Grounding roof mounted system - confused

[Supervstech]

The ground fault protection at the inverter will only operate correctly if it can see a connection between its ground and the metal components on the array.

This is incorrect...

Ground fault has NOTHING TO DO WITH THE GROUND WIRE...

ground fault devices will trip when there is an imbalance of energy between the conductors.

If more energy is transmitting on the hot wire than is returning on the neutral or other hot wire, the gfci will interrupt the current.

It does not require a ground wire to do this...

 

[zanydroid]

This is incorrect...

Ground fault has NOTHING TO DO WITH THE GROUND WIRE...

ground fault devices will trip when there is an imbalance of energy between the conductors.

If more energy is transmitting on the hot wire than is returning on the neutral or other hot wire, the gfci will interrupt the current.

It does not require a ground wire to do this...

I'm not talking about AC GFCI, I agree with what you say for that protection type.

I'm talking about DC ground fault detection. In the ganged breaker config it is done by detecting a low current flow through ground. And this is on the EGC if you look on the schematics. These do not interrupt the fault.

There are probably hall effect DC GFD that do not need EGC but i believe these also cannot interrupt the fault except if they are integrated with RSD. In that case it would help with RSD equipped systems but not say ground mounts

 

[bt77]

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.

Exactly

Correct, same for North America.

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

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.

About utility providing the ground conductor:
What happens if I cancel my utility contract and go completely offgrid replacing my inverter with an offgrid inverter, adding a battery etc.?
So in this scenario, utility is no longer providing me anything, right? I mean literally they will take away the meter, the lines they provide etc.
Now my live and neutral lines are coming from the inverter only. The battery and solar panels are connected to the inverter.
Where do I derive my ground conductor then? Wouldn't that be simply my house grounding grid and all ground lines connect to that grid/rod/plate whatever?

 

[Supervstech]

About utility providing the ground conductor:
What happens if I cancel my utility contract and go completely offgrid replacing my inverter with an offgrid inverter, adding a battery etc.?
So in this scenario, utility is no longer providing me anything, right? I mean literally they will take away the meter, the lines they provide etc.
Now my live and neutral lines are coming from the inverter only. The battery and solar panels are connected to the inverter.
Where do I derive my ground conductor then? Wouldn't that be simply my house grounding grid and all ground lines connect to that grid/rod/plate whatever?

The grounding conductor must be tied to an earthing system, then bonded to the neutral/grounded conductor in ONE, AND ONLY ONE location.
The grounding conductor can connect to as many earthing locations as you like, but the entire system needs to be tied together.

 

[timselectric]

About utility providing the ground conductor:
What happens if I cancel my utility contract and go completely offgrid replacing my inverter with an offgrid inverter, adding a battery etc.?
So in this scenario, utility is no longer providing me anything, right? I mean literally they will take away the meter, the lines they provide etc.
Now my live and neutral lines are coming from the inverter only. The battery and solar panels are connected to the inverter.
Where do I derive my ground conductor then? Wouldn't that be simply my house grounding grid and all ground lines connect to that grid/rod/plate whatever?

The inverter provides the ground. It creates the N/G bond.
Or at least a good unit will.
If not, you must create it yourself.

 

[bt77]

The grounding conductor must be tied to an earthing system, then bonded to the neutral/grounded conductor in ONE, AND ONLY ONE location.
The grounding conductor can connect to as many earthing locations as you like, but the entire system needs to be tied together

The inverter provides the ground. It creates the N/G bond.
Or at least a good unit will.
If not, you must create it yourself.

OK, quoting both your answers:

Say that one and only location where neutral/ground bonding happening is the electrical panel (currently).

When gone offgrid, if inverter will create the bond (say it's a good unit), do I now have 2 locations where the bond is created? Since it needs to be ONE AND ONLY, what do I do? Find the original bond and break it and rely on inverter's new N/G bond? If there is no original bond in the panel and utility was providing the already bonded conductor, then I should be fine, because that will be gone.

 

[timselectric]

OK, quoting both your answers:

Say that one and only location where neutral/ground bonding happening is the electrical panel (currently).

When gone offgrid, if inverter will create the bond (say it's a good unit), do I now have 2 locations where the bond is created? Since it needs to be ONE AND ONLY, what do I do? Find the original bond and break it and rely on inverter's new N/G bond? If there is no original bond in the panel and utility was providing the already bonded conductor, then I should be fine, because that will be gone.

If the unit creates a N/G bond, it also disconnects from the grid. This is usually performed by a common relay, inside the unit.

 

[bt77]

If the unit creates a N/G bond, it also disconnects from the grid. This is usually performed by a common relay, inside the unit.

Yeah but disconnecting from grid doesn't mean anything. In the scenario there is no grid, utility lines gone, just the house wiring remains. I was asking if there is an N/G bond already present in the house panel originally, what happens when the inverter creates a second N/G bond?

@Supervstech was saying there must be ONLY one N/G bond.

 

[timselectric]

Yeah but disconnecting from grid doesn't mean anything. In the scenario there is no grid, utility lines gone, just the house wiring remains. I was asking if there is an N/G bond already present in the house panel originally, what happens when the inverter creates a second N/G bond?

@Supervstech was saying there must be ONLY one N/G bond.

You would remove one of the N/G bonds.

 

[Quattrohead]

Utility are not likely to disconnect the wires physically from your home, they might cut the L1/L2 but their "ground" will still be connected.
If they did totally disconnect all 3 wires (L1/L2/gnd) then your ground will still be connected to your UFER or ground spike, so you will still be grounded.

 

[bt77]

Utility are not likely to disconnect the wires physically from your home, they might cut the L1/L2 but their "ground" will still be connected.
If they did totally disconnect all 3 wires (L1/L2/gnd) then your ground will still be connected to your UFER or ground spike, so you will still be grounded.

Here in Italy you can never be so sure what they will do So I want to be prepared for all options and the worst case of them taking everything away when I decide to go offgrid.

But yeah, I have an earth grid under the house where my grounding lines eventually go. So I guess I will be grounded locally there.

 

[timselectric]

You will still be connected to earth.
But that's not electrical grounding.
Electrical grounding is created by the N/G bond.

 

[Quattrohead]

Ground, Earth, bonding, now you gotta add Italian bureaucracy into the mix too LOL good freaking luck haha

 

[timselectric]

Ground, Earth, bonding, now you gotta add Italian bureaucracy into the mix too LOL good freaking luck haha

Luckily grounding and bonding is universal, all over the world.
Even in Italy. lol

 

[neo2299]

holy moly... 50+ replies... was just wondering if my "grounding" was correct... lol

 

[Marine359]

I’m doing a small 1Kw backup/off-grid roof install. I’m kinda lame, but I don’t see any advantage to grounding the pv. I’m routing each panel through a 30 amp pv breaker. We live in the mountains where we get a lot of electrical storms. Our OTA antennae was a lightning rod, so I took it down because we were getting too many strikes and i had to keep sleuthing and repairing circuits. Had to get rid of satellite dish for the same reason. Cost me big bucks to repair plasma tv and home electronics. since removing antenna and dish, we’ve not had a direct strike in over two years. Putting another lightning rod on our roof in the form of a pv array turns me off. If I ground them, I’m convinced we’ll attract strikes. Isn’t a good breaker setup between pv and controller enough? Heck, my RV has Solar with no path to ground except the frame. Why do I need to ground the panels on my home roof? I’m an off-grid newbie, so I need informed input.

 

[zanydroid]

Grounding is for personnel safety when working on the array. Maybe a hacky non code compliant way to address this is to disconnect the ground when you aren't working on the panels (if you use a switch that switch will not be rated to absorb a lightning strike), or maybe there is a way to preserve the ground fault detection while still having isolation.

Also you have wires up there already for the DC conductors, and the panel only is rated to isolate 1000V from silicon parts to frame. A lightning strike is past that. If it hits the semiconductor parts it will have a path into the house. If it hits a frame it will bust through the insulation between semiconductor and frame. So if you are worried about attracting a strike on the roof then you can't have an unprotected rooftop array.

At minimum you want a surge protection device in the solar setup to eat a glancing blow.

The RV solar frame should also be grounded to the ground fault detector/ to system ground to overcome any induced AC on the frame. It doesn't need to be grounded to the ground obviously since that's exempt in mobile applications.

 

[zanydroid]

Note that a PV breaker or disconnect would not render the array safe from all types of ground faults within the array. Even if you turn off the array there could still be hot PV conductors touching different parts of the PV structural components. You can also forget to disconnect it thinking you are just doing something simple.

And then even with no faults get a shock from induced AC in the frame (happens during normal operation with transformerless inverters)

Even if you open the PV breaker during a storm it is not rated to isolate a direct hit. Better than nothing, sure

Running a EGC from panel to an inverter equipped with ground fault detection can flag some but likely not all possible ground faults.

 

[Pilot Bob]

Your panels are not electrically grounded.
You should erect a fence around them, and place danger signs on the fence.
The panels are electrically connected to the house, through the AIO. That is where your grounding system is.
The grounding system begins and is created by the N/G bond. A ground rod does not ground anything, as far as electrical safety is concerned.
The purpose of a ground rod (for electrical safety), is to connect the earth to your grounding system. To make the earth safe to stand on.
You are relying on 50 meters of earth between the two ground rods to be a fault current path. Earth is not a good conductor.

Lighting protection is a whole different system. And is never in contact with what you want to protect. A Lighting protection system is built above and around what is being protected.

 

[Madcodger]

Well, shoot, now I'm confused... I have an off grid shed with a 120V Victron Multiplus. Outside the shed, I have a ground rod, and the Multiplus is connected to that ground rod at the grounding connection (lower right of unit as I recall).

1) Should I also connect the solar panel frames to THAT SAME ground rod, and to ONLY THAT ground rod? I was going to connect the frames to a separate ground rod, just for lightning/static protection, but now I'm thinking that's a bad idea.

2) Should the SCC be connected to that same ground rod?

3) Should the negative bus bar of the system be connected to that ground rod?

4) Is there anything else in the system that should be connected to that ground rod?

5) I have an AC line (hot, neutral, ground) running from a nearby garage to this off grid shed, connected via an RV outlet to the generator input of the Multiplus. It is not energized unless I specifically want AC power to charge batteries or run things without running down my batteries (i.e., shore power). My assumption has been that the Multiplus is switching the ground from the off grid system to the "shore power" ground when that generator input becomes energized, and then back to the off grid ground when deenergized. Is that correct?

Thanks in advance for clarifications.