timselectric
If I can do it, you can do it.
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If you open up your inverter, you'll be voiding your warranty. I would not recommend it, since it's not necessary.
MPP LV6548 Ground/Neutral Safety?
- Thread starter Tetawon
- Start date
Got it. My setup mirrors Will's original Lv6548 240v video, and he has since moved on from the "floating ground" idea. So run earth grounds to the input side of both inverters, then wire the output per the diagram in #60.
timselectric
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Yup
Lt.Dan
Solar Wizard
Mine are not wired like this, mine are wired with both grounds going to my critical loads panel, and yet I don't have any problems. What's the purpose of only one ground? I don't understand.
BuffaloTrace
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Aside from how people are telling one another to use the inverter because of various reasons, I think it is still pertinant to understand all the various ways these inverters can be safely used to power different kinds of bonded or unbonded load panels in either 120 of 120/240 split phase. I really think the overall knowledge base is to grow without writing off other ways of doing things as everyone's use case is different. The main thing is from, function, and safety with manufacturers approval. So far I've been quite enlightened by the various threads and love the different setups. Very versatile
timselectric
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Each inverter creates a n/g bond, when in battery mode. You should only have one n/g bond.
This is to avoid creating a ground loop. This is a safety issue.
eabyrd
Solar Enthusiast
Two grounds to the panel sets up a loop. In all likelihood there will be no real world impact but there is RF impacts
eabyrd
Solar Enthusiast
If both inverters create a neutral-ground bond in battery mode, I believe objectionable current will flow on the EGC (green wire) as shown below. Please let me know if I am missing something. Note that it has not yet been proven that both inverters do create a neutral-ground bond in battery mode in a split-phase configuration. Some people have posted that they do.
Normal neutral current is highlighted in orange. Objectionable current is highlighted in purple. The objectionable current flows to P2's neutral output connection, crosses to the EGC via P2's neutral-ground bond, flows to P1's ground connection, and crosses to P1's neutral output via P1's neutral-ground bond.
If the 120V load is drawing 10 amps, you will see 10 amps on P1's L1, 5 amps on P1's neutral, 5 amps on P2's neutral, and 5 amps on the EGC between P2 and P1. The EGC between P2 and P1 is where you want to measure the objectionable current if you are testing this scenario. Current flow on the EGC is dangerous, so be cautious when testing. The current split may not be exactly half, but I would think it would be close.
The second diagram, created by @FilterGuy, shows the objectionable current flowing though the main panel's ground busbar and also shows the neutral-ground bonds inside of the inverters.
In the diagram below, the purple dashed line is the normal flow and the yellow dashed is the objectionable current.
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timselectric
If I can do it, you can do it.
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Correct
The current will be equally split, if the ground and neutral conductors are the same length and size. If there's a difference in size or length, higher current portion will flow on the easier path.
Easier path = shorter and/or larger diameter.
Objectionable current (current flowing on the green EGC) can kill you.
For example, the neutral to the top inverter is not connected for some reason. Maybe there was a loose connection and it slipped out of the terminal at the inverter or at the panel. Normally, you would notice this because some of your loads would no longer work because they were not receiving power. In the diagram below, those loads would continue to receive power because now all of the neutral current to the top inverter is flowing through the EGC (green wire).
Then you decide to redo the EGC connection. You leave the inverters on because you don't expect the EGC to be carrying current. You remove the EGC from the top inverter and touch the case of the inverter with one hand and the EGC with the other hand. Now 120V is flowing through your heart. Not a good thing. It would also happen if you removed the EGC from the bottom inverter, the panel, etc. Anything that would put you in series with the objectionable current flowing on the EGC.
This one is also very interesting if you have time to watch the entire video.
The diagram below was created by @FilterGuy.
For example, the neutral to the top inverter is not connected for some reason. Maybe there was a loose connection and it slipped out of the terminal at the inverter or at the panel. Normally, you would notice this because some of your loads would no longer work because they were not receiving power. In the diagram below, those loads would continue to receive power because now all of the neutral current to the top inverter is flowing through the EGC (green wire).
Then you decide to redo the EGC connection. You leave the inverters on because you don't expect the EGC to be carrying current. You remove the EGC from the top inverter and touch the case of the inverter with one hand and the EGC with the other hand. Now 120V is flowing through your heart. Not a good thing. It would also happen if you removed the EGC from the bottom inverter, the panel, etc. Anything that would put you in series with the objectionable current flowing on the EGC.
This one is also very interesting if you have time to watch the entire video.
The diagram below was created by @FilterGuy.
eabyrd
Solar Enthusiast
There is no connection between input neutral and output neutral so your loop doesn’t loop. Filter guy’s diagram relates quite rightly to the dangers of running to EGC (grounds) not grounded conductors (neutrals).
The objectionable current in the diagram does not flow on the input neutrals. It crosses to the EGC via the internal output neutral-ground bonds in both inverters (if both inverters bond neutral and ground in battery mode). It is the same flow as the diagram below. I wanted to show that there is objectionable current in the diagram you posted if both inverters bond neutral and ground in battery mode.
timselectric
If I can do it, you can do it.
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Without the neutral passing through. The full current load will travel on the ground conductor. That's even worse, in a ground loop situation.
It's the same thing as having neutral-ground bonds in both the main panel and a subpanel. The two bonds cause current on the EGC. In the diagram below the Service panel is the main panel and the Panelboard is the subpanel
If both inverters create a neutral-ground bond in battery mode, there are multiple neutral-ground bonds in the same system, resulting in current on the EGC. Think of P1 as the main panel and P2 as the subpanel. P1's output neutral is connected to P2's output neutral. Output neutral and ground are bonded in P2 in battery mode via its internal relay. P2's neutral-ground bond allows neutral current to flow to P1 on the EGC along a parallel path just as the neutral-ground bond in the subpanel allows neutral current to flow to the main panel on the EGC along a parallel path.
But it still has not been proven that both inverters do bond the neutral and ground in battery mode. Someone who has two LV6548s paralleled in split phase mode needs to test it.
timselectric
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Correct
I was just pointing out that it's actually worse, if the neutral is not connected. As stated in the post I replied to.
I was just pointing out that it's actually worse, if the neutral is not connected. As stated in the post I replied to.
Definitely. That's what I was talking about in post 71. I probably should not have made my post a reply.
Lt.Dan
Solar Wizard
If you can gimme a break down of how to test it properly, I can test it tomorrow.
Can you post a wiring diagram of the AC part of your system?
Lt.Dan
Solar Wizard
I'm currently on my phone and don't have anyway of making one.
Mine is essentially exactly like the picture on post 60, with the exception of I have the ground wire from both inverters running to my critical loads panel.
