Ground electrode rods

quique

Hi

I've buried my 5/8" rods into the ground and joined them with a #2 cable using thermoweld.
I'm wondering about bringing my bare copper wire from my panels, down the wall and connecting it to the #2 wire.

Should I also use electroweld or a block terminal?
What about al or cu connectors?

Ethan Brush

quique wrote: »

Hi

I've buried my 5/8" rods into the ground and joined them with a #2 cable using thermoweld.
I'm wondering about bringing my bare copper wire from my panels, down the wall and connecting it to the #2 wire.

Should I also use electroweld or a block terminal?
What about al or cu connectors?

To be NEC compliant, the Grounding electrode conductor must be continuous or irreversibly spliced. It seems you have cad welding capabilities so its no big deal for you, but if you didnt and did not have to comply with the NEC, I would have no problem just split bolting the wires together. The grounding electrode conductor and grounding electrode system is not of paramount importance like the NEC would like us to believe.

Ethan Brush

Is that MEGA MAN? thats one of my favorite games (MM2 actually) from back in the day!

quique

Yeah mega man has always been my favorite.

Yeah I don't need nec compliance but, you mean I would have to bring a copper cable the way from the support mounts down to the ground electrode rods?

That can't be right cause it's impractical to cut a wire the exact size for a run all the way into the ground. Also, a solid ground wire for mounts would need to be 6 or 8 or 10 but ground electrode rods are usually 2 or smaller. A reduction joint would be needed at some point.

Ethan Brush

quique wrote: »

Yeah mega man has always been my favorite.

Yeah I don't need nec compliance but, you mean I would have to bring a copper cable the way from the support mounts down to the ground electrode rods?

That can't be right cause it's impractical to cut a wire the exact size for a run all the way into the ground. Also, a solid ground wire for mounts would need to be 6 or 8 or 10 but ground electrode rods are usually 2 or smaller. A reduction joint would be needed at some point.

I guess I dont follow you. What exactly do you have going on and What are the "mounts"?

I should have mentioned before but the GEC to the ground rods is never required to be bigger than #6 cu

BB.

Just make the 6awg connection to the rod closest to the wall / wire down-drop?

-Bill

Ethan Brush

quique wrote: »

OK I'm trying to ground my panel array. The panels themselves are ground by a #6 wire which rounds down the side of the house. The grounding rods used are 8ftx5/8", 4 of them. Those are bonded together using a #2 stranded copper wire as can be seen in the picture.

My question is, how do I make the connection between my GEC #6 to my #2?

Unfortunately, that question opens a bit of a can of worms. In summary the 2014 NEC requires an "auxiliary electrode" be used to earth the array "as close as practicable" to the location of a roof mounted array. This electrode is not required to be bonded to and made part of the building grounding electrode system as most suitable electrodes are. The controversy is that some industry experts state that having a single earth connection point at a premises is important, otherwise a nearby lightning strike can cause large amount of current to flow through conductors that interconnect the two earthing points since there can be a high potential difference as the lighting dissipates into the earth. These interconnecting conductors will be the equipment grounding conductors and are often run inside the structure, thus a risk of side flash and fire.

Are these electrodes also your "normal" electrical system electrodes? Are you on or off grid?

Personally, I would not run a separate grounding conductor from the array to the electrodes if you do not need 2014 NEC compliance. The Eqiupment grounding conductor run with the array conductors to the charge controller or inverter will do the job fine - just as they do with roof top HVAC units which are used on almost every commercial flat roof.

quique

I'm just queasy about bringing a wire that is lightning prone straight into my inverter. :-(

Mountain Don

When we installed our lightning arrestor system (after being struck by lightning and losing almost every electronic device that was plugged in) we were told to keep the lightning system ground rods and plates separate from the electrical system grounds. So that is what we did.

xsnrg

Mountain Don wrote: »

we were told to keep the lightning system ground rods and plates separate from the electrical system grounds

Paraphrasing: Does this mean the PV frames and mounts (conductive parts) have their own ground rod and conductor, and any equipment that is intended to deliver usable power has it's own ground elsewhere with its own green wire? The only question then would be the outside combiner box... If it were mounted to the array frame or metal pole of a pole mount system, it would bridge the grounds... probably not a good idea. Solved by mounting it conductively distant from the lightning ground stuff? Does my question make sense? It seems to be a point where lighting ground and equipment ground are a grey area.

Ethan Brush

Well lets go through it logically:
1. you need an EGC from the array to the inverter anyway. That is important and required for the GFP in the inverter to function.
2. Lightning wont "choose" the conductor to the ground rod over the EGC to the inverter
3. IF you have a lightning strike you have far worse problems anyway
4. You will still have the insulated conductors directly feeding the inverter, and I dont think lightning will care about that insulation much.
5. Lightning strikes are rare
6. IF you really want or think you need lightning protection, you should consult a standards publication that addresses it such as NFPA 780. An approach that might actually accomplish something would have air terminals ABOVE the equipment you are trying to protect not UNDER them!