Charge controller, battery & inverter connections

[Mike90250]

That's where my brain fuzzes out and rejects the code we must all follow...

it's not always common sense, to have a ground wire, bringing ligntning into your house panel, inside your wall, and then back out to the ground. But it's code....

[xyxoxy]

I swear I'm not trying to be difficult...

So if I have a separate ground for the PV frames that is unbonded to the ground used for the rest of the system, doesn't that open the door to potential/voltage difference in the 2 grounds?

Since both grounds should be as close as possible to the equipment, I think the furthest I could space 2 ground rods would be 20-25 feet (one on either end of my outbuilding). But if I use 2 bonded grounds for the battery etc. and a third separate ground for the PV frames I'm not sure I can space them far enough apart.

[Mike90250]

Aluminun PV frames need to be grounded by a "certified" connector system, to an un-broken wire, to the ground rod for frames only.

That's my take on it. You need stainless hardware, steel will rot out the aluminun frame via electrolosis.

[xyxoxy]

Just when I thought I had a plan...
I'm still uncertain about how to ground the solar panels. I've honestly been looking at various sites for hours and I can't seem to get a definitive answer to this. Most sites have no real information about this topic other than to stress the importance of proper grounding. Others seem to have conflicting solutions.

You said I need 2 ground rods bonded together below grade with #6 AWG. And I do get why that is. But it also sounds like the metal frames of the solar panel(s) may need to go to a separate ground? Page 30 of the "Suggested Practices" doc you linked to earlier mentions using 2 ground rods but it says that the 2 grounds should NOT be bonded together.

Should the aluminum PV frame go to it's own separate ground or can I run it to a junction box where it uses the same 2 bonded ground rods as the battery and inverter etc? Or are we now talking about 3 ground rods?

This is a small system but a larger one may be in my future and I really want to learn to do this correctly.

[Sunking]

The $20-$30 cost of one more grounding rod (and some sweat) is cheap insurance against frying the whole works or setting my shed on fire.

Only way that can happen is if you panell is struck directly by lightning. Otherwise the ground rods do nothing or have a real purpose. Even with the rods it will still burn down everything.

[xyxoxy]

Nerts!

Well it makes sense though doesn't it?
The $20-$30 cost of one more grounding rod (and some sweat) is cheap insurance against frying the whole works or setting my shed on fire.

Thanks again!

[Sunking]

This is for an outbuilding about 200 ft. from the main house AC service. No connection of any kind to the house and none planned. So I will most likely be driving a new grounding rod at the outbuilding.

No it takes a minimum of two to meet code spaced at least 8 feet apart by code, but best to be 2 x the length they are buried. So if code complinat 8 foot rods, spaced 16 feet apart and bonded together below grade by a # 6 AWG.

[xyxoxy]

This is for an outbuilding about 200 ft. from the main house AC service. No connection of any kind to the house and none planned. So I will most likely be driving a new grounding rod at the outbuilding.

[Sunking]

Do you have a AC service from the utility?

[xyxoxy]

...The more extensive your system is, the more importance is attached to grounding the battery - ( but not to the same point as the solar panel frames)...

Just to clarify, can the ground wire from the panel and the ground wire from the battery both terminate at the same grounding rod as long as I keep them totally separated up to that point (i.e. don't run them to a junction box etc)? I suppose ideally a separate rod would be preferable but is it worth the cost and effort to install 2 of them?

[Sunking]

READING THIS DOCUMENT

Yes Sir that is the one.

[Mike90250]

You know the link to the document that covers it Mike.

READING THIS DOCUMENT

[Sunking]

Grounding a mixed DC and AC system is a "fuzzy" science.

Not really it is quite precise, you just have to know the rules and how to apply them. You know the link to the document that covers it Mike. But I will not answer questions about specific topologies. Not because I am mean, but because DIY do not even know the thousand of other questions they need to ask and know about. Heck I know 10 year veteran electricians who still have to ask questions about it.

[Sunking]

So it looks like that one fuse will cover everything... and I guess there is no real need for a ground wire on my little system?

Completely false statement. Depending on the voltage of the system whether or not the system has to be grounded or not. If the system is below 50 volts there is no requirement to ground anything except framework. If the system is ungrounded only having one fuse will do nothing to protect anything.

[Mike90250]

Well, any panels outdoors, you need a wire to ground the FRAME to "earth".

Follow the INVERTER instructions about grounding it, some are allowed, some will smoke.

The battery - terminal will be called the Common or Return, and should not have a fuse. The more extensive your system is, the more importance is attached to grounding the battery - ( but not to the same point as the solar panel frames)

Grounding a mixed DC and AC system is a "fuzzy" science.