Grounding questions - SORRY!

[jodusno.1]

Hello all,
I've read lots of posts about grounding, and have made progress but still a bit confused. I am hoping to add an inverter to my 12v solar off-grid stationary set-up. In the process I realise I might have to re-do my previous grounding - which was simply battery negative to dubious groundrod.
The resources that I found most helpful were Filterguy's grounding resources, and a youtube video by CleversolarbyNick, Reel Clear Media on youtube and the Victron inverter manual. But these don't all seem to agree, which is just maybe how it is with grounding (?).

My questions are:
1) I have a grounding rod, but it is only 1m deep as the ground is pretty rocky and sandy. The internet suggests quite complicated ways to test if this is good enough, but I don't want to spend £100s on a tool I'll only use once. As the ground rod is mainly for discharging static (?) is it terrible if it wouldn't pass a grounding test/isn't a very good earth bond? should I add another dubious rod and connect them? (also considering building a small pond in the vicinity which could drip onto the groundrods - madness?)

2) solarbynick has the grounding rod on the AC side of the system, whereas Filterguy and Victron show it on the DC side. I am hoping this means I can get away with it on the DC side. thoughts? I think the earths are connected anyway inside the Victron 12/375 inverter as shown in Filterguy manual?

3) An important message (from a youtube video by Reel Clear Media 'grounding and bonding part 2) seems to be ONLY ONE Neg-ground bond. But on filterguy's diagrams it looks like there is a connection on the AC side AND on the DC side. Is this that point of disagreement about whether to connect the DC negative to ground? Should I just pick one or other and do it, as it'll probably be fine?

4) I can't find anywhere selling WEEBs in the UK so plan to just ground the PV rails and hope for the best. Sound okay?

5) if anyone can be bothered casting an eye over my new plan and give me a totally subjective thumbs up or down or suggested improvements that would be really kind, thanks. - (especially the bit where I just plan to use a plug-in RCD unit at the AC side of my inverter.)

Thanks in advance for any feedback or suggestions!
I think I'm nearly there..

 

[ricardocello]

Is this in a house or cabin, on a vehicle, or at a campground?

1) I have a grounding rod, but it is only 1m deep as the ground is pretty rocky and sandy. The internet suggests quite complicated ways to test if this is good enough, but I don't want to spend £100s on a tool I'll only use once. As the ground rod is mainly for discharging static (?) is it terrible if it wouldn't pass a grounding test/isn't a very good earth bond? should I add another dubious rod and connect them? (also considering building a small pond in the vicinity which could drip onto the groundrods - madness?)

If this is a permanent installation, I would go with multiple ground rods a few meters apart connected by a single continuous conductor up to the inverter.

I don't know the requirements for the UK, however.

2) solarbynick has the grounding rod on the AC side of the system, whereas Filterguy and Victron show it on the DC side. I am hoping this means I can get away with it on the DC side. thoughts? I think the earths are connected anyway inside the Victron 12/375 inverter as shown in Filterguy manual?

I see no reason to ground a 12 VDC battery on the negative side, unless it is required by code or manufacturer instructions,
or in a vehicle whose frame is bonded to DC negative. Otherwise, it isn't a hazard.

The inverter generates dangerous 230V, so its case should be grounded and connected to the ground rod(s) for your safety.
The neutral-ground bond should also be present in the inverter.

3) An important message (from a youtube video by Reel Clear Media 'grounding and bonding part 2) seems to be ONLY ONE Neg-ground bond. But on filterguy's diagrams it looks like there is a connection on the AC side AND on the DC side. Is this that point of disagreement about whether to connect the DC negative to ground? Should I just pick one or other and do it, as it'll probably be fine?

Only one AC side Neutral-Ground bond. This will prevent objectionable current from flowing in parallel on the ground line.

4) I can't find anywhere selling WEEBs in the UK so plan to just ground the PV rails and hope for the best. Sound okay?

Then use a star washer that digs in or bites into the aluminum to get through the oxidation layer and make a good connection.

5) if anyone can be bothered casting an eye over my new plan and give me a totally subjective thumbs up or down or suggested improvements that would be really kind, thanks. - (especially the bit where I just plan to use a plug-in RCD unit at the AC side of my inverter.)

I'm ok with everything you've drawn except the negative DC grounding, which I find unnecessary.
The RCD at the output is a perfectly reasonable way to use the inverter.
But wouldn't you want a 20A RCBO (residual current operating circuit breaker) to protect against overloads AND residual current?

I have not checked your wire sizing, but presumably you followed the requirements.
Is 6mm^2 adequate for a 40A fused circuit? Seems a little light, consider 10mm^2.

Best of luck.

 

[jodusno.1]

Thank you so much, very helpful. Feel like I'm getting really close now.
(Its a small cabin)

However, I'm still overthinking aspects of this:

1) Why ground rod? At the risk of getting technical information back that is above my braingrade, can anyone explain or point to a resource that shows why this system needs a grounding rod at all? I have watched videos, and they explain about the neutral/ground connection which creates an effective path for electricity to return to source and trip the breakers. There is often a grounding rod in these illustrations but its role in the process is not explained, and then the videos usually go on to talk about all the ways that an grounding rod can introduce problems to your sytem and the ways to mitigate that (connecting them up, other things?). But why not just remove them? Like with vehicle and boat systems? Surely its just as likely that someone can be standing outside their vehicle and create a dangerous fault to ground connnection through their body as it is for me at a cabin - actually probably easier at a vehicle as I would struggle to stand on the ground and reach any electrical component of my set-up (would be standing on my timber porch or timber floor)

I am a total amateur and realise that people spend years studying this stuff to be able to understand it, I just find it hard to do something if I don't feel I kind of understand why I'm doing it.

2) Keep the ground rod seperate? Maybe I could have a grounding rod connection for the PV panels, to reduce static build up (?) and a (futile?) attempt to mitigate lightning effects. But then not connect that system to my DC or AC wiring. Instead just use two neutral/ground connections (one of DC side, one for AC side). like this diagram?

3)The inverter I'm hoping to get is a 375W victron one that comes with a normal wall socket type output. This seems to be inviting people to just plug in appliances, without any breakers. Is there perhaps something internally in the inverter that mitigates some of the risks?

Many thanks to the folks who run and contribute to this forum.

 

[ricardocello]

Thank you so much, very helpful. Feel like I'm getting really close now.
(Its a small cabin)

However, I'm still overthinking aspects of this:

1) Why ground rod? At the risk of getting technical information back that is above my braingrade, can anyone explain or point to a resource that shows why this system needs a grounding rod at all? I have watched videos, and they explain about the neutral/ground connection which creates an effective path for electricity to return to source and trip the breakers. There is often a grounding rod in these illustrations but its role in the process is not explained, and then the videos usually go on to talk about all the ways that an grounding rod can introduce problems to your sytem and the ways to mitigate that (connecting them up, other things?). But why not just remove them? Like with vehicle and boat systems? Surely its just as likely that someone can be standing outside their vehicle and create a dangerous fault to ground connnection through their body as it is for me at a cabin - actually probably easier at a vehicle as I would struggle to stand on the ground and reach any electrical component of my set-up (would be standing on my timber porch or timber floor)

It sounds like you understand the lightning and static discharge purposes for the ground rod (earthing) so I won’t go into that.

The purpose of a ground rod (in the earth) in an electrical system is to bring the relative voltages of all metal enclosures, all devices plugged in, the building, the floor, and the people in it to roughly the same potential. When objects are at the same potential, we say there is 0V between them. When there is 0V between two objects, no current can flow. This makes the electrical system safe. Due to stray AC fields and other static effects which are measurable with a meter, these voltages can get surprisingly large without a proper ground rod.

The main purpose of any grounding system is to provide a return path for fault current.
If a powered device has a safe path back through the ground wire to neutral bond, a breaker will trip indicating a fault, and no current will flow through people. The ground rod isn’t strictly necessary for this function, but adds safety. Example: A live conductor touches a concrete pad. It will likely conduct current to the ground rod and keep the floor from being energized.

Honestly, with such a small setup, you can probably get away without a ground rod.
I say this so others here can argue the contrary position.

I am a total amateur and realise that people spend years studying this stuff to be able to understand it, I just find it hard to do something if I don't feel I kind of understand why I'm doing it.

I totally appreciate that position.

 

[jodusno.1]

Thanks again! very helpful!

 

[Edgenup]

“5) if anyone can be bothered casting an eye over my new plan and give me a totally subjective thumbs up or down or suggested improvements that would be really kind, thanks. - (especially the bit where I just plan to use a plug-in RCD unit at the AC side of my inverter.)“

I have a small off grid system set up in a building in my back yard. 3000 watt inverter, four 12 volt 100ah lifepo4 batteries, six 40 volt 310 watt solar panels. I have two things that run continuously - a plug in cooler that draws about 48 watts and a 48 watt shop light. I do run a 100 watt fan and additional lighting loads of 50-100 watts after sunset. This can drain close to 40% of my battery capacity by sunrise. I operated this without a ground rod for a couple months, but I shut everything down during thunderstorms. IMO your biggest problem is that your AGM batteries are insufficient. AGM batteries will not tolerate very high discharging. A plug in watt meter will allow you to determine exactly how many watts your fan, lights and refrigerator consume. Your diagram shows 3 connections stacked on a positive and a negative battery terminal. It is recommended not to stack more than 2. Have you considered a pair of bus bars here? You do have a ground bus bar. I would suggest connecting your ground rod to the bus bar and running other ground wires to the bus bar. (According to your diagram only your solar panels are connected to the ground rod.) In your circumstances I think I would eliminate the inverter and use those funds to purchase a 12 volt 280 ah lifepo4 battery. In which case you would only need 2 connections to each battery post and could maybe run your fan and refrigerator all night. Also consider that ground rods are sometimes placed horizontally in a trench.

 

[jam_rs]

How did you get this set up in the end? Im essentially running the same setup in a shed but want to make sure its safe to some degree.... and know that a RCD will function.

or