off grid setup questions related to grounding and awg

[Sunking]

OK here you go. Top drawing is a Floating DC System, and the bottom is a Grounded DC System.

GEC = Ground Electrode Conductor. For your application minimum size is 10 AWG but can be as large as you like. I forgot to talk about the panel, but it needs a GEC same size as the one to the AC panel. The GEC is to reference the equipment to earth to minimize touch potential voltages, and provide a path to earth for lightning. Only question I have is does this AC panel connect to the grid, or will it be in the future. If so you will have to use a 6 AWG instead of a #10 AWG

Bonding Jumper is the one that makes the system Grounded or Floating. It shall be the same size or larger as the largest conductor used for Power. So if you wire between the battery and Inverter is #6 AWG, it must be a minimum of a 6 AWG.

DCEGC = DC Equipment Ground Conductor. Must be sized same as power conductors. If the batteries wires from the controller to battery is #12 AWG, the Controller DCEGC must be a minimum #12 AWG. If the Inverter DC power wires is a 6AWG, the Inverter DCEGC must be a minimum #6 AWG.

So if you want to make life easy, you can use #6 AWG for all ground and power wires.



EDIT NOTE: Ignore the Bonding Jumper between the AC Ground Bus and Neutral. It is already there and only shown to drive home that is what makes it a Ground System.

[sensij]

Nice drawings, two comments...

1) In the floating system, the ground wire coming from the panels is an EGC, not GEC.

2) Star topology is superior, but is not required. The GEC's must be unbroken or permanently spliced (among other requirements), the requirements for the EGC's are not as tight.

[arnold_ky]

Thanks again Sunking and sensij. So the only thing I need to add would be run a #6 AWG wire from the negative side of the battery to the ground buss in the AC panel and that will ground the DC side. Sound correct?

On the last picture, should I worry about running a ground wire from the "dc panel box" to the AC ground buss (I have it in the picture, but not sure if it is needed)?

[sensij]

Thanks again Sunking and sensij. So the only thing I need to add would be run a #6 AWG wire from the negative side of the battery to the ground buss in the AC panel and that will ground the DC side. Sound correct?

On the last picture, should I worry about running a ground wire from the "dc panel box" to the AC ground buss (I have it in the picture, but not sure if it is needed)?

The pictures have confused things with respect to grounding. Go back to the basics. Every *component* needs an EGC, which can be tied to the AC ground bus, and can be wired in series or star.

Each *circuit* needs one side bonded to ground. The AC bond is provided through the panel. For higher voltage systems, the DC bond should be normally be an unspliced or permanently spliced connection to the electrode. A single wire can be used as both EGC and GEC if requirements are met. I don't think going into the AC ground bus with a screw down terminal would be OK with a higher voltage system. With a 12 V system, the requirements may not be as tight. I would suggest that if there is ever a possibility of increasing up to a 48 V system at some point, which will have live voltages > 50 V, you might as well wire it correctly now so you only have to deal with swapping components later, and not rewiring.

There is a ton of bad information in this thread along with the good (perhaps in my posts too), but this may be the best you can get for free in a forum like this. If you are still unsure, it wouldn't hurt to spend a little bit and consult with an electrician with experience, if you can find one.

[Sunking]

Nice drawings, two comments...

1) In the floating system, the ground wire coming from the panels is an EGC, not GEC..

Thanks but technically it is neither EGC or GEC. It is a lightning down conductor. It only has one purpose to provide a path for lightning to discharge to earth. EGC do a bit more than that but primarily a planned fault path to operate OCPD, and limit touch potential voltages on any exposed metal like the chassis or raceway. I just dumbed it down for simplification to let the OP know it is not intended to carry any fault current of the system. But basically any conductor that connects to a ground electrode going inside the facility is a Ground Electrode Conductor (GEC) by definition in NEC.

[Sunking]

The pictures have confused things with respect to grounding. Go back to the basics. Every *component* needs an EGC, which can be tied to the AC ground bus, and can be wired in series or star.

Each *circuit* needs one side bonded to ground. The AC bond is provided through the panel. For higher voltage systems, the DC bond should be normally be an unspliced or permanently spliced connection to the electrode. A single wire can be used as both EGC and GEC if requirements are met. I don't think going into the AC ground bus with a screw down terminal would be OK with a higher voltage system. With a 12 V system, the requirements may not be as tight. I would suggest that if there is ever a possibility of increasing up to a 48 V system at some point, which will have live voltages > 50 V, you might as well wire it correctly now so you only have to deal with swapping components later, and not rewiring.

There is a ton of bad information in this thread along with the good (perhaps in my posts too), but this may be the best you can get for free in a forum like this. If you are still unsure, it wouldn't hurt to spend a little bit and consult with an electrician with experience, if you can find one.

Sensi in telecom, data centers, communications facilities and so on basically are connected as I have shown with a couple of tweaks. Typically you would install a ground buss bar on an outside wall where the GEC's enter the building. That buss bar has a few different names depending on its use but Master Ground Bar for all intent and purposes. All the GEC terminate to the bus like Rods, Ring, Building Steel,and UFER in th ecent of the MGB. Adjacent to that is what we call a ACEG which goes to the AC service entrance cabinet to the ACEG ground bus where the Main Bonding Jumper to Neutral buss resides. Then from the MGB are all other required grounds for Battery Plant, Frame Grounds, Signal Reference Ground, etc..

For his application being so small there is no need to have a MGB to bond the two systems. Just use the AC ground buss because there are so few wires required.

[sensij]

Thanks but technically it is neither EGC or GEC. It is a lightning down conductor. It only has one purpose to provide a path for lightning to discharge to earth. EGC do a bit more than that but primarily a planned fault path to operate OCPD, and limit touch potential voltages on any exposed metal like the chassis or raceway. I just dumbed it down for simplification to let the OP know it is not intended to carry any fault current of the system. But basically any conductor that connects to a ground electrode going inside the facility is a Ground Electrode Conductor (GEC) by definition in NEC.

My understanding of 2011 NEC section 690.43, in which Equipment Grounding Conductor is defined in the context of PV systems, is different than yours. I am ok with that. Lightning safety and risk mitigation is a different matter completely, in my opinion.

[Sunking]

On the last picture, should I worry about running a ground wire from the "dc panel box" to the AC ground buss (I have it in the picture, but not sure if it is needed)?

Sorry did not notice a DC Panel Box in your drawing. But yes and it would be the wire I show going to the battery negative term post because I assumed that is where you were going to put the breakers. That is called the bonding jumper. It turns the negative polarity to the same thing as a Neutral in the AC panel. It provides the fault path so the breakers wil operate and make it a GROUNDED SYSTEM. You got to understand what a GROUNDED SYSTEM IS.

[Sunking]

My understanding of 2011 NEC section 690.43, in which Equipment Grounding Conductor is defined in the context of PV systems, is different than yours. I am ok with that. Lightning safety and risk mitigation is a different matter completely, in my opinion.

I am old school, and John Wiles is still taking a lot of heat calling it a EBC. 2015 cycle will all change that. FWIW there is no such thing as an EGC anymore. It is called Equipment Bonding Conductor. Ground is only used with a conductor that goes to dirt or a body in place of dirt. About the only conductor that wil have ground in its name is the GEC and that is it. Nothing else will be called Ground. Well except a GROUND SYSTEM which I am trying to make the OP understand the difference between a Floating System and Grounded System. I don't think he gets it yet and is a deadly misunderstanding.

Here is where John is taking a lot of heat and lost the argument. The panels are bonded for the primary purpose of lightning protection. Anyone who designs lightning protection systems uses NFPA 780, not 73. Last thing you would ever do is route Down Conductors with equipment conductors and no idiot would route them through equipment. You do the exact opposite and route or shunt them away from equipment and the building giving them a direct route straight to Mother Earth. I have no idea how John got away with that. Mike Holt busted his and code panel balls over that. That will change in th enext code cycle now that it has attention being focused on it.

John was trying to save solar customers money by taking short cuts to promote the industry. He got away with it for a while as Political Correctness derailed safe practice.That is coming to an end

[sensij]

Sensi in telecom, data centers, communications facilities and so on basically are connected as I have shown with a couple of tweaks. Typically you would install a ground buss bar on an outside wall where the GEC's enter the building. That buss bar has a few different names depending on its use but Master Ground Bar for all intent and purposes. All the GEC terminate to the bus like Rods, Ring, Building Steel,and UFER in th ecent of the MGB. Adjacent to that is what we call a ACEG which goes to the AC service entrance cabinet to the ACEG ground bus where the Main Bonding Jumper to Neutral buss resides. Then from the MGB are all other required grounds for Battery Plant, Frame Grounds, Signal Reference Ground, etc..

For his application being so small there is no need to have a MGB to bond the two systems. Just use the AC ground buss because there are so few wires required.

Yes, what I wrote is misleading. At least from 2011 forward, the ground bar in the panel is OK as long as the bond is made properly.

Thanks for the preview of the next cycle, I am glad CA tends to be a cycle behind, giving some time for the interpretation to become clear.

[Sunking]

Yes, what I wrote is misleading. At least from 2011 forward, the ground bar in the panel is OK as long as the bond is made properly.

Thanks for the preview of the next cycle, I am glad CA tends to be a cycle behind, giving some time for the interpretation to become clear.

Some states are still 2002. Much of what has came out since is manufacture driven like AFCI breakers which significantly raise installation cost. But you were right there different aspects to grounding and is why I avoid discussing it here. It is to complicated and way beyond the scope of a DIY forum. I am one of the moderators on Mike Holt Code Forun which is for professionals only and even experienced EC can't get their head wrapped around it. To the aspect there are 4 sub categories. 1 is the NEC which is the minimum safety category what electricians are suppose to know, Lightning Protection which is NFPA 780 and UL Master Label, Performance or Sensitive Electronic side, and lastly the Protection side of TVSS.

As you can se something so simple as this system got complicated because every little thing had to be explained and detailed out. IT scares me because I really do not want to see anyone get hurt. So I usually stay out of it so I can not be held liable.

[arnold_ky]

Some states are still 2002. Much of what has came out since is manufacture driven like AFCI breakers which significantly raise installation cost. But you were right there different aspects to grounding and is why I avoid discussing it here. It is to complicated and way beyond the scope of a DIY forum. I am one of the moderators on Mike Holt Code Forun which is for professionals only and even experienced EC can't get their head wrapped around it. To the aspect there are 4 sub categories. 1 is the NEC which is the minimum safety category what electricians are suppose to know, Lightning Protection which is NFPA 780 and UL Master Label, Performance or Sensitive Electronic side, and lastly the Protection side of TVSS.

As you can se something so simple as this system got complicated because every little thing had to be explained and detailed out. IT scares me because I really do not want to see anyone get hurt. So I usually stay out of it so I can not be held liable.

Sunking, no need to worry. You won't be liable for anything. I will think this through one more time and make some modifications to the design.

Thanks

[Sunking]

Sunking, no need to worry. You won't be liable for anything. I will think this through one more time and make some modifications to the design.

Thanks

You are welcome and I think we have it worked out. Your last question was a good question and indicates you are getting it.

You last drawing is telling me you are running a Grounded System, but you never grounded the system, you grounded the equipment, but not the system. The give away is you only provided OCPD on the Positive polarity of the battery bu tleft the Negative Floating, thus no path for a fualt to return to its source which is the battery. Go back to my last drawing and notice the difference between Floating and a Ground System. The Floating system uses OCPD on both battery polarities. The Grounded System only uses OCPD on the positive polarity, and has the negative bonded to ground via the added Bonding Jumper which makes it a Grounded System. That Bonding Jumper provides the planned path back to the source of power the battery. It completes the circuit.

[J.P.M.]

Sunking, no need to worry. You won't be liable for anything. I will think this through one more time and make some modifications to the design.

Thanks

P.E.'s tend to worry about those things more, even if not stated explicitly, or all the time. Such concern is usually based on sound logic and experience, and one of the reasons they are called Professional. Also one more reason why P.E's make the big bucks - you want nice, you pay nice. In addition, those big bucks are necessary and helpful w/ the professional liability insurance premiums.

[bcroe]

I am old school, and John Wiles is still taking a lot of heat calling it a EBC. 2015 cycle will all change that. FWIW there is no such thing as an EGC anymore. It is called Equipment Bonding Conductor. Ground is only used with a conductor that goes to dirt or a body in place of dirt. About the only conductor that wil have ground in its name is the GEC and that is it. Nothing else will be called Ground. Well except a GROUND SYSTEM which I am trying to make the OP understand the difference between a Floating System and Grounded System. I don't think he gets it yet and is a deadly misunderstanding.

Here is where John is taking a lot of heat and lost the argument. The panels are bonded for the primary purpose of lightning protection. Anyone who designs lightning protection systems uses NFPA 780, not 73. Last thing you would ever do is route Down Conductors with equipment conductors and no idiot would route them through equipment. You do the exact opposite and route or shunt them away from equipment and the building giving them a direct route straight to Mother Earth. I have no idea how John got away with that. Mike Holt busted his and code panel balls over that. That will change in th enext code cycle now that it has attention being focused on it.

So we have the Equipment Bonding Conductor to protect personal from system faults, and
Down Conductors to protect the system from lightning? That seems to be the organization
here. A continuous 6 gauge connects all exposed frames to the central ground point. But
that is laid out over nearly 500'. For lightning, there are also 59 independent short connections
spread among the equipment, directly to the ground below. These connections aren't
necessarily low enough resistance to protect anybody. Bruce Roe