DC Ground Rod/Grounding Electrode

RandyP

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My inverter is ............ The manual shows this ground being connected to the battery enclosure - and also indicates that it must be bonded to the ground rod with wire that is as large as the largest DC wire.

............
Could you post the pages from the manual that state this ?
 

Netsua

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Does "Method 1", the pic on the right look like a "ground loop"?
Does seem like the potential is there. But my understanding is that since a 48v system doesn’t qualify as low voltage, there are only so many options.
 

WYtreasure

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Does seem like the potential is there. But my understanding is that since a 48v system doesn’t qualify as low voltage, there are only so many options.
I've been in search of proper grounding of my 24 volt system (still to be assembled) for quite some time now. Some say this, some say that.

The only thing I have to offer is I would not do that. Maybe when I am smarter I will but not with what I know today.
Edit for clarification: "I would not do that" in reference to "Method 1", the pic on the right in post 42.
 
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RandyP

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Thanks. Looks like Magnum Inverter equipment.
Just note that the manual uses the GE term, meaning "Grounding Electrode", not 'ground rod". In a vehicle the chassis is the Grounding Electrode, GE.
 

RandyP

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Here's a page from a 2020 Sensata (Magnum) inverter manual on system grounding.
The last paragraph above the sketch talks about system grounding of two isolated systems, the required System Bonding jumper in each system and the two grounding electrode conductors at one Grounding Electrode attachment point is shown on the sketch. The text infers that this method does not create any grounding loops, because the AC system is isolated from the DC system by a transformer:
1642829758808.png
 
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Zil

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250.166
(A) Not Smaller Than the Neutral Conductor

Where the dc system consists of a 3-wire balancer set or a balancer winding with overcurrent protection as provided in 445.12(D), the grounding electrode conductor shall not be smaller than the neutral conductor and not smaller than 8 AWG copper or 6 AWG aluminum.

(B) Not Smaller Than the Largest Conductor

Where the dc system is other than as in 250.166(A), the grounding electrode conductor shall not be smaller than the largest conductor supplied by the system (both AC and DC), and not smaller than 8 AWG copper or 6 AWG aluminum.

***ABOVE - Here's your code. We can all post analogies all day long, but at the end of the day, the answer to your question is "because the code requires it." If you consider your skill set to be beyond the reproach of the NEC, I wish you the best.
I don't think this is applicable to the OP.
 

Netsua

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Here's a page from a 2020 Sensata (Magnum) inverter manual on system grounding.
The last paragraph above the sketch talks about system grounding of two isolated systems, the required System Bonding jumper in each system and the two grounding electrode conductors at one Grounding Electrode attachment point is shown on the sketch. The text infers that this method does not create any grounding loops, because the AC system is isolated from the DC system by a transformer:
View attachment 80746
Yes, this picture is the exact same as the first picture I posted entitled “Method 2”. But as also mentioned on that page, it requires the GEC be no smaller than the largest conductor in the DC system. Which in my system would be 4/0 at almost 40 feet.

I only came back to this thread to share the solution in case someone encounters it in the future. My experience is not theory. It is built, finished, operational, code compliant and has passed inspection.

When I encounter this situation again in the future, even if the system is 24v, I will do it the same way. I’m not interested in debate on whether or not code would require this method in a 24v system. However I do know that code requires it here for a 48v system.

In short - Future internet user that stumbles upon this thread: If you’re building a 48v system and your AC and DC panels are far enough away from each other that that the methods proposed in the Magnum manual are cost prohibitive, please see the photo I attached mid thread for a solution that is both code compliant and doesn’t require excessively long lengths of extremely heavy gauge wire. Best of luck.
 

WYtreasure

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Yes, this picture is the exact same as the first picture I posted entitled “Method 2”. But as also mentioned on that page, it requires the GEC be no smaller than the largest conductor in the DC system. Which in my system would be 4/0 at almost 40 feet.

I only came back to this thread to share the solution in case someone encounters it in the future. My experience is not theory. It is built, finished, operational, code compliant and has passed inspection.

When I encounter this situation again in the future, even if the system is 24v, I will do it the same way. I’m not interested in debate on whether or not code would require this method in a 24v system. However I do know that code requires it here for a 48v system.

In short - Future internet user that stumbles upon this thread: If you’re building a 48v system and your AC and DC panels are far enough away from each other that that the methods proposed in the Magnum manual are cost prohibitive, please see the photo I attached mid thread for a solution that is both code compliant and doesn’t require excessively long lengths of extremely heavy gauge wire. Best of luck.
Thank you very much for answering my questions.

I for one appreciate you taking the time to share. (y)(y)
 

RandyP

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Sorry guys, haven't been keeping an eye on this lately and missed the responses. I did finally make a decision - which I believe was the correct one.
I ran a short 4/0 wire to a smaller bus bar - which is where I ran all my DC grounds. I then ran that to the System Bonding Jumper in the primary AC service panel. I ran my ground rod from that point also - on the AC side.
View attachment 79666
This is the solution and sketch you are referring to. Looks good to me. Thanks for straightening this out.
 

nestyplus

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Just asking, is it alright to install a grounding rod just near the wall of my house?
 

12VoltInstalls

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Just asking, is it alright to install a grounding rod just near the wall of my house?
Depends on your equipment and configuration. For a typical grid entrance that’s normal.
For many of the applications discussed here it would most likely be incorrect, but could be correct depending on your equipment and configuration.

There’s not a binary answer without context
 

AdmrLechuza

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Grounding is a multifaceted beast, and has many different implication as whether it is AC or DC and/or even RF. An electrical diagram will show many items tied to ground rather than draw out the wiring for a ground wiring path. In AC circuits it typically refers as a chassis ground to bleed of static and provide a path of least resistance when/if the device has a short.

When we get to Inverters and especially the All-in-one units, it is recommended we treat them as a sub-panel. This Video shows the wiring and use of the sub-panel giving detail for ground and neutral connections. The ground wire is to provide a chassis ground to the cabinet of the invertor. When the AC loads are connected to the Inverter with a sub-panel the ground is still for Static and Chassis connections and not a current wire, the sub-panel passes the ground back to the main service panel and connects to earth with its bonding. The bonding of the main panel to earth is primarily to prevent lightning entry.

When you connect your batteries to your invertor they are completely isolated from all AC connections and bonding. On your Battery you can have a Negative Buss Bar to connect all the DC negative connections together. Never connect the batteries to earth ground, should the invertor generate a short you could send AC through the batteries and have an explosion.

Off-grid systems are wired with a sub-panel also, but as it does not have a main panel with a ground bonded to create the static/chassis connection we need to connect this panel to a ground rod to give that static/chassis connection. We DO NOT bond this panel! Again the Ground and Neutral in this sub-panel are NOT connected. Your Neutral wire is a current carrying wire to complete the circuit, the ground is for Static/Chassis and helps the circuit trip when there is a fault.
 

timselectric

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If the battery case is metal. Connect it to the ac grounding system. Which means any grounding point of the system. I don't ground the DC negative. Or the positive for that matter. Only any metal enclosures that has power in it. Whether it's dc or ac. If dc positive and negative find a way to meet each other that's a bad day. I'm not going to bond the negative and increase the chances by 50%.
 

12VoltInstalls

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Off-grid systems are wired with a sub-panel also, but as it does not have a main panel with a ground bonded to create the static/chassis connection we need to connect this panel to a ground rod to give that static/chassis connection. We DO NOT bond this panel! Again the Ground and Neutral in this sub-panel are NOT connected. Your Neutral wire is a current carrying wire to complete the circuit, the ground is for Static/Chassis and helps the circuit trip when there is a fault.

N-G bond has to be somewhere. Or it can’t “help the circuit trip when there is a fault.” In fact the bare/ground isn’t a helper- tripping the breaker is its primary function.

Depending on the installation and equipment what you described might even be dangerous.
 

timselectric

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In any ac system (in the US) , the n/g bond is required at or before the first means of disconnect. And after that first means of disconnect, the neutral and ground are kept separate. It's not a neutral, unless it's bonded to ground. ( Neutral = Grounded conductor)
Otherwise, it's just another hot.
 

RandyP

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Chew on this, and when/if you digest it, you will understand much more about grounding and grounding terminology.
There is a paper on mobile grounding also (solar and DC systems).
 

nestyplus

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Hello Guys, just a quick question... I'm wiring my grounding wire at the rails in my house roof along with the solar pv dc wires. I will not place a combiner box.
My question is: Can I combine these three wires (grounding wire, pv+ wire, pv- wires) in one conduit going down to my electrical panel?
Or would you advise to separate the grounding wire in another conduit? thank you
 
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