EG4 6500EX off grid install with no Neutral Ground bond.

Supervstech

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Ya, I sketched it out. The N/G bond allows utility power to flow back to the neighborhood transformer which is the source. I was thinking that the transformer neutral was grounded at the transformer, guess it isn't.

Of course then I was unsure as to why the actual ground rod is necessary but that is for lightening.
Actually, the utility transformer IS ground tied, but there are no household disconnects or breakers there, so it is only for atmospheric balancing. The N-G bond needs to be at the panel, so a breaker will trip if any shorts to ground occur.
 

Zwy

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He is not the NEC.
250.30 Grounding Separately Derived Alternating Current Systems (A) (1) System bonding jumper

An unspliced system bonding jumper shall comply with 250.28(A) through (D). This connection shall be made at any single point on the separately derived system from the source to the first system disconnecting means or overcurrent device, or it shall be made at the source of a separately derived system that has no disconnecting means or overcurrent devices, in accordance with 250.30(A)(1)(a) or (A)(1)(b)

Does the inverter have a disconnect or overcurrent device?

Why would an installer not leave N-G bond at the source on a purely off grid system? Certainly would be cheaper to install, plus the installer would not have to be concerned with sizing of the jumper. Third, regardless of whether the inverter has a disconnect means or overcurrent device, the rules are much simpler to follow with N-G bond at the inverter, no determination is needed regarding what is considered disconnect or overcurrent device.

Next, we get into

(2) Supply-Side Bonding Jumper

If the source of a separately derived system and the first disconnecting means are located in separate enclosures, a supply-side bonding jumper shall be installed with the circuit conductors from the source enclosure to the first disconnecting means enclosure. A supply-side bonding jumper shall not be required to be larger than the derived ungrounded conductors.

If you have N-G bond at the first disconnecting means, it requires a system bonding jumper to source. A grounding conductor is not a bonding jumper, don't confuse the two.
 

Zwy

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A main panel has the N/G bonded together, any subsiquent sub panel does not and must be fed with L1, L2, N and G wires.
In your senerio, if the sub panel is going to be your main panel being fed from your inverters with no grid ever again, then N/G need to be bonded in the panel and a local ground rod used.
In can be done that way however a bonding jumper would have to be installed according to NEC 250.30. The EGC is not a bonding jumper and must be sized according to NEC 250.28

If you go to this article from Fluke, you will find the following concerning a SDS system which fully off grid would be according to the NEC definition of a SDS system.

"Proper transformer grounding is critical. Making a grounding connection - typically to building steel, which is required to be bonded to all cold-water pipes - establishes a ground reference. Make proper bonding connections by exothermic weld, not clamps that can loosen over time. Ensure that the high-frequency impedance of the grounding electrode conductor is as low as possible. Wide, flat conductors have less inductive reactance at higher frequencies, and are preferred to round conductors for that reason. The distance between the neutral-ground (N-G) bond at the transformer and the grounding electrode should be as short as possible.

The neutral and ground must be connected to the transformer neutral bus. Making the N-G bond at the main panel is not advised in order to segregate normal return currents from ground currents. The transformer neutral bus is the only point on the system where the neutral and ground should be bonded."

This is due to all electrical current will return to the source. By not having the N-G bond at the source such as first disconnect means in a SDS system, the current in a ground fault situation may not trip the breaker to clear the fault. This is why a bonding jumper is required to be installed from the transformer to the N-G bond located in the first disconnect or overcurrent device if not in the same enclosure.
 

Quattrohead

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In can be done that way however a bonding jumper would have to be installed according to NEC 250.30. The EGC is not a bonding jumper and must be sized according to NEC 250.28

If you go to this article from Fluke, you will find the following concerning a SDS system which fully off grid would be according to the NEC definition of a SDS system.

"Proper transformer grounding is critical. Making a grounding connection - typically to building steel, which is required to be bonded to all cold-water pipes - establishes a ground reference. Make proper bonding connections by exothermic weld, not clamps that can loosen over time. Ensure that the high-frequency impedance of the grounding electrode conductor is as low as possible. Wide, flat conductors have less inductive reactance at higher frequencies, and are preferred to round conductors for that reason. The distance between the neutral-ground (N-G) bond at the transformer and the grounding electrode should be as short as possible.

The neutral and ground must be connected to the transformer neutral bus. Making the N-G bond at the main panel is not advised in order to segregate normal return currents from ground currents. The transformer neutral bus is the only point on the system where the neutral and ground should be bonded."

This is due to all electrical current will return to the source. By not having the N-G bond at the source such as first disconnect means in a SDS system, the current in a ground fault situation may not trip the breaker to clear the fault. This is why a bonding jumper is required to be installed from the transformer to the N-G bond located in the first disconnect or overcurrent device if not in the same enclosure.
Look just quoting random stuff off the interwebs does not make it so.
According to the red text, everyone's home in the USA is wired wrong.

I think your quoted text from Fluke is pertaining to TV/radio/cell transmitter sites where lightning strikes are guaranteed.
 

Supervstech

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Bonding is a complicated scenario for sure…

(1) System Bonding Jumper​


An unspliced system bonding jumper shall comply with 250.28(A)through (D). This connection shall be made at any single point on the separately derived system from the source to the first system disconnecting means or overcurrent device, or it shall be made at the source of a separately derived system that has no disconnecting means or overcurrent devices, in accordance with 250.30(A)(1)(a) or (A)(1)(b). The system bonding jumper shall remain within the enclosure where it originates. If the source is located outside the building or structure supplied, a system bonding jumper shall be installed at the grounding electrode connection in compliance with 250.30(C).
Exception No. 1: For systems installed in accordance with 450.6, a single system bonding jumper connection to the tie point of the grounded circuit conductors from each power source shall be permitted.
Exception No. 2: If a building or structure is supplied by a feeder from an outdoor separately derived system, a system bonding jumper at both the source and the first disconnecting means shall be permitted if doing so does not establish a parallel path for the grounded conductor. If a grounded conductor is used in this manner, it shall not be smaller than the size specified for the system bonding jumper but shall not be required to be larger than the ungrounded conductor(s). For the purposes of this exception, connection through the earth shall not be considered as providing a parallel path.
Exception No. 3: The size of the system bonding jumper for a system that supplies a Class 1, Class 2, or Class 3 circuit, and is derived from a transformer rated not more than 1000 volt-amperes, shall not be smaller than the derived ungrounded conductors and shall not be smaller than 14 AWG copper or 12 AWG aluminum.
(a) Installed at the Source. The system bonding jumper shall connect the grounded conductor to the supply-side bonding jumper and the normally non-current-carrying metal enclosure.
(b) Installed at the First Disconnecting Means. The system bonding jumper shall connect the grounded conductor to the supply-side bonding jumper, the disconnecting means enclosure, and the equipment grounding conductor(s).
Exception: Separately derived systems consisting of multiple sources of the same type that are connected in parallel shall be permitted to have the system bonding jumper installed at the paralleling switchgear, switchboard, or other paralleling connection point instead of at the disconnecting means located at each separate source.
 

Zwy

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Look just quoting random stuff off the interwebs does not make it so.
According to the red text, everyone's home in the USA is wired wrong.

The text provided is from the NEC concerning SDS ( Separately Derived Systems).

It does not pertain to Non SDS systems.

Off grid application is by NEC definition a SDS system as it does not have any input from grid power.


I think your quoted text from Fluke is pertaining to TV/radio/cell transmitter sites where lightning strikes are guaranteed.
It pertains to SDS.

It doesn't matter what the SDS powers, if it is SDS, it falls under 250.30.

Bonding should be done at the source. The requirements for the bonding jumper ensure electricity returns to source in the correct path in a ground fault scenario in order to ensure a breaker will trip.
 
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Quattrohead

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When I do my system on the new house build I will be taking information from professionals and satisfying the AHJ, not some random person on the interwebs.
Good day to you.
 

Zwy

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If the AHJ follows the NEC and you install the system as an SDS, the code under 250.30 applies.

And have a pleasant weekend to you.
 

Sqx2

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I am currently installing a split phase EG4 system in my home, much like the one in the latest Will Prowse video. In his video, he showed how to wire the inverters to a subpanel which was N/G bonded. He recommenced everyone off grid follow his wiring. That is great in all, however 95% of people in an off grid situation would like to use their main or a sub panel which is already existing, because it already has all your loads in the panel. Existing panels are not N/G bonded, correct? The Ground and Neutral are separated, the ground never carries current except in a short. So my question is simple, is it a problem if you wire these inverters to a main or sub panel with the ground connected to earth and the neutral on the neutral bar? Again this is not a UPS, it is strictly off grid. When the power goes out, I throw my main disconnect which isolates me from the grid and I turn on my EG4 split phase system.
Haven't read all responses but normally the first panel from the source is bonded all sub panels neutral and ground are separated.
 

timselectric

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Just for clarification.
A separately derived system is a second power source to a service/or any part of a service.

An off grid cabin is a stand alone system.
And falls under the same rules as any service.
Solar and/or generator have their own rules.
 

Zwy

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Just for clarification.
A separately derived system is a second power source to a service/or any part of a service.


Separately Derived System. An electrical source, other than a service, having no direct connection(s) to circuit conductors of any other electrical source other than those established by grounding and bonding connections. (CMP-5)


Service. The conductors and equipment connecting the serving utility to the wiring system of the premises served. (CMP-10)

An off grid cabin is a stand alone system.
And falls under the same rules as any service.
Solar and/or generator have their own rules.
 

timselectric

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Separately Derived System. An electrical source, other than a service, having no direct connection(s) to circuit conductors of any other electrical source other than those established by grounding and bonding connections. (CMP-5)
Exactly
Connected with the other source by grounding and bonding.
A separately derived system is a second source.


An off grid cabin is a stand alone system.
And falls under the same rules as any service.
Solar and/or generator have their own rules.
 

Zwy

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Exactly
Connected with the other source by grounding and bonding.
A separately derived system is a second source.
I read it as any source other than a service (which in its definition is serving utility) that does not have any direct connection(s) to any other electrical source. It doesn't have to be a second source, I saw no other definition or note where it would have to be a second source. Unless you have a link?

Off grid would fall under this definition (unless you have a link contrary) as it is a source other than a service (serving utility). I looked thru the code under stand alone systems and other sources, no other definition existed that I could find.
 

timselectric

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I read it as any source other than a service (which in its definition is serving utility) that does not have any direct connection(s) to any other electrical source. It doesn't have to be a second source, I saw no other definition or note where it would have to be a second source. Unless you have a link?

Off grid would fall under this definition (unless you have a link contrary) as it is a source other than a service (serving utility). I looked thru the code under stand alone systems and other sources, no other definition existed that I could find.
Sadly I can't provide a source. It's just the knowledge that I pulled from my memory. Working on projects with Engineers and Inspectors. Spending years installing backup generators on schools and other commercial buildings. Not to mention 38 years of code updates classes.
You are certainly welcome to do as you wish with the information.
NEC code is open to interpretation. It all comes down to how you local AHJ interprets it.
 

DanielS

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Grounding is important and systems differ a lot… it’s best if you sketch what you have and how you think you should do it and let everyone chip in their inputs. I wasn’t able to get my head around it till I sketched it out. The inverters create a N-G bond as well so that should be considered in your design.
 

Zwy

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Sadly I can't provide a source. It's just the knowledge that I pulled from my memory. Working on projects with Engineers and Inspectors. Spending years installing backup generators on schools and other commercial buildings. Not to mention 38 years of code updates classes.
You are certainly welcome to do as you wish with the information.
NEC code is open to interpretation. It all comes down to how you local AHJ interprets it.
I ran across this article in ECMag, https://www.ecmag.com/section/codes-standards/grounding-separately-derived-systems-part-1-basics

Then this article in IAEI Magazine (International Association of Electrical Inspectors) https://iaeimagazine.org/2009/november2009/separately-derived-systems/

Both state a totally off grid system is a SDS.
 

Quattrohead

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Shout louder and longer, it still does not make quoting random stuff off the interwebs correct.
You need to get out more.
 

Zwy

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Shout louder and longer, it still does not make quoting random stuff off the interwebs correct.
You need to get out more.
Rather than try to start an argument, it would be more productive to any discussion regarding off grid installations why the NEC considers the installation a SDS and why the bonding jumper is required to the first disconnecting or overcurrent device if N-G bond is in a separate enclosure. The second link explains the reason the NEC requires it.

If you don't have anything technical to bring to the discussion, then it probably would be best to not respond or you should ask questions concerning the technical part of the NEC code and the updates to the code and why these changes were implemented. If you do not have any proficiency or knowledge of the subject it might be to your advantage to research the topic before responding. Putting up posts like the one above provides no benefit to the members here that want to learn about proper bonding and grounding an off grid system and why the NEC definitions and requirements were updated and implemented.
 
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