Proper Grounding.

[jbkrntrprz]

You can't put a price on Safety.
Life is priceless

Is something I'm doing here unsafe? Right now I have the PV rack grounded at the site and everything else grounded to one rod at the house. Some people say everything to one grounding rod and others say its ok to do what I have done. Seems fine to me but you are the expert. I also appreciate that knowledge which sometimes gets transferred over to my brain cells!

 

[timselectric]

Is something I'm doing here unsafe? Right now I have the PV rack grounded at the site and everything else grounded to one rod at the house. Some people say everything to one grounding rod and others say its ok to do what I have done. Seems fine to me but you are the expert. I also appreciate that knowledge which sometimes gets transferred over to my brain cells!

Electrical grounding is for personal safety. (To avoid getting shocked)
The purpose of the grounding system is to provide a low impedance (resistance) path back to the source. So that a breaker or fuse can clear the fault before someone gets hurt.
This path is made by bonding (connecting) everything conductive (metal) together with EGC's. To form a complete grounding system.
The fault current path is completed at the N/G bond.

A separate connection to earth does not provide the low impedance path for ground fault current.
Because the earth is a terrible (very high resistance) conductor.
And provides zero protection for people from a possible shock hazzard.
Even worse, it gives people a false sense of security.

 

[jbkrntrprz]

Electrical grounding is for personal safety. (To avoid getting shocked)
The purpose of the grounding system is to provide a low impedance (resistance) path back to the source. So that a breaker or fuse can clear the fault before someone gets hurt.
This path is made by bonding (connecting) everything conductive (metal) together with EGC's. To form a complete grounding system.
The fault current path is completed at the N/G bond.

A separate connection to earth does not provide the low impedance path for ground fault current.
Because the earth is a terrible (very high resistance) conductor.
And provides zero protection for people from a possible shock hazzard.
Even worse, it gives people a false sense of security.

Ok, so I guess I'll get rid of the ground at the panels and run the 130 ft of grounding wire thru conduit and connect it to the ground rod at the house which is connected to the N/G bond.

 

[timselectric]

Ok, so I guess I'll get rid of the ground at the panels and run the 130 ft of grounding wire thru conduit and connect it to the ground rod at the house which is connected to the N/G bond.

Anywhere on your existing grounding system is fine to connect to. (Doesn't have to go to the existing ground rod, unless that's the easiest place)
As long as what you connect to is as large or larger than what you are connecting.

 

[SSC00]

Anywhere on your existing grounding system is fine to connect to. (Doesn't have to go to the existing ground rod, unless that's the easiest place)
As long as what you connect to is as large or larger than what you are connecting.

so you don't have to run it all the way back to your breaker panel ground rod if the distance is great enough?

 

[timselectric]

so you don't have to run it all the way back to your breaker panel ground rod if the distance is great enough?

You must connect to the grounding system. The ground rod is just one part of the grounding system.
Once something is connected to the grounding system it becomes part of the grounding system. And can be used as a connection point for additional EGC's.
Your PV circuit conductors (and EGC) will run to your solar equipment area (SCC, Inverter). You should already have part of the grounding system there, to connect to.

 

[Bluedog225]

The 6' minimum rule is for two rods used as a single point of connection to earth. (At the service)
There's no distance requirements for an auxiliary ground rod. You can drive ten in the same hole. Or place them 100 miles apart. The reason that there are no requirements is because they serve no purpose.

I’d like to make sure I understand your point. And ask a question.

Do you recommend two rods as a single point of connection to the earth (at the service)?

And do you recommend a deeper grounding rod than the 8’ rods generally available? And what is the proper name for those rods with threaded ends? I don’t want to sound dumb at the electric supply house.

Thanks

 

[timselectric]

Do you recommend two rods as a single point of connection to the earth (at the service)?

It's not my recommendation.
It's an NEC requirement. Unless you can prove the under 25 ohms resistance. (It's easier to just drive the second rod)

And do you recommend a deeper grounding rod than the 8’ rods generally available?

No

 

[Bluedog225]

Got it. I wanted to make sure I didn’t misunderstand your comment about an auxiliary ground rod.

Thanks

 

[timselectric]

Got it. I wanted to make sure I didn’t misunderstand your comment about an auxiliary ground rod.

Thanks

Don't get confused between supplemental (sometimes required), and auxiliary (never required).
The second rod at a service is a supplemental electrode.
The rod that people feel they should put at a solar array is an auxiliary electrode.

 

[Bluedog225]

Got it. There’s a lot of careless use of terminology on the interwebs. I’m (slowly) leaning the fairly precise lingo of the NEC and electricians.

 

[SSC00]

You must connect to the grounding system. The ground rod is just one part of the grounding system.
Once something is connected to the grounding system it becomes part of the grounding system. And can be used as a connection point for additional EGC's.
Your PV circuit conductors (and EGC) will run to your solar equipment area (SCC, Inverter). You should already have part of the grounding system there, to connect to.

Ok. So if I ground my inverter to my subpanel and my sub panel to my main panel's ground do I need to run a third wire from my ground mount PV system (its maybe 30 ft from my house) to ground it or is it grounded just by connected to the grounded inverter?

 

[Bluedog225]

The translation from electrician’s language to layperson is tough sometimes.

Most importantly, listen to Tim and not me. But I’ll take a shot to test my understanding.

All your stuff (equipment) needs to be bonded together. And all that stuff is also bonded to your earth ground/ground rod.

Your panels need to be bonded to your other bonded stuff. Not by the positive and negative current carrying conductors. But instead by a wire dedicated to bonding. That is, yes you need a third wire from your ground mount PV frames and racking to your grounding system.

The whole grounding deal (grounding system) is a separate thing from the positive and negative from your panels. And separate from the alternating current your inverter produces. Everything bonded together with a separate wire. Panels, framers, metal boxes, metal shelves, metal building, etc). And only once into the earth. That’s why Tim says “Your PV circuit conductors (and EGC)”. He’s saying positive, negative, and the equipment grounding conductor (the third wire you reference).

Apologies to Tim and others if I butchered the proper terminology.

And please wait for someone more knowledgeable than me to confirm.

 

[timselectric]

Ok. So if I ground my inverter to my subpanel and my sub panel to my main panel's ground do I need to run a third wire from my ground mount PV system (its maybe 30 ft from my house) to ground it

3rd wire, as in + , - , G ?
Yes, this is how you ground your array.

or is it grounded just by connected to the grounded inverter?

Not without an EGC. (Ground wire)

 

[SSC00]

3rd wire, as in + , - , G ?

ok so i do need to get a third wire - a green one - to ground the system properly or I get a nasty shock without expecting it. lol

I can do it with a 12 AWG THHN wire right?

 

[Bluedog225]

I think this question of in scope of this thread.

How much continuity is sufficient? For example, if I can measure basic continuity with a multimeter to various parts of my solar mounting equipment, light fixture, or wire shelf, or whatever, is that always sufficient?

I’m fairly sure some parts are not well bonded. And will become less well bonded over time. Due to corrosion.

Does it matter as long as I can measure continuity?

This seems like a weak point from a safety perspective.

Thanks

 

[Bluedog225]

ok so i do need to get a third wire - a green one - to ground the system properly or I get a nasty shock without expecting it. lol

I can do it with a 12 AWG THHN wire right?

I think yes. The ground can be a little smaller than the current conducting wires. Because it only carries momentary current before the over current protection device cuts power. In theory. Assuming you have a protection device.

There are rules on sizing the egc. I don’t know then.

Edit-i’m also guessing that if you size your ground wire at the same size as your current carrying conductors, you have a safe harbor. Again, I’m just guessing.

 

[jbkrntrprz]

3rd wire, as in + , - , G ?
Yes, this is how you ground your array.

Not without an EGC. (Ground wire)

Getting ready to dig that 100ft trench to run that ground wire to my house. I also am using 10 AWG. I'll be pulling out that existing rod at the PV rack. I'll need it to beat myself over the head with.

 

[timselectric]

I think this question of in scope of this thread.

How much continuity is sufficient? For example, if I can measure basic continuity with a multimeter to various parts of my solar mounting equipment, light fixture, or wire shelf, or whatever, is that always sufficient?

I’m fairly sure some parts are not well bonded. And will become less well bonded over time. Due to corrosion.

Does it matter as long as I can measure continuity?

This seems like a weak point from a safety perspective.

Thanks

Preferably 0.00

 

[timselectric]

I can do it with a 12 AWG THHN wire right?

See chart below