Another bl##dy grounding question...

[mr_ed]

Hi All,

I'm designing the earthing and bonding system for my off-grid electrical system and looking for thoughts. I've been through what feels like a million forums etc and found lots of different answers and a general lack of discussion for stand-alone (non-grid tied) off-grid systems.

I've searched this and other forums, been through Mike Holt's grounding videos, read through my local codes (Aus Standards, which appear to have very similar requirements to the NEC), looked at my inverter manual (not much information) and have come up with the attached.

My inverter is separated (AC and DC are electrically isolated) and does not have an internal neutral-to-ground link.

The main thing I'm still scratching my head about is whether to earth my negative battery terminal. I'm still tossing up between the following options (I understand there are also other ways to do it - resistors etc - but I'm trying to keep things simple and cost effective):

1) Bond negative battery terminal to earth as shown with a low current (0.5A) fuse so that if a ground fault occurs I have some indication that it has happened (i.e. a blown fuse). This seems like a fairly common approach but it also promotes some current flow in a ground fault scenario which I don't love.

OR

2) Don't bond battery negative to earth. In this case, under a ground fault scenario you shouldn't get any current flow through the grounding system as there is no return path to the battery, but you also won't have an indication that a ground fault is occurring.

Interested in the brains trusts thoughts on the above and any other thoughts/suggestions on the grounding/earthing design - any input much appreciated!

Cheers.

 

[FilterGuy]

You may want to review this

Ground Fault Protection On Solar Panel Arrays.

To get the paper, click on the orange button at the top of the screen. This paper provides a summary of what a PV ground fault is, what NEC requires for PV Ground Fault Protection and how PV ground Fault Protection is typically implemented...

diysolarforum.com

and at least the first two parts of this series:

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

 

[MisterSandals]

@smoothJoey is a stickler for bonding (hope this does not sound bad):

 

[mr_ed]

Awesome resources thanks @FilterGuy!

 

[RandyP]

You may want to review this
...
and at least the first two parts of this series:

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

Thank you for putting all this info in one place ! AC housing grounding.