Grounding roof mounted system - confused

[timselectric]

OK thanks. Just for me to understand from an electrical point of view:


What do you mean here? Say there is static on the frames, and the panels are connected to a ground rod, wouldn't the electron flow into the ground (so they are grounded), so if you touch the panel, you will be safe? Isn't this the meaning of grounding?

that would keep you from getting a Static shock.
But that's not the purpose of an electrical grounding system.

Would you then not have built the grounding grid next to the panels and simply run a 50 meter grounding cable from the panel frames to the ground system of the house?

The ground rods at the array are called auxiliary ground rods. While they are allowed by NEC, they are not required (nor recommended).
But if auxiliary ground rods are installed, they must also be connected to the existing grounding system.

If your answer is yes to that one, given I already built the grounding grid next to the panels and connected the frames to that, should I simply leave it but also run a 50-meter cable from the frames to the house?

You have two options.
1. Run a grounding conductor back to the existing grounding system. And connect it to the array and local ground rods.
2. Run a grounding conductor back to the existing grounding system. Connect it to the array and remove the local ground rods.
Option 2 is safer for your equipment at the house.
Because it's less likely to direct a gradient pulse (from a nearby lightning strike) to your equipment.

 

[bt77]

It's not going to catch all those faults but it will catch faults to the extent that the equipment and electrical code are able to do so. And quite a few solar faults related to grounding are detected but not auto-cleared. IE if things don't work or an alarm is raised you might want to presume that stuff is energized and test before touching.

Yes running EGC back in the same cable or conduit is the correct way. #10 should be good for almost all solar set ups unless you somehow have more than 60A for individual circuits (accounting for Isc adjustment etc). EGC in separate path is not code compliant but achieves similar safety, and TBH I think most people would rather the bond be put in in a hacky way than to not have one.

that would keep you from getting a Static shock.
But that's not the purpose of an electrical grounding system.

The ground rods at the array are called auxiliary ground rods. While they are allowed by NEC, they are not required (nor recommended).
But if auxiliary ground rods are installed, they must also be connected to the existing grounding system.

You have two options.
1. Run a grounding conductor back to the existing grounding system. And connect it to the array and local ground rods.
2. Run a grounding conductor back to the existing grounding system. Connect it to the array and remove the local ground rods.
Option 2 is safer for your equipment at the house.
Because it's less likely to direct a gradient pulse (from a nearby lightning strike) to your equipment.

OK, I can do Option 2 no problem. Easy to remove the rods, hopefully Well I can leave them in the earth but cut the connection from panel frames, right?

I will run a grounding conductor from panel frames back to the house in the same conduit the DC cables are running from panels to inverter then.

 

[JoeHam]

You think that way because you don't make a living as an electrician. Tim's way is the ONLY correct way to do it.

You are correct about me not being an electrician but this is a DIY forum so you’ll have that. I’m here to learn from anyone that knows more than me.

What is wrong with grounding your panels at the exact same place your house electrical system is grounded ?

I was never talking about ancillary ground rods etc, just the main house ground rod which I’ve always thought was appropriate.

 

[timselectric]

Well I can leave them in the earth but cut the connection from panel frames, right?

Yes
I would drive them down below grade, or cut them off.

 

[timselectric]

What is wrong with grounding your panels at the exact same place your house electrical system is grounded ?

nothing
But you are confused about where the electrical system is grounded.
That's at the N/G bond, not the ground rod.

 

[timselectric]

Most of the confusion around electrical grounding is the word "ground". Because we use that word to also describe the earth that we stand on.
But electrical grounding has nothing to do with the earth. Other than the fact that we also connect the earth to our grounding system. This makes the earth safe from a short on our electrical system.

 

[JoeHam]

But you are confused about where the electrical system is grounded.

I’m just a DIY guy so that is also a correct statement ?.

I have learned a lot about N/G ground over the years on the forum but I certainly have more to learn.

My only goal is to do things safely and I’ve never been afraid to put my ignorance on display to achieve that end. With that said let me get to describing my setup for grounding my panels.

So my N/G bond is at the main panel, inside my basement. It connects to the ground rod described below.

The system ground rod is outside the basement, less than 1 foot outside the basement wall.

Total distance from the N/G bond, inside the house to the ground rod outside, is about 3 feet total.

Would it be better to run my solar panel ground inside the house to the actual N/G ground instead of connecting at that ground rod described ?

 

[timselectric]

I’m just a DIY guy so that is also a correct statement ?.

I have learned a lot about N/G ground over the years on the forum but I certainly have more to learn.

My only goal is to do things safely and I’ve never been afraid to put my ignorance on display to achieve that end. With that said let me get to describing my setup for grounding my panels.

So my N/G bond is at the main panel, inside my basement. It connects to the ground rod described below.

The system ground rod is outside the basement, less than 1 foot outside the basement wall.

Total distance from the N/G bond, inside the house to the ground rod outside, is about 3 feet total.

Would it be better to run my solar panel ground inside the house to the actual N/G ground instead of connecting at that ground rod described ?

Either is fine, as long as the connection is good.
Inside connections don't have to deal with the outside environment. So, they are generally better and long lasting.
It's required by NEC to run the EGC with the PV wires, from end to end. But if not getting inspection, the outside connection will be just as good.

 

[bt77]

Most of the confusion around electrical grounding is the word "ground". Because we use that word to also describe the earth that we stand on.
But electrical grounding has nothing to do with the earth. Other than the fact that we also connect the earth to our grounding system. This makes the earth safe from a short on our electrical system.

Wait a second Saying nothing to do with the earth is a bit exaggerated, right?

I mean in a lot of places you will see the below definition (or similar) for electrical grounding:
"Electrical grounding is the process of creating an efficient pathway for electricity to discharge. It’s known as “grounding” because the electricity is typically guided to the ground where it’s able to discharge. Without grounding, electricity may build up inside of wires or connected devices to dangerously high levels. When this occurs, the wires or devices may arc. Grounding prevents this from happening by ensuring that excess electricity is safely discharged."
"The earth connection carries currents from the location of a fault (stray voltages, currents or electrostatic discharges) to the nearest earth ("dirt").
"Ground wiring is the wire in your cables that is intended to be earthed. It connects to metal casings, piping etc... via the third prong in plugs, but it is not a return wire for the live."

So isn't the whole point of grounding is to guide (discharge) faults, excess to the ground?

And this "guiding to the ground" is done by the rods, copper grids etc. we were talking about.

That's why I thought I could just create a second grounding grid next to the panels independent from the far away house ground, and ground them there.

Also, you guys keep mentioning the N/G bond. In Europe I'm not sure if neutral and ground are bonded together (or do they have to be?). As far as I know the utility provides the separate neutral line here and you build a grounding grid at your house and that's where your ground wire is connected,and all your equipment is grounded to that point.

 

[timselectric]

So isn't the whole point of grounding is to guide (discharge) faults, excess to the ground?

No
The purpose of the electrical grounding system is to provide a low impedance (resistance) path, back to the source (through the N/G bond).
This path allows protection devices (breaker or fuse) to clear the fault, before someone gets hurt.

 

[timselectric]

I mean in a lot of places you will see the below definition (or similar) for electrical grounding:
"Electrical grounding is the process of creating an efficient pathway for electricity to discharge. It’s known as “grounding” because the electricity is typically guided to the ground where it’s able to discharge. Without grounding, electricity may build up inside of wires or connected devices to dangerously high levels. When this occurs, the wires or devices may arc. Grounding prevents this from happening by ensuring that excess electricity is safely discharged."
"The earth connection carries currents from the location of a fault (stray voltages, currents or electrostatic discharges) to the nearest earth ("dirt").
"Ground wiring is the wire in your cables that is intended to be earthed. It connects to metal casings, piping etc... via the third prong in plugs, but it is not a return wire for the live."

This is completely wrong.
And scary.

 

[timselectric]

Also, you guys keep mentioning the N/G bond. In Europe I'm not sure if neutral and ground are bonded together (or do they have to be?). As far as I know the utility provides the separate neutral line here and you build a grounding grid at your house and that's where your ground wire is connected,and all your equipment is grounded to that point.

In Europe, the N/G bond is done by the utility company. And they provide the customer with a separate neutral and ground conductor.
In North America, the utility companies figured out that they could save money by making the customer do the bond. And then they can exclude the one conductor from every service drop.

 

[bt77]

In Europe, the N/G bond is done by the utility company. And they provide the customer with a separate neutral and ground conductor.
In North America, the utility companies figured out that they could save money by making the customer do the bond. And then they can exclude the one conductor from every service drop.

I'm confused again.

So you're saying the utility provides the ground line (color is yellow/green here in Europe) to the house? That can't be right. Here (countryside by the way) when you build a house you build an actual earthing system with electrodes, conductors, soil enhancers (to lower resistance) etc. As far as I know your ground line in your electrical panel connects to that earthing grid.

If the utility was already providing the line (earthed somewhere else, maybe transformer station), why would building an earth grid under or near the house be part of the house construction here?

 

[timselectric]

So you're saying the utility provides the ground line (color is yellow/green here in Europe) to the house?

Exactly

Here (countryside by the way) when you build a house you build an actual earthing system with electrodes, conductors, soil enhancers (to lower resistance) etc.

Correct, same for North America.

As far as I know your ground line in your electrical panel connects to that earthing grid.

It's actually the other way around.
The earth is connected to your grounding system.

If the utility was already providing the line (earthed somewhere else, maybe transformer station), why would building an earth grid under or near the house be part of the house construction here?

It's not that they provide an earthed conductor. It's that they provide the grounding conductor.
The connection to earth is very important.
It makes the earth around your house safe.
All that electricity wants to do is return to its source.
It won't dissipate or discharge into the earth.
Atmospheric static will.
But we're talking about electrical grounding for personal safety.

 

[Jim in Florida]

Just to make in confusing this is how our standard single phase power comes in.
The 2 black wires are 120v each and the bare aluminum wire is the ground from the local power company and the return (white wire) is bonded with the equipment grounds (bare copper) and the ground rod in this panel only. If a sub panel is installed then the grounds and white are separated.

 

[timselectric]

Just to make in confusing this is how our standard single phase power comes in.
The 2 black wires are 120v each and the bare aluminum wire is the ground from the local power company and the return (white wire) is bonded with the equipment grounds (bare copper) and the ground rod in this panel only. If a sub panel is installed then the grounds and white are separated.
View attachment 166936

Almost
The bare wire feeding the panel is the neutral.

 

[Jim in Florida]

 

[Jim in Florida]

I understand your confusion, I am American but have lived in England, Germany, Greece, and Turkey. When things go pop I always wanted to open and see if I could fix it. This was pre-internet to the wire colors were a mystery for a while.

 

[automatikdonn]

One grounding system, always.
It's not grounded, if kept separate.

Bingo!
Trust the Tim

 

[timselectric]

I understand your confusion, I am American but have lived in England, Germany, Greece, and Turkey. When things go pop I always wanted to open and see if I could fix it. This was pre-internet to the wire colors were a mystery for a while.

I'm not sure what you are pointing out.
Your drawing clearly shows the neutral feeding the panel.
A neutral is required to complete the circuit.
Unless it's a 240v circuit, on a split-phase system.
Or multiple legs of a 3-phase system.