off grid setup questions related to grounding and awg

[arnold_ky]

I finally got around to drawing out the diagram based on the recommendations and how it will be laid out on the wall. Let me know if everything looks correct and if the wire sizes appear to be correct. Also if anything else stands out with the updated diagram.

Thanks again for all the help.

elec07.jpg

[mschulz]

I finally got around to drawing out the diagram based on the recommendations and how it will be laid out on the wall. Let me know if everything looks correct and if the wire sizes appear to be correct. Also if anything else stands out with the updated diagram.

Thanks again for all the help.

[ATTACH=CONFIG]5314[/ATTACH]

I am interested to hear from Sunnking or some of the other pros on here why and or if you need two grounding rods.

[sensij]

I am interested to hear from Sunnking or some of the other pros on here why and or if you need two grounding rods.

I would be interested in the opinion of others as well. Without digging too deeply into the drawing, my understanding is that a 2nd electrode is fine if properly bonded to the main electrode, and may avoid some of the splicing complications that could come from using the EGC as the GEC and bringing all grounds to a single AC electrode, or possibly avoids some additional cost of copper / conduit to run a separate GEC to the AC electrode.

[Sunking]

I am interested to hear from Sunnking or some of the other pros on here why and or if you need two grounding rods.

OK unless I am missing something in the drawing, you ground rods do not comply with any electrical codes.

250.58 Common Grounding Electrode


Where a system is connected to a grounding electrode in
or at a building or structure, the same electrode shall be used
to ground conductor enclosures and equipment in or on that
building or structure. Where separate services, feeders, or
branch circuits supply a building and are required to be connected
to a grounding electrode(s), the same grounding
electrode(s) shall be used.


Two or more grounding electrodes that are bonded together
shall be considered as a single grounding electrode system in this sense.

What all that means is you can sink as many ground rods as you want into the dirt, but they must be bonded together to form a common electrode. What I see in your drawing is two isolated ground rods. One rod bonds one enclosure, and the other rod bonds the other enclosure, but there is no bond between them which is extremely dangerous. It is not the 12 volt battery or 120 volt inverter that makes it dangerous, it is mother nature. If lightning were to say strike nearby tree you would have 10's of thousands of volts potential difference between the two systems. If you are any equipment are between those two systems; can you say burnt toast?

The fix is easy. Pound as many rods in the ground as you want into the dirt. Space then at lest 16 feet apart, and run a #6AWG between each of them below earth surface. Keep doing that until you get tired and go broke. When you get done just run a single #6 AWG inside to bond both enclosures. If lightning hits both enclosures will be at the same potential and everyone and everything will be safe.

If it were me, just a single rod as it is cheap, easy, and as effective as 100 rods in your case. Ground does not really do much anything except make things dangerous if done incorrectly. Heck even if done correctly makes a system dangerous if you ground the system. That is why industry and utilities try to avoid grounded systems. They are dangerous and prone to unnecessary outages.

[sensij]

The drawing I am looking at shows a 4 AWG bond between the rods, meeting the code you cited. There may be non-optimal aspects of the schematic, but I don't see anything initially that looks non-code compliant.

[SunEagle]

The drawing I am looking at shows a 4 AWG bond between the rods, meeting the code you cited. There may be non-optimal aspects of the schematic, but I don't see anything initially that looks non-code compliant.

The one thing I would do different would be to instead of running the equipment ground wire from the AC distribution box directly to the ground rod I would run it to the same ground bus for the DC distribution box. Then all of the "equipment boxes" are grounded together. Having ground wires from two different boxes going to the same ground rod could create a potential difference between those boxes should one of those ground wires at the rod get broken.

[arnold_ky]

Sunking, it may not show to much detail on the ground rod, but it should show that the rods are bonded together with the 4 AWG wire. On the ground wire from the AC panel, I was going to put that through an acorn on the first ground rod and then run it over to the other ground rod. Then just terminate the DC ground to the first rod.

[arnold_ky]

The one thing I would do different would be to instead of running the equipment ground wire from the AC distribution box directly to the ground rod I would run it to the same ground bus for the DC distribution box. Then all of the "equipment boxes" are grounded together. Having ground wires from two different boxes going to the same ground rod could create a potential difference between those boxes should one of those ground wires at the rod get broken.

I wasn't sure on this either. I searched quite a bit on the net and found it in a couple places where it was mentioned to terminate the dc ground and the ac ground to the ground rod rather than putting them on the same bus. Let me know if that is correct or if it should be how I have it in the diagram.

Thanks.

[Sunking]

Sunking, it may not show to much detail on the ground rod, but it should show that the rods are bonded together with the 4 AWG wire. On the ground wire from the AC panel, I was going to put that through an acorn on the first ground rod and then run it over to the other ground rod. Then just terminate the DC ground to the first rod.

Well these old eyes don't work like they use to. There is no reason to use two rods or two runs. It will not gain you anything, just cost more.

Like I said pound all the rods you can afford to drive in the dirt. At your voltage and current levels code does not require you to do anything and if you do only requires a #10 AWG. Bond all the rod(s) with #10 AWG running directly beneath the frost line to form a single ground electrode. Then run single 10 AWG inside. Or piss away a lot of work and money your way. I don't care either way, but your way gains nothing.

But FWIW if you want to ground the system a single rod with #10 AWG is more than adequate. If the structure has a real electric service from the POCO, minimum requirement is two rods and a #6 AWG. But understand that is based on a 240 vac 200 amp service. Not a 12 volt battery.

[arnold_ky]

Well these old eyes don't work like they use to. There is no reason to use two rods or two runs. It will not gain you anything, just cost more.

Like I said pound all the rods you can afford to drive in the dirt. At your voltage and current levels code does not require you to do anything and if you do only requires a #10 AWG. Bond all the rod(s) with #10 AWG running directly beneath the frost line to form a single ground electrode. Then run single 10 AWG inside. Or piss away a lot of work and money your way. I don't care either way, but your way gains nothing.

But FWIW if you want to ground the system a single rod with #10 AWG is more than adequate. If the structure has a real electric service from the POCO, minimum requirement is two rods and a #6 AWG. But understand that is based on a 240 vac 200 amp service. Not a 12 volt battery.

Sunking, I appreciate any help or guidance. So are you saying to run the #10 awg ground from the ground rod to either of the panels (dc or ac) and then just make sure the 2 panels connected together? Or are you saying to go away from the DC ground and just run the ground wire from the ground rod to the AC panel?

Thanks.

[Sunking]

Sunking, I appreciate any help or guidance. So are you saying to run the #10 awg ground from the ground rod to either of the panels (dc or ac) and then just make sure the 2 panels connected together?

Yes I think you got it now. Just want to make sure I am clear. One single wire in from the ground rod to bond all equipment enclosures and system if required. You have to understand what I mean by a Grounded System. The equipment needs to be grounded, but not the system. Big difference.

Proper way to run the #10 is directly to the AC panel Ground Buss Bar. Then from that Bus Bar a individual ground wire to each piece of equipment where required. You are using th eAC ground bus as a distribution point in a STAR configuration rather than a Daisy Chain from one to the next in a serial fashion.

Th ebig question i sho ware you doing over current protection on the DC side? Are you using fuses/breakers on each battery polarity or just on one polarity. This is what dictates if the system is Grounded or Floating. If floating you must use fuses on each battery polarity and no ground is needed. If you ground say the negative polarity to make it a Grounded System, then you only put fuses on the hot conductor or positive battery post. Th eonly dangerous wires in your system are the ones connected to the battery post as they are the only conductors that have a high enough energy source connected to them to heat things up. The panel and inverter do not amount to more than a popcorn fart in a hurricane.

[arnold_ky]

Yes I think you got it now. Just want to make sure I am clear. One single wire in from the ground rod to bond all equipment enclosures and system if required. You have to understand what I mean by a Grounded System. The equipment needs to be grounded, but not the system. Big difference.

Proper way to run the #10 is directly to the AC panel Ground Buss Bar. Then from that Bus Bar a individual ground wire to each piece of equipment where required. You are using th eAC ground bus as a distribution point in a STAR configuration rather than a Daisy Chain from one to the next in a serial fashion.

Th ebig question i sho ware you doing over current protection on the DC side? Are you using fuses/breakers on each battery polarity or just on one polarity. This is what dictates if the system is Grounded or Floating. If floating you must use fuses on each battery polarity and no ground is needed. If you ground say the negative polarity to make it a Grounded System, then you only put fuses on the hot conductor or positive battery post. Th eonly dangerous wires in your system are the ones connected to the battery post as they are the only conductors that have a high enough energy source connected to them to heat things up. The panel and inverter do not amount to more than a popcorn fart in a hurricane.

With that said, Since the AC Neutral buss bar and the AC ground buss bar have continuity and I have a 4 awg wire running from the AC ground bus bar. Would I be correct in saying that the AC system is grounded ?


On the DC side, I currently have breakers instead of fuses. I like the idea of breakers as it gives a quick on/off for each of the devices and the batteries.

I am definitely a little more confused with the grounding. One other question with regards to equipment grounding vs system grounding. Would I still apply the logic of the largest ground wire will be the path. So if I used a 6 AWG ground wire from the inverter to the AC panel Ground buss bar, would I need to make sure the wire from the ac panel to the ground rod is 6 AWG or larger?

Thanks.

[arnold_ky]

Here is an updated picture with the changes.

elec08.jpg

[Sunking]

With that said, Since the AC Neutral buss bar and the AC ground buss bar have continuity and I have a 4 awg wire running from the AC ground bus bar. Would I be correct in saying that the AC system is grounded ?

Yes it is, but that is the AC, not DC. If you have that #4 AWG running from th eAc panel to the ground rod, you are done with the Ground Electrode and do not need to add anything more. From the AC ground bus extend, extend a ground to each peice of equipment requiring a ground.


I am definitely a little more confused with the grounding. One other question with regards to equipment grounding vs system grounding. Would I still apply the logic of the largest ground wire will be the path. So if I used a 6 AWG ground wire from the inverter to the AC panel Ground buss bar, would I need to make sure the wire from the ac panel to the ground rod is 6 AWG or larger?[/QUOTE]Not really let me draw something up. You can use as large of a wire as you want, it jus thas to meet minimum size requirements. More in a bit. I do see a problem in your drawing. On your battery you are only showing breakers on the positive polarity, but not on the negative polarity. That means you must run a Ground System and you did not ground your battery Negative post. If you were to have a fault, there is no path back to the source to operate a fuse. That is what I have been trying to tell you all this time. You added over current protection for a grounded System, but left it Floating. You AC side is a Grounded System because you have Neutral and Ground bonded together.

[sensij]

This thread is going sideways fast. The Prostar manual explicitly says the DC side should be grounded, and the negatives (or positives, if positive ground) are all tied together in the controller. Why is this getting hung up on the details of an ungrounded system, when that does not apply in this case?