just outlets/plugs near water).

    End my ranting now--not even sure it makes sense to anyone else.

    -Bill

    PS: Regarding the issue of AC overhead lines causing an issue... Earth Grounded metal frames should help. Opening the safety ground simply energizes the DC Harness / Panels anyway.

    Plus, the grounding would need to be able with withstand 10,000 amps (normal limit for a pole mounted 120/240 VAC distribution transformer for homes). The normal earth ground wire would not be able to withstand that level of current long (would the fuse/breaker pop in a distribution transformer if an AC line hit a grounded solar panel?--don't know--but normally, everyone treats downed AC lines hot because of the variability of each situation).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Battery Grounding

    Bill, thank you for your rant/post. It does make sense to me for sure.
    Some of the things you mentioned, I've also found troubling, but figured it must be just me, because after all, these guys are the "experts".
    You have raised some very serious and frustrating issues that may take a generation to fix, as those in positions of power are unlikely to admit to their errors.
    Thanks again
    Wayne
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    very well put bill. i may have to look over the nec rules some, but i won't do that for another day or 2 so we may settle it here before i get to do more reading. anyway, anybody can give more protection against the falling of ac wiring onto their pvs. to be clear, the earth grounding of the frames is an absolute must. most pvs will send the power down 2 wires, one + and one - as we know. what i have in mind will work off of the + lead for sure. the arrangement i have in mind is a diode placed beyond the fuse/circuit breaker, when following the current from the pvs, going to ground. as some of you may already know this is used in protecting many electronic items by having a diode placed in a manor as to not allow the + to ground out through the diode as the polarity of the diode will be the opposite. the positive peaks of the ac may be able to flow depending on your pv voltage and the piv of the diode, but on the negative swings of the ac there will be a condition of a short circuit created.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    OK... I found some hopefully useful info on the NEC 690.5 requirement for GFP on PV arrays mounted on dwelling roofs. See the full Wiles and NEC link in this thread. Specifically, see pages 18-19, and all of Section H.

    HTH,
    Jim / crewzer
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    thanks jim, i'll look at it later.
  • BB.BB. Super Moderators, Administrators Posts: 29,246 admin
    Re: Battery Grounding

    Looking at the NEC file from Jim,
    Article 690.5 of the NEC requires a ground-fault detection, interruption, and array disconnect (GFPD) device for fire protection if the PV arrays are mounted on roofs of dwellings.
    ...
    Article 690.18 requires that a mechanism be provided to allow safe installation or servicing of portions of the array or the entire array. The term "disable" has several meanings, and the NEC is not clear on what is intended. The NEC Handbook does elaborate. “Disable” can be defined several ways:

    • Prevent the PV system from producing any output
    • Reduce the output voltage to zero
    • Reduce the output current to zero
    • Divide the array into non-hazardous segments

    The output could be measured either at the PV source terminals or at the load terminals.

    Fire fighters are reluctant to fight a fire in a high-voltage battery room because there is no way to turn off a battery bank unless the electrolyte can somehow be removed. In a similar manner, the only way a PV system can have zero output at the array terminals is by preventing light from illuminating the modules. The output voltage may be reduced to zero by shorting the PV module or array terminals. When this is done, short-circuit current will flow through the shorting conductor which, in a properly wired system, does no harm. The output current may be reduced to zero by disconnecting the PV array from the rest of the system. The PV disconnect switch would accomplish this action, but open-circuit voltages would still be present on the array wiring and in the disconnect box. In a large system, 100 amps of short-circuit current (with a shorted array) can be as difficult to handle as an open-circuit voltage of 600 volts.
    ...
    For a two-wire PV system over 50 volts (125% of open-circuit PV-output voltage), one dc current-carrying conductor shall be grounded. In a three-wire system, the neutral or center tap of the dc system shall be grounded [690.41].

    These requirements apply to both stand-alone and grid-tied systems. Such system grounding will enhance personnel safety and minimize the effects of lightning and other induced surges on equipment. In addition, the grounding of all PV systems (even 12-volt systems) will reduce radio frequency noise from dc-operated fluorescent lights and inverters.
    ...
    Some unlisted stand-alone inverter designs use the entire chassis as part of the negative circuit. Also, the same situation exists in certain radios—automobile and shortwave. These designs will not pass the current UL standards for consumer electrical equipment or PV systems and will probably require modification in the future since they do not provide electrical isolation between the exterior metal surfaces and the current carrying conductors. They also create the very real potential for multiple grounded-conductor connections to ground.
    I quoted various sections around the NEC link and it is obvious, they have forgotten why the NEC was written. It was to prevent fires and provide standardized safe wiring practices (first paragraph).

    And, they are stumped by the issue of solar panels that cannot be "turned off" (just like batteries).

    But, we may as well wring our hands about stored fuels too (can't "turn off" gasoline or diesel either--little bit of fuel+air+ignition source--and away it goes).

    Grounding vs ground loops in fixed installations have never been an issue before. In any house or building (not protected by an AC GFI near water), I can connect a 100 watt light to the neutral or the earth safety ground, and everything will work just fine.

    Why is this all of a sudden an issue with solar panels mounted on a building (but not mounted at the side of a building)? They are talking about fire prevention--everything is normally based on the current (and voltage) carrying capacity of the conductors (including the ground conductor).

    Then they get into the discussion about "...the grounding of all PV systems (even 12-volt systems) will reduce radio frequency noise from dc-operated fluorescent lights and inverters...". Sorry, a single safety ground is about useless for grounding RF noise. If you want to contain RF, you have multiple grounds around the entire chassis (or at least, multiple AC caps to ground).

    And then they get into the issue of DC appliances, such as car radios, and ground loops... Well, in vehicles, the chassis is the ground conductor (not a ground loop)...

    They have really gone of in the weeds on this one. There would not have been a ground loop problem with solar panels if they did not require a DC safety ground for an isolated solar panel. And, if they were really concerned about ground loops, they would have simply done the equivalent of floating both the + and - leads with a simple filament lamp to ground from each lead. If there are no shorts, both lamps glow dimly (each gets 1/2 the voltage drop, and there is no current flow through earth). If, there is a short to either of the + or - leads, then one light will glow brightly (full voltage) and the other will be out--with a small current (lamp current) through the safety ground.

    But, no, they want to use already listed and available components (like the ganged circuit breakers) to achieve their aims of preventing ground loops. Which was never an issue with AC mains...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Battery Grounding

    Bill, I wish you were running the Country, and no I'm not joking!
    Why has common sense vanished in modern North America?
    Have our schools "educated" it out of everyone?
    Shaking my head in dismay - -
    Wayne
  • BB.BB. Super Moderators, Administrators Posts: 29,246 admin
    Re: Battery Grounding

    Thank you very much Wayne. :blush:

    But I am still working on the power sharing arrangement with my wife (and two kids) at this time... :confused:

    I guess I should be clear here--I believe this is commentary on the NEC and how it affects solar systems. And how the NEC (when sections of the code are not clear) may be implemented.

    So--it is unclear to me if the comments were made with information from the authors of the NEC, or just trying to justify external discussions and implementation details by 3rd parties not involved with the NEC folks themselves.

    From what I have seen with UL (and other NRTL organizations), you sometimes have to work hard to educate them--but they will rarely force a product to be shipped with an obviously flawed designs (safety related issues) just to comply with the NEC--which is written for generic installations.

    And I ran into a couple issues in the NEC which were bad design practices (bordering on unsafe) with the NEC of 25+ years ago (I don't remember the exact issues--but IIRC, it was around DC power distribution systems and wiring connections, crimping, and requiring connections that did not use specialized tools--like Belcore rated terminal crimpers--for proper cable terminations in end use equipment). Last time I looked, it has gotten much better.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    in retrospect even with a gfci, a short on the roof with pvs could still cause a fire on the roof. when it does, those firemen are not going to walk on the pvs as they would normally walk on the roof and pop holes into it to gain access to the fire inside. that's not possible with pvs in place. what the heck will a gfci do for any of this? i could see if ac power lines are overhead, but in most cases the power lines run from the poles to the side of the building and not over the roof. they are creating imho a dinosaur as it is bigger than need be and is non existant in function, but who am i? yes, some do go to the roof, but usually near the edge and they certainly won't be over the top of pvs for any sane person, just to cover my butt on that.
    note: wiles did address my concern of running the ground through the house from the pvs as a means of lightning flowing into the house. i didn't totally tear it apart, but from what i remember it said something to the effect of running a ground wire down from the pvs and have a seperate wire to run through the house from the pvs as per their normal requirement. do i hear ground loop as well as lightning still being made to be able to get into the house? they also better start requiring 2 or more points on the pvs to be tested for grounding then. this gets worse as i think about it and i'm getting a headache picturing all the possible wrongs they're creating. they are starting to make it unsafer and more unecessarilly costly as well as contradicting their purpose imho. just for the record: my pvs are closer to the house main utility leadin than they would be up on top of my roof and mine don't need this gfci, but if i put them on the roof i do need the gfci and it's now farther from any possible ac source. they still are not in danger of contact with said wires where i have them as i wasn't born yesterday. ok, maybe the day before. hah i wish.:roll::D
    ps bill, i agree that you do post well and yes common sense is needed in this country as i wonder at times how some being that bad have lived as long as they have. real dangers to themselves and those around them.
  • System2System2 Posts: 6,290 admin
    Re: Battery Grounding

    John Wiles (New Mexico State, I think) has written some excellent articles on this subject. Check Homepower Mag. and IAEI.

    -auf-
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    i was addressing what wiles said and that i dissagree with the decision as i had emailed him about the concern i had for lightning travelling down that ground lead into the house. he did not eliminate that ground lead going into the house, but rather he just specified that it should travel to both a lead going into the house and a lead going to the ground rod outside that was not required before. this new requirement will mean 2 wires coming off of the pv frames and thus now no pvs are compliant due to only one ground hole point on the frame tested and 2 wires on one point is not approved. in my email to him i said it should not travel into the house at all, but only to the same ground rod that the ground from inside would go to as in a paralleled arrangement. his extra wire endangers the interior of the home needlessly and complicates the ground arrangement with no pvs being compliant and ground loops forming. dare i say i seem know more about this aspect of grounding than they seem to?
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Battery Grounding

    Hmmm... I suspect there is a way to satisfactorily address both the grounding and lightning protection issues.

    Check the attached articles from Wiles. It looks to me like one could have a heavy ground conductor from the PV array to a local ground rod to provide lightning protection and ground. You could also connect a separate ground conduction from the equipment in/on a house to this ground rod, or to another ground rod and then connect the two ground rods.

    See: http://www.nmsu.edu/~tdi/pdf-resources/CC102.pdf
    and: http://www.nmsu.edu/~tdi/pdf-resources/CC103.pdf

    Hope I got this right!
    Jim / crewzer
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    jim,
    i'm glad you put the links up here as the diagram on hp page 107 clearly shows what wiles conciders a good ground install. it shows a seperate ground rod without an underground tie for the pvs than that for the rest of the equipment and a ground wire leading into the home/building along with the dc leads. that's 2 things i object to as <1> the ground rod for the pvs should be underground linked to the other 2 rods shown. now in linking them underground a ground loop will be created as more than 1 path to the same ground is created by the <2> ground wire leading into the building and this same wire is what would allow a lightning discharge to follow a path into the building in its path to ground which there would now be one of 2 ways.
    what i propose to be better is a break in that ground wire before it is allowed to enter the building. this creates a paralleled path to the same single ground(due to all rods being electrically tied together underground) and eliminates the ground loop along with lightning being allowed to freely flow down that ground wire into the building in its quest to seek the ground. in spite of the wire to the ground rod dedicated to the pvs lightning is still free to travel into the building too when more than one path is allowed. as shown in the drawing if the combiner is outside the building then that's where the ground wire could stop, but that ground wire should not enter the building at all from outside. even their proposition of another ground rod untied with the rest of the ground rods underground goes against what they've always told us up until now and they allowed it to be at a different ground potential just to accomodate the ground wire coming into the building and thusly any lightning potentials as well. those using conduit would also need that break before entering the building, but that isn't difficult to do. did i confuse you or did you follow me on this?
  • System2System2 Posts: 6,290 admin
    Re: Battery Grounding

    Jim, you make perfect sense.
    I'm about to install 1000 watts of PV on my new wood shed and have been looking for grounding info that makes sense.
    Your info is what I've been looking for.
    Thanks.
    Wayne
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    wayne,
    if you fully understand it all then explain it to me as how you could dispell my concerns with this matter.
  • System2System2 Posts: 6,290 admin
    Re: Battery Grounding

    Sorry Niel, I didn't properly look at the top of your post. I saw "Jim" and without looking further, assumed it was he who posted. On second look, I see it was in fact YOU who made the post and ADDRESSED Jim. Sorry for the confusion man, it was you who made perfect sense to me. How easily one little slip can give something a completely different meaning. LOL
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    no problem, for i was hoping you could explain it to me as i really don't understand what the nec or wiles is doing in this case.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Battery Grounding

    Living in the lightning capital of the US, I never understood the concept of grounding the PV frames, thats a couple hundred square feet of lightning attraction that at best will vaporize the ground wire and at worst cause your home to burn to the ground.

    PV cells don't touch the frame, the Jbox or MC box doesn't touch the frame, there is no way a panel defect can energize the frame.

    One of the nice things about regulations, is that is ALWAYS upto the local inspectors to what is acceptable, regardless of what the NEC has written.

    In all my installations, with full written approval of the local inspectors my frames are left un-bonded to anything. the last thing I want is to be waving a flag at the next bolt of lightning to say HIT ME HERE and that is exactly what grounding the frames do.

    Each and every year I get about 20-30 hits within a few hundred feet of my home. Last year the street light got nailed and took out 2 inverters by backfeeding in the mains. That street light is less than 30 ft from the solar panels .. so I think its safe to say my preference saved my array/house from a direct hit!

    I'm not sure how John Wiles became an expert in lighting issues and best pratices of wiring to write regulations for the NEC, but where he lives I doubt he see the activity in his lifetime I see in one rainy season here in central florida.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Battery Grounding

    i agree with you on wiles even though i differ in my opinion of the need in grounding the pvs as we have discussed before and i understand and respect your opinion and how you came up with it. you may be in the lightning capital, but guess who's in second place? that's right, pennsylvania.
    in fact i'm going to add that even though the rods aren't tied that the grounds loops may still form depending on the soil conductivity and closeness of the rods to each other. what on earth is wiles thinking of?
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