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diy solar

Extra/Auxilary grounding rods..... Don't do it.

hwy17 said:
Yes open neutral faults. But it seems so much more likely to me that the messenger wire on my triplex service drop will snap one day compared to anything happening to my outbuilding neutral in conduit.
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Your drawing shows the neutral bonded in two places and earthed in two places.
200% what you want to avoid.
If the neutral is lost , the earth will try to carry the neutral current. This creates a step Hazzard. Two feet on the earth is a less resistive path than the earth between the feet. People become part of the circuit.
 
You guys who are master electricians are looking at it from an electricians point of view, and that's good. I think a majority of folks are thinking of lightning protection however, and that's where the conflicting (dis?)-information comes in to play. At a properly designed tower installation, we ground everything...even the fence, and the gate has copper braid bonding across the hinges. If I were to install a metal ground mount in an area prone to lightning strikes, I'd have several grounds cad welded to the metal support pipes to divert the energy from a direct strike away from the supports. I have seen concrete piers fractured from the moisture in the concrete being flash vaporized. Attached is some light reading.
 

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timselectric said:
If the neutral is lost , the earth will try to carry the neutral current. This creates a step Hazzard. Two feet on the earth is a less resistive path than the earth between the feet. People become part of the circuit.
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This is the same as if you lose your Triplex neutral though. I don't think it ever commonly causes actual shocks at 120/240 voltage, just fries stuff in the house as it all turns into 240v in series. Like I get the theory, but open neutral is already a regular and accepted hazard potential for a house so I don't see why an outbuilding is so different. I do see why we changed it, but I don't worry about my outbuilding on old three wire service.
 
Brett V said:
You guys who are master electricians are looking at it from an electricians point of view, and that's good. I think a majority of folks are thinking of lightning protection however, and that's where the conflicting (dis?)-information comes in to play. At a properly designed tower installation, we ground everything...even the fence, and the gate has copper braid bonding across the hinges. If I were to install a metal ground mount in an area prone to lightning strikes, I'd have several grounds cad welded to the metal support pipes to divert the energy from a direct strike away from the supports. I have seen concrete piers fractured from the moisture in the concrete being flash vaporized. Attached is some light reading.
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There's a difference between lighting protection and electrical safety grounding.
Lighting protection is used to divert lighting around or away from what you want to protect.
You should never use what you want to protect as part of the lighting protection path.

Nothing we discuss about solar grounding has anything to do with lighting protection. (That's a totally different system)
It's only about electrical safety grounding.
 
timselectric said:
There's a difference between lighting protection and electrical safety grounding.
Lighting protection is used to divert lighting around or away from what you want to protect.
You should never use what you want to protect as part of the lighting protection path.

Nothing we discuss about solar grounding has anything to do with lighting protection. (That's a totally different system)
It's only about electrical safety grounding.
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I agree but I think a lot of folks link the two practices and get confused.
 
So for the sake of discussion, electrical safety grounding requires recommends a ground from the PV array to only be carried to the single point earth ground for the building. Lightning protection requires bonding the PV array to a local earth ground, and I'd really prefer to not provide an easy path for lightning from the PV array to the building. They seem mutually exclusive yet both correct.
 
Brett V said:
Lightning protection requires bonding the PV array to a local earth ground
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No, that is what is confusing people.
Lighting protection requires separate air terminals mounted above and around what you want to protect.
Only the air terminals are connected to the local earth. (It's actually more complex, but I simplified it)
 
timselectric said:
No, that is what is confusing people.
Lighting protection requires separate air terminals mounted above and around what you want to protect.
Only the air terminals are connected to the local earth. (It's actually more complex, but I simplified it)
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So in my scenario, the radio tower itself would probably be the separate air terminal...that makes sense.

And I'm not intending to muddy the waters, I realize grounding practices for a large radio tower don't apply to the guy putting a ground mount PV array in his back yard. I wonder how it's done at a large commercial solar farm?
 
So maybe this is a stupid question, but doesn't this apply in a similar way to having a grounding rod for a ground-mount solar array?

My amateur understanding has always been you want a single grounding point for your whole electrical system, which under normal residential circumstances tends to be near your feed from utilities/main breaker, everything is tied back here, and you do your NG bond in the main breaker panel.

As in, it seems like a bad idea to have a grounding rod at my shed if I am running electrical service from my home to a sub panel out there. Isn't the idea that my grounding would simply be via the ground wire back to my main panel? Shouldn't the same hold true with grounding a ground-mount array? Wouldn't you want a separate ground wire run along with your PV wire that's tied back into the grounding? I've see people talking about separate grounding rods for this.

Mostly looking for some understanding on this, as to me it seems like the same thing as the shed example.
 
Think of the shed as an extension cord with an outlet strip plugged in to the end, it's basically the same thing. You wouldn't drive a separate ground rod for your outlet strip.

In the case of the ground mounted PV array, it gets grounded back to the main service in the same way. The goal is anything metal is at the same ground potential so no currents can flow on them and cause a shock.
 
Dagoth Ur Does Solar said:
So maybe this is a stupid question, but doesn't this apply in a similar way to having a grounding rod for a ground-mount solar array?

My amateur understanding has always been you want a single grounding point for your whole electrical system, which under normal residential circumstances tends to be near your feed from utilities/main breaker, everything is tied back here, and you do your NG bond in the main breaker panel.
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This is correct.
Dagoth Ur Does Solar said:
As in, it seems like a bad idea to have a grounding rod at my shed if I am running electrical service from my home to a sub panel out there. Isn't the idea that my grounding would simply be via the ground wire back to my main panel?
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Yes, you are correct in your thinking. However, NEC requires a ground electrode at a structure.

Dagoth Ur Does Solar said:
Shouldn't the same hold true with grounding a ground-mount array? Wouldn't you want a separate ground wire run along with your PV wire that's tied back into the grounding?
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No ground rod at the array.
Dagoth Ur Does Solar said:
I've see people talking about separate grounding rods for this.
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People like to put ground rods everywhere, reality is those ground rods aren't accomplishing the intended purpose of clearing a ground fault.

Dagoth Ur Does Solar said:
Mostly looking for some understanding on this, as to me it seems like the same thing as the shed example.
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NEC requires a ground rod at a building structure with a feeder currently. Whether this changes in future NEC requirements, we will find out.
 
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Brett V said:
Think of the shed as an extension cord with an outlet strip plugged in to the end, it's basically the same thing. You wouldn't drive a separate ground rod for your outlet strip.

In the case of the ground mounted PV array, it gets grounded back to the main service in the same way.
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Yes, that's right along the lines I was thinking. Single point of grounding for anything electrically connected.

Brett V said:
The goal is anything metal is at the same ground potential so no currents can flow on them and cause a shock.
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That's exactly why I can't wrap my head around why you would ever want an auxiliary grounding rod. To my uneducated brain, this seems at best, a bad idea, and at worst, dangerous?
 
Quattrohead said:
Not a chance.
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You haven't read the threads. :)

As Filter Guy and Tim noted, no one can come up with a definitive reason for the ground rod on a feeder circuit to another building structure.

Do you have the answer to this question other than, "we have always installed a ground rod at a separate building panel"?
 
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Zwy said:
You haven't read the threads. :)

As Filter Guy and Tim noted, no one can come up with a definitive reason for the ground rod on a multiwire feeder circuit to another building structure.

Do you have the answer to this question other than, "we have always installed a ground rod at a separate building panel"?
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I would guess the answer is without it, you don't get that inspection sticker attached to the service panel.
 
Mike Holt was instrumental in getting the code changed in 2017 after he brought up the problems with 690.47 This video still applies when it comes to auxiliary ground rods.

 
I made the time to watch the videos, and it definitely confirmed my intuition on this.

Great videos. Knowing how government bodies work, it'll probably take someone in an AHJ where this is being enforced actually dying from it to get it changed.
 
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hwy17 said:
But this is my fault current path inside the outbuilding. It rides the outbuilding EGC onto the neutral and the neutral back to the source.

Now faults that happen in between House and Outbuilding gets more complicated. I am used to it being PVC conduit. If it was metal conduit that would complicate things. I don't even know how they 3 wire subpanels with metal conduit, the metal would carry regular neutral current. Maybe you're talking about these complexities in between.

View attachment 203424
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You’re image is missing the ground rod at the transformer
 
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