Panel Grounding

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Joe J
Joe J Solar Expert Posts: 49 ✭✭
Is there any reason that you can't run a ground on the front face side frame work of your panels instead of the manufacture's grounding hole on the bottom of the panel? The aluminium sides seem to be square hollow stock or maybe an "H" stock of some sort. Pretty thick. You can feel where the grounding screw would come out on the other side far from the "glass" panel itself. I don't think this area is any kind of seal for the panel? The reason I ask is the panels are already down and tying to put the ground clamp to the bottom of the panel at this point would be a job and a half. I'm using #6 solid copper wire. Thoughts? I'm using these type of clamps that would have to have a polit hole drilled. http://webosolar.com/store/en/pv-grounding/806-burndy-grounding-lay-in-lug-tin-plated-cl501tn.html

While I'm at it I might as well edit this post and add a few more concerns. I plan to run the #6 wire direct from the PV panels to a 8 ft. ground rod. Than from inside the house tie in a ground to a transfer switch to the inverter to the controller to the breaker for the panels and out to that same ground rod. That's what I am thinking. Or should I tie the transfer switch to the main A/C box instead. I'm only talking about the ground from metal box to metal box. Make sense??

Joe

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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
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    Re: Panel Grounding

    Hi Joe J,

    I would NOT drill any additional holes in the frame of the PV Module. It is almost guaranteed to VOID the warranty. Normally.

    The Lay-In Lug that you linked looks close. BUT, to my eye, the set screw looks to be Zinc-plated steel. The absolute correct Lay In Lug is Tin-plated Copper, with a Stainless Steel set screw. These can cost between $5-$7 USD. If my guess is correct, this lug in the weather will corrode, and the set screw will rust.

    Opinions, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 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.
  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
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    Re: Panel Grounding

    Thanks Vic for writing. The link I posted was only the type or how the clamp looked. These are not the clamps I used. The ones I have are Tin-plated cooper with a SS set screw. Sorry, I should have cleared that up. Yes, I have heard that drilling the panel could void the warranty but I'm not really concern with that but more if I was going to break some kind of seal in the panel itself or a possible water inlet. Looks like the panel sits way up from where I want to drill so my thinking is it will have no real effect on the life of the panel. I been looking around at other people's set-up. I have not seen grounding wires to the side of the panel but I have seen metal brackets of one type or other used to mount them to a roof. So I'm thinking I'm okay??

    Joe
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
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    Re: Panel Grounding

    OK Joe,

    Yes you did say "type" of lug. Sorry that I took the link too literally.

    Grounding the PVs and any metal racking that mount the PVs is a very good thing to do. And if the system is to be inspected, it is almost always required. And this grounding can help reduce damage from near lightning strikes in some cases, and so on.

    I have little meaningful advice for your exact situation. Others may well have better ideas than I.

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 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.
  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
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    Re: Panel Grounding

    Thanks Vic. I always listen to what others say. Might learn something;) I know when you post something about grounding (second part of my question) your going to open up a can of worms. So many different views on the subject. Even if you talk to electricians many have differant ideas about what is right and wrong. Just like when you ask the solar guys about if you should ground the negitive side of a battery. I read yes..no...maybe! Personally I think you should ground everything. (maybe not the negitive battery post) Doing a search on the subject is enough to make you dizzy:confused:
  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
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    Re: Panel Grounding
    Joe J wrote: »
    Than from inside the house tie in a ground to a transfer switch to the inverter to the controller to the breaker for the panels and out to that same ground rod. That's what I am thinking. Or should I tie the transfer switch to the main A/C box instead. I'm only talking about the ground from metal box to metal box. Make sense??

    Joe

    Can anybody shed some light on the above statement? Thinking about this a little more maybe the better way to do this is to tie everything to one common buss bar than out to the ground so if one ground is broken the other equiment would not lose their ground. That's what we do in the radio "ham" world. Don't see why this would be any different. Also I have a manual transfer switch in my system. Should that go to the main A/C ground in the electric panel or to the D/C? ground rod just because it's part of that system?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Panel Grounding

    I am not sure I understand your question...

    With inverters and generators as backup power for Grid/Utility power--You cannot guess as to the correct method of grounding. You are limited by code and by the physical design and construction of the backup power equipment.

    For example, most MSW inverters cannot have neutral (white wire) tied to any sort of safety/earth ground--Especially if the battery bank (typically battery negative bus) is ground referenced too--It creates a dead short thought the inverter and will let out the magic smoke.

    With most TSW inverters, they have floating (or galvanic isolated) outputs (i.e., a isolation transformer) which can have one of its outputs safely tied to earth (and battery) ground. However, some TSW inverter appear to tie the case ground and neutral output together inside the inverter. This can cause "ground loop" problems with inverter ground bond and the ground bond inside the typical main service panel.

    Then through a generator in--and you have smaller gensets (under ~3.5 kW) that float their electrical outputs... And >~3.5kW which tie neutral to earth bond in the generator (to generator frame which then is connected to system/earth ground).

    So--You end up with different grounds (safety/green wire/conduit, AC, DC, inverter, generator, main panel, ground rod/water pipe, even RF/HAM grounds, etc.)... And you either have to use a 2 or 3 pole (120 or 120/240 split phase power) transfer switch to "transfer" the earth to white wire/neutral bond point (or even float the neutral for MSW type inverters)--Or you have to go into the devices and verify/lift earth to neutral bonding before connecting to the home's wiring.

    In a nutshell--Those are the questions... So, now what is your basic system block diagram you wish to implement?

    It is not a simple question/answer type thing.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
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    Re: Panel Grounding

    Hi Bill, I think we were writing at the same time. I'm only concerned with the safety ground to the ground rod not the neutral wire. I did an edit on my last post. Does this help to answer my questions??

    Joe
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Panel Grounding
    Joe J wrote: »
    Than from inside the house tie in a ground to a transfer switch to the inverter to the controller to the breaker for the panels and out to that same ground rod. That's what I am thinking. Or should I tie the transfer switch to the main A/C box instead. I'm only talking about the ground from metal box to metal box. Make sense??
    Can anybody shed some light on the above statement? Thinking about this a little more maybe the better way to do this is to tie everything to one common buss bar than out to the ground so if one ground is broken the other equipment would not lose their ground.

    More or less--We are looking to tie the ground in "one place" If that is a "ground window" (term used in telephone central offices--basically from what I can tell, a big bus bar/group of bus bars that are all defined as telecom "ground" for the building.

    If all grounds are home run back to this one (i.e., no parallel ground paths such as a ground wire from the battery bank negative, and another ground wire from a car radio where DC return/chassis ground are the same thing).

    Then run a single cable from that ground window to a near by ground rod/earth ground would be fine.

    The one caution is a question of safety vs lightning grounds. Lightning is RF energy (~7.5kHz maximum frequency from what I could find)--So any outside systems/components/metal structures should go straight down to an earth ground rod/plate. Brining a ground that may be subject to lightning inside a home is usually a "bad idea".

    If you have "multiple grounds" that are both Lightning related and "safety related" (i.e., you have AC or DC power sent to equipment/lighting/etc. at the base of an antenna tower or out building). You can carry the "green wire" safety ground" from the primary power location (i.e., in your home) out to the equipment so you get ground protection against hot to metal faults--will pop fuse/breaker and isolate from local lighting ground). Or you can bring out a separate ground wire from the home ground rod out to the outbuilding ground rod. The local ground rods will provide lightning ground. And the ground rod to ground rod cable will provide the AC or DC safety ground connection.
    That's what we do in the radio "ham" world. Don't see why this would be any different. Also I have a manual transfer switch in my system. Should that go to the main A/C ground in the electric panel or to the D/C? ground rod just because it's part of that system?

    So--Sorry to be so dense... Are you talking about the metal box for an AC transfer switch, or the Neutral, or even talking about a transfer switch on a green wire ground?
    Than from inside the house tie in a ground to a transfer switch to the inverter to the controller to the breaker for the panels and out to that same ground rod. That's what I am thinking. Or should I tie the transfer switch to the main A/C box instead. I'm only talking about the ground from metal box to metal box. Make sense??

    And is the inverter a floated AC neutral or a MSW with DC bus grounded (to common ground rod or AC vs DC ground rod with a 6 awg cable between the two rods, etc.)?

    What controller (battery charge controller?). What breaker panels (DC or AC, or Solar Combiner)? What "same ground rod" (AC ground rod for home panel, separate DC or AC ground rod for backup power system? Will separate ground rods be tied together with 6 awg cable?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
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    Re: Panel Grounding
    BB. wrote: »
    So--Sorry to be so dense... Are you talking about the metal box for an AC transfer switch, or the Neutral, or even talking about a transfer switch on a green wire ground?


    And is the inverter a floated AC neutral or a MSW with DC bus grounded (to common ground rod or AC vs DC ground rod with a 6 awg cable between the two rods, etc.)?

    What controller (battery charge controller?). What breaker panels (DC or AC, or Solar Combiner)? What "same ground rod" (AC ground rod for home panel, separate DC or AC ground rod for backup power system? Will separate ground rods be tied together with 6 awg cable?

    -Bill

    Yes Bill, I'm talking about the metal box from the AC transfer switch. I have a prue sine wave 2000 watt Xantrex Prowatt inverter with a Midnite classic controller.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,478 admin
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    Re: Panel Grounding

    If your transfer switch is tied to grid power--yes, just tie the metal box to the green/wire of your main power panel--You are fine. If there is a short, the energy is dumped back to the main panel (and pops the breaker).

    The output of the TSW inverter is "floating"--You you have the choice of ground referencing its neutral output or even just carrying the neutral from the main panel through to the protected loads.

    I believe the Xantrex floats the AC output with respect to ground(s)--But you need to read your manual and check with a meter to be sure.

    A 2kW inverter is just right on the edge of needing a distribution box/breakers for its output (can exceed the 15 amp max/12 amp max continuous current rating of 14 AWG wiring).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Joe J
    Joe J Solar Expert Posts: 49 ✭✭
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    Re: Panel Grounding

    Thanks a lot Bill. Just what I needed to know.