Zwy
Emperor Of Solar
It doesn't matter to me, I won't be having him over for any work.
It doesn't change the fact and yes, it is a fact, that he is incorrect.
What is the simple answer for off grid grounding ?
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It doesn't change the fact and yes, it is a fact, that he is incorrect.
zanydroid
Solar Wizard
If you can get him to write it down in his exact wording then I will consider the experience, but there's too much telephone relaying going on here.
Also, I believe it matters which grounding type the PV side is. There's probably some isolated grounded PV (which no one installs these days) that won't need it.
Zwy
Emperor Of Solar
If the inverter is non isolated, it can have a path for AC to enter PV DC wiring.
This is well known here in these forums.
timselectric
If I can do it, you can do it.
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That's earthed, not grounded.
timselectric
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You said that your electrician told you not to connect the array framework to the grounding system.
Yeah, still the terms tend to confuse me.
My PV array is stand-alone earthed...with the metal combiner box, PV framing and SPDs are grounded to the earthed system (3x8' rods (10' spacing) + 50' of copper wire buried 1').
The AC side of the house system is all grounded, along with all DC equipment, to a earthed system that is 3x8' rods (10' spacing). Yes, the main breaker panel is G/N bonded.
Does that sound even close to using the right terms in the right places?
My post says this...
"I used a 3x8' copper ground system for the house. 6AWG from panel to rod #1, then bonded to each additional rod by 6AWG. Rods are 10' spacing
2 x Arrays (9 PVs each) have their own earth ground. Each panel is connected to 6AWG bare copper then tied to single 6AWG which is then run to array #1, connected the same way. Then on to the 3x8' copper rods spaced 10' foot apart. Each array also had a metal combiner box which is grounded to the same array grounding system."
So the array framework is grounded...but not back to the house ground/earth; the arrays do have a grounding system as described above.
Did I explain that well? I am no electrician to be sure and sometimes get terminology incorrect.
timselectric
If I can do it, you can do it.
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Then, it's not grounded.
The purpose of the electrical grounding system. Is to provide a low impedance (resistance) path, back to the source. So that a breaker or fuse can open (turn off) the circuit. And make it safe, before someone can get hurt.
Earth is not a good conductor.
Your current setup. Requires the fault current (at the array) to travel down the local rod. Through the earth. And up the rod by the house. To get to the N/G bond in the service panel.
This is not a low impedance path. And is unlikely to carry enough current to clear the fault. So the Hazzard will remain until it finds a better path. (Possibly the next human or pet, to visit the area)
Great information and I appreciate your patience.
Here is my question, probably more technical than I can handle...Why does a DC fault at the array require interaction with the N/G at the service panel when there is no direct connection between the DC equipment (array frame) and the N/G in the panel?
In a vehicle a fuse at the battery post will blow when a fault occurs in the wiring. There is no N/G bond there, right? Or am I talking apples & oranges?
Take a lightening strike...it hits the PV frame...wouldn't it travel to the rods in the earth, via the 6AWG ground wire & grounding lugs, and dissipate at that point?
SilverbackMP
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Tangential conversation. I plan on adding some lightning protection to my ground mounts by installing a line of connected lighting rods on poles every 20-25 feet roughly 20 ft in front of the mounts. Same concept as the peak roof line of a building. Plus l have MidNite SPDs on all incoming circuits (AC and DC).
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So, I found this on the IAEI (International Association of Electrical Inspectors) website...
ON THE GROUNDING AND BONDING OF SOLAR PHOTOVOLTAIC SYSTEMS
Fundamentals of Grounding and Bonding
By Joseph A. Kraft / Published in January/February 2021
News & Research / IAEI Magazine / 2021 / 2021 January/February / Features
By Joseph A. Kraft / Published in January/February 2021 Share |
In recent years, products have been developed to comply with the requirements of 690.43 by using the very frames upon which the PV modules are mounted to bond the modules. Many metallic PV racking systems are now listed to UL 2703 to support and bond PV modules. Modern practice requires only an equipment grounding conductor to be run from an array where the modules are so bonded. Where the equipment grounding conductor leaves the vicinity of the array, it is required to be run with the circuit conductors, per 690.43(C), and shall be sized per 250.122. If the equipment grounding conductor is smaller than No. 6 AWG, it is required to be protected from physical damage, per 250.120(C). At one time, the prevailing wisdom required a grounding electrode conductor to be installed from the array to its own grounding electrode or to the premises grounding electrode system. If a separate grounding electrode system for the array was installed, it was required to be bonded to the premises grounding electrode system. While a separate grounding electrode system is still permitted to be installed for a PV array, per 690.47(B), it is no longer required to be bonded to the premises grounding electrode system.
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To me it sounds as if they are saying that if a stand-alone earthing system (properly installed rods and wiring) is allowed and is not required to be connected back to the bonded grounding system at the main panel at the house. Or am I confused still?
Any thoughts?
ON THE GROUNDING AND BONDING OF SOLAR PHOTOVOLTAIC SYSTEMS
Fundamentals of Grounding and Bonding
By Joseph A. Kraft / Published in January/February 2021
News & Research / IAEI Magazine / 2021 / 2021 January/February / Features
ON THE GROUNDING AND BONDING OF SOLAR PHOTOVOLTAIC SYSTEMS
Fundamentals of Grounding and Bonding
By Joseph A. Kraft / Published in January/February 2021 Share |
PV Systems
The Array
A decade ago, it was common practice to bond the metal frames of PV modules by drilling and tapping a hole in the aluminum frame of each module, fastening a lay-in lug to each, and then connecting those lugs with a bare, stranded, copper conductor. Connectors that were made of incorrect materials were sometimes installed, which, owing to their relative position to copper in the galvanic series, would corrode and, eventually, fail. This violated the requirement in Section 110.14 that connectors be identified for the material of the conductor. Another problem was that the surfaces of module frames, being exposed to the elements, would, over time, develop a thin layer of aluminum oxide on their surfaces. This oxide layer was electrically insulative and compromised the conductive integrity of the module/lug connection. Lugs and wire can still be used for bonding PV modules, but the lugs are now required to be listed for the application, per 690.43(A).In recent years, products have been developed to comply with the requirements of 690.43 by using the very frames upon which the PV modules are mounted to bond the modules. Many metallic PV racking systems are now listed to UL 2703 to support and bond PV modules. Modern practice requires only an equipment grounding conductor to be run from an array where the modules are so bonded. Where the equipment grounding conductor leaves the vicinity of the array, it is required to be run with the circuit conductors, per 690.43(C), and shall be sized per 250.122. If the equipment grounding conductor is smaller than No. 6 AWG, it is required to be protected from physical damage, per 250.120(C). At one time, the prevailing wisdom required a grounding electrode conductor to be installed from the array to its own grounding electrode or to the premises grounding electrode system. If a separate grounding electrode system for the array was installed, it was required to be bonded to the premises grounding electrode system. While a separate grounding electrode system is still permitted to be installed for a PV array, per 690.47(B), it is no longer required to be bonded to the premises grounding electrode system.
----------------------------------------------------
To me it sounds as if they are saying that if a stand-alone earthing system (properly installed rods and wiring) is allowed and is not required to be connected back to the bonded grounding system at the main panel at the house. Or am I confused still?
Any thoughts?
cs1234
Solar Wizard
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Do your panels connect in any way (through a solar charge controller) to something connected to your house wiring in anyway? Are you generating any AC with the power collected from your panels? If so, there is a remote chance (in the case of AIO's, a high chance) that AC periodically gets onto the DC solar panel lines. That's why you want to ground the panel frames and racking back to the house N/G bonded system. The AC generated in your house (if it gets onto the solar lines), wants to go back to N/G bond at the house. It does not want to go to a ground rod at the arrays.
timselectric
If I can do it, you can do it.
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It has a negative/ ground bond.
(Battery negative/ vehicle frame)
Lightning wants to go to earth.
Electrical current wants to return to its source.
It's not for a DC fault. (Although it serves this purpose also, if the charge controller has the ability to detect the fault)
It's to protect people from an AC fault, that can find its way to the array framework.
High frequency inverters don't have isolation (a transformer) between the AC and DC systems. Therefore AC voltage is found on the DC wiring. If a panel develops a short. (Usually due to damage or wear)
This AC voltage can be connected to the panel frame.
Also perfectly working panels will induce AC voltage to ungrounded metal frames.
Low frequency inverters do have transformer isolation. But a fault in the inverter can put AC voltage on the DC system.
Proper grounding protects people from all of these situations.
cs1234
Solar Wizard
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No, it is trying to tell you..
If you installed a ground rod at the array (which they don't recommend), it wasn't required. But, if you did.. it's required to be backbonded to the same N/G bonded system that the AC that the solar is generating is connected to.
zanydroid
Solar Wizard
This isn’t an opinion, as the direct AC to solar DC path is visible in the schematic I posted a few messages above.
I didn't read anything about something they "didn't recommend" or "wasn't required".
It stated that it is still permitted...as in it was permitted before.
And I didn't see a single word "backbonded". And it pretty clearly states..." it is no longer required to be bonded to the premises grounding electrode system."
"While a separate grounding electrode system is still permitted to be installed for a PV array, per 690.47(B), it is no longer required to be bonded to the premises grounding electrode system."
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Great explanation, thank you!
The earlier example you gave about completing the circuit through the earth being a bad conductor also really makes it clear.
You do not want to be the low impedance path, haha.
Is there a way to safely test for AC current on the panel frames or mount?
timselectric
If I can do it, you can do it.
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Sometimes you can, and sometimes you can't.
But if it's properly grounded, you can guarantee that it's not.