What is the simple answer for off grid grounding ?

[cs1234]

deleted

 

[cs1234]

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?

Ok. After rereading it. I can see that it is stating you need to ground the panels/racking using an EGC running with the circuit conductors back to where ever they are going (the building) and to be coupled up to that locations grounding electrode system.

If you had a separate ground at the array (which was permitted) it had to be coupled to the main buildings grounding system as well. The change here is that they say it's still permitted to have a separate grounding electrode at the array if you want, but don't couple it up to the building with it's own wire. This DOES NOT say you still shouldn't have the EGC running with the circuit conductors back to the building though.

It looks like they are saying it makes no difference if you run a separate wire back from the separate grounding electrode at the array simply because it's coupled up to the building grounding electrode by the EGC running with the circuit conductors. No point in doing it twice. You've basically just stuck extra metal in the ground for no REQUIRED reason, but it's coupled up to the frames/panels anyway..

 

[Shimmy]

I'd love to see some references for ground loop issue in power wiring (even if it's just EMI/RFI), since I have a really thin bibliography for it.

I worked with a data center that had double-ended substations all over the facility, each side had a dedicated neutral-ground bond. The data center was from the "ground the hell out of it" era. One vendor complained about signal noise on the ground, so we started investigating. You could measure 200A on a raised floor stringer. (Negligible voltage, but negligible ground resistance due to system design.)

They spent several million dollars (due to system complexity) providing a single n-g bond per substation and creating a single reference point for the system.

I had a much less significant issue in another facility where a power feed was inducing 10A of current on a bundle of Cat-5 cables due to insufficient separation. (The bundle was likely 100 cables, so about 0.1A of common mode current.)

I thought the IEEE Green Book was a reasonably good reference as updated, but the older copy I had was terribly out-of-date. (It is a shame the IEEE has let the colored book series age so poorly without updates.)

 

[Shimmy]

@Area 51 Sorry if I missed it, but don't forget about any copper water pipes.

 

[AHTrimble]

If you connect the EGC of the array to the array's ground rod, then it is not an effective ground fault path for either AC fault onto DC conductors (yes, it's possible) nor for DC side ground faults (some DC ground fault detection systems check for a DC current path through the EGC)

I asked Victron about AC being introduced into the DC side of the system. Here is their response...

"Quattro provides galvanic isolation between AC and DC."

So if I am hearing them correctly there would be no AC current backfeeding into the array's DC wiring. Do you read it the same way? You have me concerned and would like to hear your opinion on what this actually means.
Thank you in advance.

 

[Zwy]

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."

A auxiliary ground rod can be installed at the array but it is no longer required to bond it to the premises grounding electrode system. This does not eliminate the requirement to bond the panels and the array to the premises grounding electrode system and running an EGC with the current carrying conductors from the array to the premises grounding electrode system.

Adding an auxiliary ground rod at the array can lead to a voltage gradient from a nearby lightning strike entering the premises grounding electrode system. I would not install one for this reason.

 

[Zwy]

I asked Victron about AC being introduced into the DC side of the system. Here is their response...

"Quattro provides galvanic isolation between AC and DC."

So if I am hearing them correctly there would be no AC current backfeeding into the array's DC wiring. Do you read it the same way? You have me concerned and would like to hear your opinion on what this actually means.
Thank you in advance.

Read this post again: https://diysolarforum.com/threads/what-is-the-simple-answer-for-off-grid-grounding.70317/post-890173

 

[efficientPV]

I bought a house and when working in the basement found this one foot section of copper pipe dangling from a wire. The clamp had a big yellow warning tag that said this clamp should never be removed. Sometimes legal and technical don't intercept.

 

[Bluedog225]

I was encouraged by the thread title ?

Is the simple answer that I should run a grounding conductor from the array racking/panel frames to the main panel and tie it to the single ground for the whole system?

 

[pvgirl]

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).

Lightning protection system has to be bonded to ground system as well:

250.106 Lightning Protection Systems​

​

The lightning protection system ground terminals shall be bonded to the building or structure grounding electrode system.​

​

Also see NFPA 780-2017, Standard for the Installation of Lightning Protection Systems, which contains detailed information on grounding, bonding, and side-flash distance from lightning protection systems.

 

[SilverbackMP]

Lightning protection system has to be bonded to ground system as well:

250.106 Lightning Protection Systems​

​

The lightning protection system ground terminals shall be bonded to the building or structure grounding electrode system.​

​

Also see NFPA 780-2017, Standard for the Installation of Lightning Protection Systems, which contains detailed information on grounding, bonding, and side-flash distance from lightning protection systems.

My arrays are 280 feet away and no way am I gonna send that current to my power shed. And it won’t be attached to shit other than poles. The mounts and panels won’t be connected. Trying to keep any direct strikes from NOT going through them, but hit elsewhere.

 

[AHTrimble]

So here is what Victron had to say...

"Off-grid system grounding
Do not ground the positive or negative of the PV array. The PV negative
input of the MPPT is not isolated from the negative output. Grounding the
PV will therefore result in ground currents. The PV frames however may
be grounded, either close to the PV array or (preferably) to the central
ground."

So if I am reading this correctly...The PV frames can be grounded at the array itself...OR...it can be grounded back at the main panel house ground. And they are recommending it be done back at the house main panel grounding point.

 

[SilverbackMP]

My arrays are 280 feet away and no way am I gonna send that current to my power shed. And it won’t be attached to shit other than poles. The mounts and panels won’t be connected. Trying to keep any direct strikes from NOT going through them, but hit elsewhere.

I might even go with a single one of those ESE rods on a longer pole located a bit further away. If I can ascertain whether or not they are snake oil. And if I can buy or build one that’s not at oil field pricing.

 

[Jim in Florida]

Victron (Tier 1ish) vs white label Chinesium.

My arrays are 280 feet away and no way am I gonna send that current to my power shed. And it won’t be attached to shit other than poles. The mounts and panels won’t be connected. Trying to keep any direct strikes from NOT going through them, but hit elsewhere.

Just curious, I am still pretty new at this.
Without grounding, how do you keep the the extra energy from just using your conductors to go from panels to shed?

 

[Zwy]

So here is what Victron had to say...

"Off-grid system grounding
Do not ground the positive or negative of the PV array. The PV negative
input of the MPPT is not isolated from the negative output. Grounding the
PV will therefore result in ground currents. The PV frames however may
be grounded, either close to the PV array or (preferably) to the central
ground."

So if I am reading this correctly...The PV frames can be grounded at the array itself...OR...it can be grounded back at the main panel house ground. And they are recommending it be done back at the house main panel grounding point.

Victron is not the NEC. Only one requirement and quite simple.

 

[cs1234]

Just curious, I am still pretty new at this.
Without grounding, how do you keep the the extra energy from just using your conductors to go from panels to shed?

The lightning knows that those wires are for PV only, so it doesn't use them.

 

[Shinzul]

The lightning knows that those wires are for PV only, so it doesn't use them.

Lightning is so courteous these days

 

[timselectric]

My arrays are 280 feet away and no way am I gonna send that current to my power shed. And it won’t be attached to shit other than poles. The mounts and panels won’t be connected. Trying to keep any direct strikes from NOT going through them, but hit elsewhere.

I understand your thought process about this.
I would recommend that you make sure that the lighting conductors are not exposed to touching.
As in, placing them in PVC conduit as they run down the pole. For the first 8' above grade.

 

[timselectric]

Just curious, I am still pretty new at this.
Without grounding, how do you keep the the extra energy from just using your conductors to go from panels to shed?

Lighting protection and grounding are two different (separate) things.
He was referring to Lighting protection.

 

[SilverbackMP]

Just curious, I am still pretty new at this.
Without grounding, how do you keep the the extra energy from just using your conductors to go from panels to shed?

Sigh…reread what I said. The lighting protection will be completely separate from the bonded panels with the ground going back to the main. Two different things. The lighting protection won’t even be touching the mounts or panels. It’s job is to try to be a better target so any lighting strikes it rather than the panels.