Earth grounding : common vs separate

ALL NEW - Battery Finder Search for 12/24/36/48v or by capacity www.batteryfinder.net
New & used Batteries, Solar, accessories, LifePo4 cells & more 5% Coupon "Powerwalls" www.batteryhookup.com
Overmind

Overmind

Member
Joined
Jan 16, 2019
Messages
494
In recent months in my area this debate has become as close to a political debate anything can get.

Some electricians say you need separate earth grounding for the solar panels and even more: to have minimal distance from PV grounding to the house grounding.
The other faction is saying you need to make a common one, with the extreme of connecting both ground pylons and actual connections between the 2 systems.

Using logic, I tend to agree with the 1st option, since the panels & rails are a completely isolated DC system from the house's AC system.
Also, the 2 can get quite different "encounters" and I find no logic in eventual DC flow into an AC system or having AC run through my roof.

Please ignore my own view on this and state your own.
 
Last edited:
Ground mounted systems are automatically grounded if using prefab installation racks. The metal racks are all locked together then the metal poles are stuck in the ground. So there's that....

I personally think it's a bad idea to have "house wiring" carry any form of possible lightning strike as it is usually not large enough gauge to handle that wattage. It can be well over 10kW, if not over 100kW or 1MW of power. In my mind, by using the house wiring to do the grounding is not a safe way to handle that high power surge.
So I'd say personally ground the panels independently, regardless if ground or roof mounted. This doesn't mean that it can't also be connected to the house ground as well. But definitely have it's own path to ground; even if that dedicated wire runs directly to the primary house rod as well.
 
I know what you mean - this topic goes round and round and round. :D

I have a single ground to the house ground for everything. This is how the electrician for the city permit wired the roof array and I followed thru when doing the ground array. However, the ground array has 8 x 2" vertical galvanized pipes that are 36" deep into the ground / concrete ballast - so maybe some lightning would find it's way into ground?

I DO have 4 x lightning arrestors on each set of wires going into the house from the arrays - so maybe this will help slow down a surge into the house itself.

In any case, my strong opinions is.... I think one should have a ground one way or the other as this is better than no ground at all :)
 
I'm now looking into this topic! 🤮 (Like trying to read a book with pages made of sandpaper.) I think the biggest problem with the whole 'debate' is there are few qualified and quantified resources available (and/or an overabundance of unbacked opinions) I'm talking about my peek into the abyss, I mean internet! I really appreciate the above replies as it helps me fill in some of the reasoning and methods for grounding.

I'd like to collect more of the reasoning for or against.

For me, I'm starting from the point of What is is being accomplished in the event of:

- direct lightning strike: Agree, with you Korishan. I don't want a strike finding its way into/through my AC electrical system.

Also, I want to limit the damage to the DC side as much as possible. OffGridInTheCity, where are your lightning arresters located in your system? Could you tell me the type you're using? (answered in future post: MidNite Solar MNSPD-300-DC Surge Protection Device)
🤔:) Is it protecting your mppt?

Other thoughts... most(99%??) grounding wouldn't handle a direct strike. I think if you're in an area prone for strikes you need to be looking at a different way to handle that. (a.k.a lightning prevention system)

wiki with info on how to safeguard inverters/BMS: https://github.com/dalathegreat/Battery-Emulator/wiki/Lightning-strike (Thanks Dala!)
- nearby strike: Nearby strikes can damage AC & DC equipment.

I know that if you have multiple nonconnnected grounding rods. Backfeeding can occur up one grounding rod, through the house, and back through another rod, due to following the path of least resistance and voltage gradients in the physical earth/soil/land. Tieing auxiliary (PV) ground rods via a dedicated wire to your main ground rod reduces this risk.

Are there other ways nearby strikes damage equipment? ((See last link! )

- static electricity buildup This is one of the main reasons I want to ground my panels. Grounding helps dissipate static. I fully understand this side of the argument from past work with sensitive electronics.
- fault in the panels or between the panels not sure about this
- faulty mppt, inverter, etc. that somehow engergizes the PV array I think this is why a lot of local building codes are requiring the PV to be grounded) Perhaps rare, but at least I understand the reasoning.

Okay, so this is mostly just information I've gleaned from the abyss, err I mean Internet. I'd like to update/add/correct/edit it.

Are there other reasons (for or against), not listed above?
 
Last edited:
It looks like the cheaper inverters may not have good isolation between the Panels and AC H-bridge. Even though you wouldn't expect AC voltage on you panel/panel mounts, it can happen...
View: https://www.youtube.com/watch?v=DohWzgiSfgo


My thinking is that in this case grounding is fixing a symptom, not the problem... Personally, I would aim for a better inverter. (edit... check out @JDWolfe-m92 comment about the voltage reading (in the comment section of the video) in this particular case.)
 
Last edited:
Fukuokian said:
- direct lightning strike: Agree, with you Korishan. I don't want a strike finding its way into/through my AC electrical system.

Also, I want to limit the damage to the DC side as much as possible. OffGridInTheCity, where are your lightning
arresters located in your system? Could you tell me the type you're using? 🤔:)Is it protecting your mppt?
Click to expand...
I have 5 x combiner points out at the arrays = 5 x pairs of wires going thru the wall of the home (in conduit). Early on I read about the wisdom of Lightning protectors so I went with Midnite Surge (Lightning) Protectors at each each pair of wires going into the home from the combiner boxes (easy place to install / hook them up) near the arrays.

I'm using these - https://www.amazon.com/gp/product/B00SGGWAZ8/ref=ppx_yo_dt_b_search_asin_title
1734191957850.png


They protect both positive and negative wires and also connected to the common ground.

**I've never had a lightening or surge event - but the "Midnite" name is a genuine/serious name in the solar space so I'm hoping these units provide a measure of safety to keep a surge from traveling down the wires that penetrate the home.

There's a youtube channel (@Tiny Shiny Home) where they're offgrid system apparently suffered a surge via lightning hitting ground / causing a surge thru wires under the ground and burned up his Victron stuff.
View: https://youtu.be/7DvIjAvMge0?si=y6bdNK_7UsPjPBv2

Hard to protect against every possible scenario!
 
Last edited:
OffGridInTheCity said:
I have 5 x combiner points out at the arrays = 5 x pairs of wires going thru the wall of the home (in conduit). Early on I read about the wisdom of Lightning protectors so I went with Midnite Surge (Lightning) Protectors at each each pair of wires going into the home from the combiner boxes (easy place to install / hook them up) near the arrays.

I'm using these - https://www.amazon.com/gp/product/B00SGGWAZ8/ref=ppx_yo_dt_b_search_asin_title
View attachment 32785

They protect both positive and negative wires and also connected to the common ground.

**I've never had a lightening or surge event - but the "Midnite" name is a genuine/serious name in the solar space so I'm hoping these units provide a measure of safety to keep a surge from traveling down the wires that penetrate the home.

There's a youtube channel (@Tiny Shiny Home) where they're offgrid system apparently suffered a surge via lightning hitting ground / causing a surge thru wires under the ground and burned up his Victron stuff.
View: https://youtu.be/7DvIjAvMge0?si=y6bdNK_7UsPjPBv2

Hard to protect against every possible scenario!
Click to expand...
I just watched this video and was going to post it! Cool
 
I feel your pain how there is so little good well backed resources on how to handle grounding across the board.

I have read lots of reports that make me suspicious of the actual real world effectiveness of all surge protection devices I have researched although the Midnight solar one does seem like the most trustworthy of them all even though their flashy youtube video showing how it works is not actually convincing replication of a real world event.

One big thing I have heard very consistently talked about in regards to why all earth grounding should go to one central place is because it changes and equalizes the earth voltage such that is makes lighting strikes less likely to form in the first place by dissipating that energy and charge build up before it becomes a strike. There are of course other reasons for one central ground related to how AC breakers work to name only one that is on my mind. This also doesn't apply to "floating" dc systems that don't have a earth ground but when done correctly can be very safe for the right situation.

As a side note I have lived off grid my whole life and we have had several lightning strikes that fried equipment all of which were because of a wind tower we were using for electrical generation which for many reasons we no longer use and haven't had an issue since we disconnected it from our system. After the first strike and getting the inverter rebuilt we did implement some extra protection systems some of which was to physically isolate the wind tower from the system whenever a storm was near. This was many years ago so I don't remember most of the details.
 
I have been and seen one lighting going out of the earth (pond of 100.000 liters) ozon smell was all around...and several going into the earth.
Now the Netherlands is basically a floating piece of dirt.
When i am driving a grounding rod i hit in our dryest season of the year water at not even 3 meters deep.
(where I AM located!!(noord holland, Netherlands), Limburg Gelderland are different stories, up to 30 meters...some place even deeper)

In that vid of the guy in the dessert how deep he must go to hit water?
How deep did he go? not even 5 meters?
Electricity will always find the way of the least resistance, in case of that dessert guy its the next pole/rod, in my case it will be the mass of a lot of water.
I think this is a two maybe even a 15 way approce to get rid of the extra electricity and surge.
I think (I)we are very lucky to have such low ground water levels...
(Drinking water is 17 meters deep btw, 23 meters deep is salt, above 15 to 12 there is not much movement of water, above 12 its drinkable above 9 it is junk.)

I think if you put your rod (if you have any ground water) deep enough into the ground water you can redirect a small surge.
Even having two rods the surge will go to the mass and not to the other rod?

a steel rod with a zinc coating will do - 24mm can be driving into the ground with a concrete drill, get a bus to connect a other rod and add 3 meters?

I am talking only what is possible in OUR/mime surcumstances.....
I hope this will help some of you.

With best regards Igor, be safe its better than sorry and what if!
 
Came across this one:
View: https://youtu.be/_xOUEKehOFE


Pretty informative and straight to the point. If using multiple grounding points, it's required to have them bonded. Those in the ground, and those above the ground (panels, sub-panels, etc). This eliminates the possibility of voltage potential of occurring between two grounding rods.
 
Korishan said:
Came across this one:
View: https://youtu.be/_xOUEKehOFE


Pretty informative and straight to the point. If using multiple grounding points, it's required to have them bonded. Those in the ground, and those above the ground (panels, sub-panels, etc). This eliminates the possibility of voltage potential of occurring between two grounding rods.
Click to expand...
Nice reminder that ground wiring is not just for lightning but for ground fault protection.

On the lightning / surge inducement side, I don't get the 'dissipation' angle very well. For example....

My arrays are bonded, and I think of them as a big metal lattice - e.g. a big metal framework all bonded together. From my arrays there's a 'single' wire o the house ground. This 6awg wire from roof array to main panel/house ground is about 15ft. The 6awg wire from the ground array is about 50ft and then connects into the house ground and goes another 100ft to the main panel / ground.

Side notes....
- I do have these Midnite Surge protectors at the combiner boxes at the arrays and they 'protect' the + and - wires going into the house but also connect to the array ground wire I talk about above.
- The yard array has 2" galvanized pipe supports... there are 8 of them about 36" into concrete in the ground - can these dissipate some of a lightning strike?

What I don't get is it seems like lightning needs something like 4/0 AWG to carry the voltage? current? to 'the ground' for dissipation but I don't think I've seen more than 8awg or 6awg for ground wires and my own system is 6awg to maybe 8awg inside the house. Can one really expect lightning to travel 150ft over 6awg wire thru the main panel / home ground for dissipation?
 
Last edited:
OffGridInTheCity said:
Nice reminder that ground wiring is not just for lightning but for ground fault protection.

On the lightning / surge inducement side, I don't get the 'dissipation' angle very well. For example....

My arrays are bonded, and I think of them as a big metal lattice - e.g. a big metal framework all bonded together. From my arrays there's a 'single' wire o the house ground. This 6awg wire from roof array to main panel/house ground is about 15ft. The 6awg wire from the ground array is about 50ft and then connects into the house ground and goes another 100ft to the main panel / ground.

Side notes....
- I do have these Midnite Surge protectors at the combiner boxes at the arrays and they 'protect' the + and - wires going into the house but also connect to the array ground wire I talk about above.
- The yard array has 2" galvanized pipe supports... there are 8 of them about 36" into concrete in the ground - can these dissipate some of a lightning strike?

What I don't get is it seems like lightning needs something like 4/0 AWG to carry the voltage? current? to 'the ground' for dissipation but I don't think I've seen more than 8awg or 6awg for ground wires and my own system is 6awg to maybe 8awg inside the house. Can one really expect lightning to travel 150ft over 6awg wire thru the main panel / home ground for dissipation?
Click to expand...
In the video (
View: https://youtu.be/_xOUEKehOFE
)Korishan linked above, the presenter talks about direct strikes are going to do damage to a PV array. You would need to look at a different system (lightning protection system: https://ecle.biz/what-is-lightning-protection/) to handle direct lighting strikes. I agree 6awg 8awg etc isn't going to do much dissipation.

People don't realize that a lot of damage is done by nearby strikes, for which grounding has the secondary benefit of preventing/reducing damage.

I think it may be better to say that ground wiring an array is not really for lightning... it does have some benefits for nearby strikes and may reduce some damage for direct strikes, but it's primary purpose is fault protection.

Caveat: Unverified -> I read somewhere -- (As cak also said) sorry no link -- that connected ground rods may actually help prevent lightning (direct hits). Basically by helping to balance/distribute/reduce the ground portion of the charge differential. So maybe
My arrays are bonded, and I think of them as a big metal lattice - e.g. a big metal framework all bonded together.
Click to expand...
is working for you! ;)


Good lightning info here... https://www.nssl.noaa.gov/education/svrwx101/lightning/faq/
 
Last edited:
Korishan said:
Came across this one:
View: https://youtu.be/_xOUEKehOFE


Pretty informative and straight to the point. If using multiple grounding points, it's required to have them bonded. Those in the ground, and those above the ground (panels, sub-panels, etc). This eliminates the possibility of voltage potential of occurring between two grounding rods.
Click to expand...

Great find!!

Is it possible to pin this somewhere in the FAQ section. Definitely deserves a sticky!
 
Hahah, amazing when you start down a rabbit hole, videos start showing up on YT, even new ones just posted :LOL:

Clipped Video from Jeff's video about AM radio antennas

youtube.com

✂️ Ground Rods

60 seconds · Clipped by Korishan (Korishan) · Original video "Why is the invisible part of this radio tower so important?" by Geerling Engineering
youtube.com youtube.com

The whole video is very interesting. Recommend watching the whole thing.
 
You must log in or register to reply here.
Back
Top