12V Off-Grid System - Grounding/Earthing questions please

[GeeGee]

Hi All,

Very first post here...

I just built my first 12V off grid system (I'm not an expert by any means) and have some questions re: grounding / earthing.

Please see attached images for conceptual system diagram of my system, and also a pic of the actual system.

Note: I had the solar guy install my 830W panels (Longi 415w x 2) today (Tue 17-Oct-2023), but I haven't yet connected the solar to my 12V system (as I want to make sure I have the grounding right).

From what I've read, and research done, "the purpose of ground wire is to provide a path back to the source of the electrical current - the main electrical board - in the event of a fault" and "NOT to provide a path to the ground, or to some road buried in the ground".....See image below for where I sourced this information

As such, I intend to ground my system as outlined in my conceptual diagram (see dotted green lines).

My main question therefore is ----------> does this ground wiring look right, is it correct / safe / best-practice?

Kind Regards
GeeGee


PS, yes, I've read that technically you don't need to ground a 12V system, but I don't mind if I do, and I guess I just want to be super safe and also understand how to do it.

PPS, I've read that the grounding wire needs to be one step down from your maximum rated wire (in my case 2/0 AWG), but I've also read that you can get away with 6 AWG. However, if I was to go one-step down, then I very much doubt I could work with 1/0 AWG wire...it would be just too thick to work with (e.g. connecting to the Junction Box, connecting Inverter & MPPT to negative bus bar).

PPPS, as for the concept of grounding, I have a fundamental / silly question ----> in the case of a short circuit, why does the law of physics choose to send the excessive current to the ground path? I mean, what is the rational / theory / physics behind sending excessive current to the ground as opposed to just letting it circulate within the circuit itself (where I'm assuming it would eventually just blow a fuse/circuit breaker)?




12V off-grid system - Conceptual Diagram







12V off-grid system - actual setup




What is the purpose of Ground Wire?
Source: https://www.quora.com/What-is-the-purpose-of-a-ground-wire

 

[Bobert]

Your source for grounding information is relevant to higher voltage ac current. Most of the purpose for grounding is irrelevant to a 12v system. Millions of 12v electrical systems are in use every day that are not earth grounded in automotive and truck applications. Most of these systems employ a chassis ground from the negative side of the battery to the frame. Mostly to use the frame as a conductor although having the chassis ground (not earth grounded) has other advantages also. In these applications earth grounding is not practical and is almost never practiced. If your solar array can produce over 48v you may want to consider earth grounding the frames of the panels if possible however thousands of ungrounded (to earth) mobile solar systems are in use today and I have never heard of a problem except with the higher voltage arrays (300-500 volts) and even in these applications I have not heard of injuries that would have been prevented by earth grounding. I wonder if anyone on this forum has ever heard of such a problem.

Lightning protection is a whole different ball game and I will leave that aspect to someone more experienced with that.

 

[Solarcabin Channel]

Your source for grounding information is relevant to higher voltage ac current. Most of the purpose for grounding is irrelevant to a 12v system. Millions of 12v electrical systems are in use every day that are not earth grounded in automotive and truck applications. Most of these systems employ a chassis ground from the negative side of the battery to the frame. Mostly to use the frame as a conductor although having the chassis ground (not earth grounded) has other advantages also. In these applications earth grounding is not practical and is almost never practiced. If your solar array can produce over 48v you may want to consider earth grounding the frames of the panels if possible however thousands of ungrounded (to earth) mobile solar systems are in use today and I have never heard of a problem except with the higher voltage arrays (300-500 volts) and even in these applications I have not heard of injuries that would have been prevented by earth grounding. I wonder if anyone on this forum has ever heard of such a problem.

Lightning protection is a whole different ball game and I will leave that aspect to someone more experienced with that.

Agreed on the grounding not necessary but just an added safety precaution.

On lightning, it is a myth that solar panels attract lightning and if your house or neighbors houses have never been struck by lightning then adding solar panels won't increase that risk.

That said, if you have tall trees next to your house and panels that can be struck by lightning then you can have indirect flash over that can fry your system.

 

[GeeGee]

Thanks Bobert (and Solarcabin).

FYI, my solar panels are connected in series, so they'll be producing ~70v.

Regarding your statement "If your solar array can produce over 48v you may want to consider earth grounding the frames of the panels if possible" ---> my solar installer has confirmed that he did earth ground the panel frames.

I'm curious, and for arguments sake, if I was to ground my 12v system for added safety, then do my green dotted lines in my conceptual diagram represent best practice grounding?......that is, I run a wire from the Inverter and MPPT Charge Controller casing / frames to the DC negative bus bar, and then run a wire from DC negative bus bar to a grounding earth point?

Regards
GeeGee