Inverter earthing (grounding)

[Tired sparky]

Yes ok. I just wanted to know why so many people insist on connecting an earth/ground whatever wire onto their battery bank dc to ac inverter outer metal case. They think it’s protecting them somehow on the ac side but it does nothing on a floating ac supply? Is it to earth the case in the event of a DC positive to case fault? I’m struggling to know why that earthing terminal is even there and the Manuel for my Giandel 24v inverter says in a vehicle to connect it to the negative chassis which I kinda get but in a static setup to to connect it to ground /earth whatever. Why???? What purpose does it serve?

[sdold]

Just to be clear, you're wondering why they connect it to a rod in the dirt, correct?

[J.P.M.]

I had to google the NEC as I had never heard of them! Here in the UK the NEC is the National Exhibition Centre where we go to look at cars, bikes, tool shows etc,. Another term that has two very different meanings lol.

In my opinion("IMO") only, this forum is fortunate to have some technically sophisticated regular posters. However, it is somewhat to mostly dominated by North American input and posters. What that means (also IMO only, and meaning no disrespect), because Americans - but probably not Canadians by the way ("BTW") - can be somewhat parochial and so have a less cosmopolitan outlook than other groups. This can lead to misinterpretations and confusion all the way around.
Like in the real engineering world, a mature outlook, some humility, a sometimes thick skin and an eye to the goal of clear communication helps, particularly and predominantly when and where safety is paramount.

When I designed equipment and systems for non-U.S. applications, besides the usual design philosophy and requirements I tried to bring to my work, I quickly learned to be mindful of culture and terminology differences between nations and sometimes regions within nations (such as China for example), particularly in interpretation of and conformance to national standards of countries foreign to me.

Take what you may want of the above. Scrap the rest.

[Tired sparky]

Just to be clear, you're wondering why they connect it to a rod in the dirt, correct?

Yes or to any earthing point for that matter. In my inverter the metal chassis and the A.C outlet ground pin are connected together. So assuming I get a live-ground fault on an appliance that is plugged into the inverter, where is that fault current going? It’s going nowhere as there is no path back to the secondary winding neutral. For current to flow it needs to come out one side of the winding and go back in the other side. There is no circuit. Grounding the metal inverter chassis does absolutely nothing so why are we told to ground the inverter or risk electric shock?

[sdold]

Here's how it works here in the US with inverters I've used: The power cord on most appliances has three conductors, hot, neutral and ground (earth). The ground conductor is connected to the chassis of the appliance, and at the other end (at the plug) it connects to the ground terminal of the receptacle. If you have a fault in the appliance where the line/hot/live conductor touches the chassis, current flows from the chassis through the ground conductor back to the inverter where it is bonded to neutral, completing the circuit and causing the breaker to open. It works just like the diagrams posted by Sunking. The ground rod isn't part of the fault-clearing process, it's for the other purposes he listed.

Edit: By any chance does your inverter NOT have a ground to neutral bond? I understand your confusion if that's the case, but the only way I can see to allow hot-to-chassis fault clearing is to add that bond. It might be optional if the inverter is meant to feed a service panel as a backup source since the panel already has that bond. My home backup generator is that way (came from the factory without the bond). But all of the 2KW-range inverters I have (Aims and Samlex) have the bond, except for one that came from the factory where they forgot to wire the ground pins at all.