LV 6548's Split phase = Not Awesome

[RGH69]

Here is a better depiction of my current setup.

 

[Zwy]

You are correct, I never removed any screws from the LV6548's so I assume they still had the NG bond.

Both main panel and subpanel have a N-G bond?

 

[RGH69]

Both main panel and subpanel have a N-G bond?

No neutral to ground bond in the subpanel.

 

[Zwy]

After reading a lot of this forum you'll get of feel of which ones to skip, sometimes even put on ignore. Arrogance, rather than avuncular behavior, abounds in some.

If you are referring to me, you will have to try much harder next time to offend me, I've certainly been called much worse.

But if you have true values in life, (integrity, honesty, courage, commitment), it doesn't matter what we might disagree about as I will stand with you 100%.

Anyone who knew me personally knew where I stood and notice I said with you, and not behind you. Even though many cussed me (relatives, subordinates, superiors, employees, neighbors and friends) they still respected me and I respected them.

My whole life I've been called worse than what you can put forth. My mother says when I was born, the doctors and nurses all cussed when I came out saying what a little &^%$#!#$%^&&&**((&*^%^%$$##@$%^$&&*8 you have and she agreed with them.

 

[Zwy]

No neutral to ground bond in the subpanel.

In another thread, I posted what I theorize what might have occurred, some may disagree but with multiple N-G grounds it creates a situation where there can be voltage where it should be zero reference on a circuit board. https://diysolarforum.com/threads/n...t-without-the-bonding-screw.53547/post-723147

Regardless, you have multiple N-G bonds in your system. This needs to be corrected not only from a safety issue but also one where electronics can be damaged. This can be accomplished several ways. Removal of the common neutral and relying on the neutral switching of the inverter transfer switches. Or installation of a 3 pole double throw transfer switch such as shown in this post. https://diysolarforum.com/threads/lv-6548s-split-phase-not-awesome.54708/post-722915

Some will claim the common neutral is acceptable as the EG4 6500EX is now using a pass thru neutral for stationary applications. However, I have not seen any firmware updates for the MPP LV6548 that would allow this and would disable the N-G grounding relay internal to the units. If you are still inclined to experiment (as it is not supported) and use a common neutral, then removal of both bond screws will be necessary.

My personal system utilizes the 3 pole double throw transfer switch to allow complete bypass of the inverters. This is my preferred installation as it not only solves the N-G bonding issue but also allows complete isolation of the inverters for repairs, maintenance and other reasons.

 

[zanydroid]

Perhaps, but what harm does "objectionable current" cause?

I doubt it can kill an inverter, but it raises the risk of:
- grounded chassis being raised above 0V relative to earth
- EGC carrying current in excess of what they are specced for. In the US, one EGC can be shared across many circuits, and below #10 are smaller than the current carrying conductors they protect.

 

[RGH69]

In another thread, I posted what I theorize what might have occurred, some may disagree but with multiple N-G grounds it creates a situation where there can be voltage where it should be zero reference on a circuit board. https://diysolarforum.com/threads/n...t-without-the-bonding-screw.53547/post-723147

Regardless, you have multiple N-G bonds in your system. This needs to be corrected not only from a safety issue but also one where electronics can be damaged. This can be accomplished several ways. Removal of the common neutral and relying on the neutral switching of the inverter transfer switches. Or installation of a 3 pole double throw transfer switch such as shown in this post. https://diysolarforum.com/threads/lv-6548s-split-phase-not-awesome.54708/post-722915

Some will claim the common neutral is acceptable as the EG4 6500EX is now using a pass thru neutral for stationary applications. However, I have not seen any firmware updates for the MPP LV6548 that would allow this and would disable the N-G grounding relay internal to the units. If you are still inclined to experiment (as it is not supported) and use a common neutral, then removal of both bond screws will be necessary.

My personal system utilizes the 3 pole double throw transfer switch to allow complete bypass of the inverters. This is my preferred installation as it not only solves the N-G bonding issue but also allows complete isolation of the inverters for repairs, maintenance and other reasons.

Well, the interconnect lockout is $25 vs a 3pole double throw being $700 for 60amp and way, way higher for anything more. The main reason that I wanted to keep the Neutral connected between the main and the sub is so I can switch back to the grid feed to sub if I needed to. However, if the EG4 6500ex's have a pass through Neutral then that should also work for the grid feed to the sub (back via the 6500) even if the inverter is shut down, correct?

 

[Zwy]

Well, the interconnect lockout is $25 vs a 3pole double throw being $700 for 60amp and way, way higher for anything more.

I have a 100A sourced off ebay for $700 and I have a 60A that purchased for $450. I prefer the 100A.

The main reason that I wanted to keep the Neutral connected between the main and the sub is so I can switch back to the grid feed to sub if I needed to.

I understand. However there are always trade offs when attempting to economize. Safety is the most important and should not be compromised.

However, if the EG4 6500ex's have a pass through Neutral then that should also work for the grid feed to the sub (back via the 6500) even if the inverter is shut down, correct?

It should, it requires the latest firmware and no bonding screw present. This is supported by Signature Solar.

On the safety side, if you wish to work on your system for various reasons that involves removing the inverter front cover or anything with AC power, you will have to shut your whole subpanel down and turn off the breaker at the main panel. You could work on the batteries, that is about it. The only loads you can power are those on the main panel except power to the inverters.

 

[RGH69]

Okay, I will remove the neutral bond between the main and sub when I get the 6500's.
Thanks!

 

[Zwy]

Here is a better depiction of my current setup.
View attachment 137848

How is your PV combined? I looked up your panels and with the bi facial gain, it comes to a max of 15.16A per string of 4. If you combine 2 strings, you could see as high as 30A into one SCC. I noticed the diagram is missing one PV lead to inverter P1, but your photo shows both positive and negative leads.

How cold does it get in your area?

 

[RGH69]

I will say that I don't blame Ian, he has been supportive through the process. Mpp Solar has been difficult for the most part. However, when I ordered 2 main boards for them, they got it to me in a couple of days direct from Taiwan. Perhaps the neutral bonding between the breaker panels or the ground-neutral bonds in the inverters themselves. I am not certain what the original issue was that started this chain of events but I am moving forward with a different inverter setup.

How is your PV combined? I looked up your panels and with the bi facial gain, it comes to a max of 15.16A per string of 4. If you combine 2 strings, you could see as high as 30A into one SCC. I noticed the diagram is missing one PV lead to inverter P1, but your photo shows both positive and negative leads.

How cold does it get in your area?

it’s not missing, I just have 3 strings of 4. Nothing parallel. That is why there is only one input to SP1. I am near Houston, Texas.

 

[Gavin Stone]

I will say that I don't blame Ian, he has been supportive through the process. Mpp Solar has been difficult for the most part. However, when I ordered 2 main boards for them, they got it to me in a couple of days direct from Taiwan. Perhaps the neutral bonding between the breaker panels or the ground-neutral bonds in the inverters themselves. I am not certain what the original issue was that started this chain of events but I am moving forward with a different inverter setup.

I saw you mention the eg46500 as a possible alternative. Keep in mind, if this isn’t a neutral ground bonding issue. Which again, I don’t believe it caused this. Then those inverters will be wired the exact same way as far as output and input. And you’ll likely have another issue if problem is on the ac side of things.

 

[EastTexCowboy]

I will say that I don't blame Ian, he has been supportive through the process. Mpp Solar has been difficult for the most part. However, when I ordered 2 main boards for them, they got it to me in a couple of days direct from Taiwan. Perhaps the neutral bonding between the breaker panels or the ground-neutral bonds in the inverters themselves. I am not certain what the original issue was that started this chain of events but I am moving forward with a different inverter setup.

it’s not missing, I just have 3 strings of 4. Nothing parallel. That is why there is only one input to SP1. I am near Houston, Texas.

I'm not too far away from you. I'm up near Livingston. So we're looking at the same climate more or less.

 

[Zwy]

I will say that I don't blame Ian, he has been supportive through the process. Mpp Solar has been difficult for the most part. However, when I ordered 2 main boards for them, they got it to me in a couple of days direct from Taiwan. Perhaps the neutral bonding between the breaker panels or the ground-neutral bonds in the inverters themselves. I am not certain what the original issue was that started this chain of events but I am moving forward with a different inverter setup.

it’s not missing, I just have 3 strings of 4. Nothing parallel. That is why there is only one input to SP1. I am near Houston, Texas.

The reason I asked is I didn't see the extra string in this photo. https://diysolarforum.com/threads/lv-6548s-split-phase-not-awesome.54708/

As Gavin has stated, if you do have another problem downstream of the inverters, the next inverter brand could suffer the same fate. If I was attempting to troubleshoot this, I would correct the parallel path N-G bonding issue and I would disconnect AC in. I might even disconnect AC out to the subpanel, run only one inverter with the AC out to an outlet and see if it works. Then repeat the same with the other inverter with the first one off. This shows each inverter can operate as a single 120V unit. Then I would pair them with the neutrals tied together and check if I have 240V between the two inverters and can run loads off each 120V leg. Neutral will be floating if you do not have the screws installed, so this is only for testing purposes.

Only then would I tie in to the main and depending on if you choose common neutral, you tie in for N-G bond using the common neutral. Operate the unit again. Then I would tie into the subpanel with all breakers off. Then switch on each breaker until all are on.

It's possible you have a ground fault downstream, anything that would overload the inverter but if there is a ground fault, it should trip a breaker if properly sized or the inverter should shut down with a code.

One more thing, I did study the photo and did not see the current sharing cable which is the way it should be. If you did install it after the photo, then that would be a cause of the problem. I'm just double checking for possible causes. These are a pretty solid inverter, I own a pair but installed the EG4 6500EX so I could increase my string VOC for PV I mounted farther away.

 

[Zapper77]

I installed two LV6548's in Split phase hooked up to a subpanel for all of the necessities. I have had to replace the main boards several times. There must be something else wrong. I think I should have stuck with EG4 6500's, it may flicker but at least it appears to be more stable. At lease support is local in this country. Ian is great but he has to get permission from MPP solar in Taiwan. The system has been down for 5 days with no resolution. I am losing the faith in these units.
View attachment 133353

Can we see a photo of the AC wiring in side each inverter, the box under the left inverter and the electric panel on the left?

 

[DENWA]

Here is a better depiction of my current setup.
View attachment 137848

Cam I ask what you used to draw this?

 

[RGH69]

As Gavin has stated, if you do have another problem downstream of the inverters, the next inverter brand could suffer the same fate. If I was attempting to troubleshoot this, I would correct the parallel path N-G bonding issue and I would disconnect AC in. I might even disconnect AC out to the subpanel, run only one inverter with the AC out to an outlet and see if it works. Then repeat the same with the other inverter with the first one off. This shows each inverter can operate as a single 120V unit. Then I would pair them with the neutrals tied together and check if I have 240V between the two inverters and can run loads off each 120V leg. Neutral will be floating if you do not have the screws installed, so this is only for testing purposes.

Agreed, I will do this when the new inverters arrive.

Can we see a photo of the AC wiring in side each inverter, the box under the left inverter and the electric panel on the left?

One more thing, I did study the photo and did not see the current sharing cable which is the way it should be. If you did install it after the photo, then that would be a cause of the problem. I'm just double checking for possible causes. These are a pretty solid inverter, I own a pair but installed the EG4 6500EX so I could increase my string VOC for PV I mounted farther away.

I am going to change that setup because that box has all of the 4 gauge AC in and out wiring including Polaris connecters in it which makes it very hard to see. I am going to replace it with a wiring trough under both units and use conduit to all of the connections through the wiring trough. Then I can group and label everything so y'all can see it and tell me if anything is incorrect. I originally wanted to do this with the LV6548's but I would have to replace the MC-4 connectors. With the EG46500 I can do everything in conduit for a clean and organized setup.

Cam I ask what you used to draw this?

Microsoft Paint

 

[EastTexCowboy]

@RGH69 - Hopefully you can resolve this without any further damage, but you may want to consider using some flavor of monitoring software such as Solar Assistant. At least then you could dig a little deeper into what's going on and worst case scenario you could maybe see what was happening just prior to a failure if it does happen again. Just a thought.

 

[RGH69]

@RGH69 - Hopefully you can resolve this without any further damage, but you may want to consider using some flavor of monitoring software such as Solar Assistant. At least then you could dig a little deeper into what's going on and worst case scenario you could maybe see what was happening just prior to a failure if it does happen again. Just a thought.

Yep, I purchased one from Ian. I look forward to using it when the 6500's come in.

 

[Biigtiitan]

@RGH69 - Hopefully you can resolve this without any further damage, but you may want to consider using some flavor of monitoring software such as Solar Assistant. At least then you could dig a little deeper into what's going on and worst case scenario you could maybe see what was happening just prior to a failure if it does happen again. Just a thought.

Thank you for all your input, lots of great info. Solar Assistant is well worth it !!