Off-grid ground (earthing)

Callinger

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Oct 2, 2021
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I have spent hours researching this subject and I think I am no closer to answers. One post says: "ground everything metal to earth", another says: "keep everything floating". I just want to keep my equipment and people safe and healthy. I appreciate how complex the topic is:
- off-grid grounding (earthing)
- grid-tie grounding
- mobile installation grounding
- ground-neutral bonding
- A/C side earthing
- PV grounding, bonding, earthing
- lightning mitigation
Many posts and vids give much wisdom and advice but use industry terminology that is over the head of us DIY'ers such as "The only connection made between the ground and the neutral conductor is made on the service side at the meter base."
"English, Spock!"
Perhaps if I can ask one simple question at a time, someone can help us with a few key guidelines / advice.

1. we have an off-grid shipping container based system with 2 LV6548s in parallel to create 240v split phase into to a typical Square-D main panel. to resolve the ground-neutral bond issue should we: a. remove the bar in the main panel between the ground and neutral busses? or b. remove the bonding screw in both LV6548 controllers? c. both d. neither
 

FilterGuy

What, me worry?
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Nov 26, 2019
Messages
5,777
Location
Los Gatos CA
I have spent hours researching this subject and I think I am no closer to answers. One post says: "ground everything metal to earth", another says: "keep everything floating". I just want to keep my equipment and people safe and healthy. I appreciate how complex the topic is:
- off-grid grounding (earthing)
- grid-tie grounding
- mobile installation grounding
- ground-neutral bonding
- A/C side earthing
- PV grounding, bonding, earthing
- lightning mitigation
Many posts and vids give much wisdom and advice but use industry terminology that is over the head of us DIY'ers such as "The only connection made between the ground and the neutral conductor is made on the service side at the meter base."
"English, Spock!"
Perhaps if I can ask one simple question at a time, someone can help us with a few key guidelines / advice.

1. we have an off-grid shipping container based system with 2 LV6548s in parallel to create 240v split phase into to a typical Square-D main panel. to resolve the ground-neutral bond issue should we: a. remove the bar in the main panel between the ground and neutral busses? or b. remove the bonding screw in both LV6548 controllers? c. both d. neither
If you have no grid connection, you have a couple of options:

1654570725772.png
OR

1654570895531.png

If you have the grid feeding the AC input, it would need to be like this:

1654571164161.png

The unconnected grounds at the critical load box are shown to meet the NEC requirement of running the Equipment Grounding Conductor with the Ungrounded (Hot) conductor. However, if they are connected at the critical load box they would form ground loops that could generate significant RFI issues. However, if the inverters are mounted on the metal walls of the shipping container, the loops become unavoidable.

As you point out, there are people that disagree with this, but from my studies and investigations, this is what I believe is the best approach.

The team at EG4 is doing a review of the whole grounding and bonding question with these inverters..... hopefully they will get back to us soon.
 

Callinger

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Oct 2, 2021
Messages
13
This is extremely helpful. THANKYOU!
I assume I need to make sure there is no neutral-ground bond inside the generator?
 

FilterGuy

What, me worry?
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Location
Los Gatos CA
I assume I need to make sure there is no neutral-ground bond inside the generator?
Please review this resource. Particularly pages 12 - 14.

There are many ways to hook things up and have it work correctly. The resource shows a few 240V split phase set-ups with a generator.
 

Callinger

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Oct 2, 2021
Messages
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I opened up one of the LV6548s to remove the N+G bonding screw. Could not find it. Is it allowable to follow this suggestion I found in another thread?:

Simply run grounds to the input side to each inverter so each is properly earthed. Run a single ground from the AC output of 1 (and only 1) of your split-phase units to the panel they service. Just 1. Do not bond at the panel

Simple complete grounding, with no loops and no screws removed
 

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FilterGuy

What, me worry?
Joined
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Messages
5,777
Location
Los Gatos CA
I opened up one of the LV6548s to remove the N+G bonding screw. Could not find it. Is it allowable to follow this suggestion I found in another thread?:
Unfortunately, the screw is under another board. Look at the document I linked to. Toward the end of the document are pictures showing where to find it.

Simply run grounds to the input side to each inverter so each is properly earthed. Run a single ground from the AC output of 1 (and only 1) of your split-phase units to the panel they service. Just 1. Do not bond at the panel

Simple complete grounding, with no loops and no screws removed
That sounds ok for grounding (No ground loops). However, it will end up with two NG-Bonds when on battery.
 

Callinger

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Oct 2, 2021
Messages
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ok. so this upper circuit board must be removed? or can you get to the screw without removing it? I can't work on this till next week.
 

Callinger

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We will make connections as per this diagram:
1654812643975.png


Question: The cases of the 2 controllers are "earth-grounded" (as indicated in the diagram). Is the case of the main distribution panel (breaker-box) also earth-grounded to the same wire? (yes, the N-G bond link has been removed in the breaker box)
 
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