Ground mount panels grounding questions.
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BentleyJ
Solar Wizard
Panel frames, mounting rails, metalic conduit and J boxes all are grounded to the Green wire which runs all the way back to the main panel and down to the grounding rod.
Depending on distance, it is possible to install a separate grounding rod near the panel array but is not recommended unless there is no alternative.
Depending on distance, it is possible to install a separate grounding rod near the panel array but is not recommended unless there is no alternative.
So it gets grounded to ac side ground? Was not sure if the DC and AC side were completely separated. Thanks for the info.
technically a proper ground isn't "connected" to anything ("ac" side or "dc" side) unless something is failing.
it's linking all of the non connected objects that we touch together so they ideally maintain same balance of static charge. Of course if something fails it also gives a path to hopefully pop a fuse / breaker
it's linking all of the non connected objects that we touch together so they ideally maintain same balance of static charge. Of course if something fails it also gives a path to hopefully pop a fuse / breaker
ScropusGobbleBottom
Corn Pop was a bad dude.
But grounding a dc solar line wouldn't pop any breaker in a short to ground and would leave the metallic conduit energized and then feed that voltage to every grounded object via the bond in the panel, no?
timselectric
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This serves no purpose. As you still need the EGC ran back to the existing grounding system for protection.
And if an auxiliary ground rod (this is what it would be) is installed, it must also be connected to the existing grounding system, to make it also safe.
SunDave
Solar Enthusiast
Hi,
There is a difference between positive/negative wires on the solar panel and ground in this case. The smarter folks could correct me if this is not so.
The grounding discussed here is grounding the panel frames, and anything else metal on the array system.
timselectric
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That would depend on if your equipment includes any DC ground fault detection or protection.
Detection, will notify (display error).
Protection, will shut it down.
If neither exists, then yes, your DC system will be unintentionally bonded on one side. Not necessarily dangerous on its own. Until the other side also shorts to ground.
You are not grounding a DC solar circuit (line).
You are grounding/ bonding anything that can be touched, to make sure it remains safe to touch.
ScropusGobbleBottom
Corn Pop was a bad dude.
I think I worded that wrong, sorry.
Pos of panel shorts to frame, frame is grounded, ground wire takes voltage to the main AC panel, NO breaker (that I have anyway) will trip.
Current will be flowing along frame, other frames, grounding conductor, main panel case, and finally, main panel ground point,
Current doesn't just go on the path of least resistance. If it did, lightning wouldn't look like a spiders web. Some current in this fault could potentially bring pos dc voltage up the netral wires of the house? Small, but still.
I agree, this wouldn't do anything until the second dc conductor made an appearance.
But I could see a major problem in inverters that do not fully isolate ac and dc.
zanydroid
Solar Wizard
It won’t. This is for bonding only.
That voltage will at least also go through GEC to the grounding system, so hopefully that will mitigate the risk of touch safety problems.
(And this bonding is the way NEC wants you to do it anyway)
You likely need a double fault for current to flow.
ScropusGobbleBottom
Corn Pop was a bad dude.
Yup, I know.
And it doesnt seem thoughtful or fruitful. If in fact now in a fault, the entire frame is carrying potential with no breaker. What if the other conductor finds a way to a frame? LOTS of arcs and fire.
zanydroid
Solar Wizard
That’s just the nature of solar. The same thing can happen if you have 1P or 2P strings with no fusing. You will arc but probably not burn outside of the intermittent contact, if the wires have the correct sizing.
Arc faults can hopefully be detected by the detection, I don’t think arc fault detection is required to attempt to isolate the panels (ie by triggering RSD), rather signal to you that there is a problem, by shutting down your production.
If you want solar to be super safe despite infused solar panels doing full blast when in sun you would probably need MLPEs enforcing safety. For instance microinverters to limit the max string voltage, and ground fault detection/arc fault detection on their AC outputs. The microinverters would be able to isolate down to individual panel and de energize trunk circuits if they see a problem
timselectric
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What you have to understand is that there is no fault unless there is a path for current to flow.
Grounding/ bonding provides a path that is preferable to a person becoming the path.
Without equipment that includes either DC fault detection or protection, there isn't a return path to worry about. (Until the second line shorts)
Not a problem for PV, as it's powered limited circuits.
Would be a problem with battery circuits, but that's why we install OCP on battery circuits.
put a breaker on it then
ScropusGobbleBottom
Corn Pop was a bad dude.
How would it trip?
That is my question
Thanks for all the info guy, I will have 6 arrays of 10 panels, each in series, 3 arrays on roofs and 3 arrays on the ground, I have a dedicated solar shed that holds all the solar equipment and batteries. What is the most recommended way to ground all of them? Run a ground from each array back the solar shed and ground them to the AC panel's ground? If so would it be the AC panel from the grid or AC panel after the inverters or both? Should those two ac panels be grounded together as well? I have an electrician who is doing all the grid power/ac stuff before the inverters but I am diying the solar side so still learning. I have done a little bit of electrical, put in sub panels, new breakers etc in the house so know a little but obviously not a lot.
timselectric
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Yes
Connect to your grounding system, at the closest location to the SCC.
Yes
There should only be one grounding system for everything.
Everywhere you run circuit conductors, an EGC should be ran with them.
All EGC's should be bonded (connected) together at every location. Along with all equipment, enclosures, boxes, raceways, and framing.
Can I run the ground from the arrays in the same conduit as the pv wire that goes to the inverters?
zanydroid
Solar Wizard
Yes
I am using 10 gauge pv wire for the arrays, which type and gauge should I be using for the grounding?
timselectric
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Yes, that's how it should be done.
timselectric
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timselectric
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Assuming that your PV panel stickers say 15a maximum fuse size.
EGC should be a minimum of #14 AWG copper.
I would recommend (green) insulated THHN/THWN-2.
EGC should be a minimum of #14 AWG copper.
I would recommend (green) insulated THHN/THWN-2.
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