LV6048 output neutral-ground bonding?

[FilterGuy]

I do not care for the current wiring where the L is fed back into the main panel and the N is in the main panel for the generator powered circuits either. Treat each part seperate as a subpanel,

Clearly, if the system is going into new construction, that is not the way it would be done. However, that is the way many retrofits get done when "common neutral" inverters like SolArk or Schnider are used. I am not as versed in retrofits with generators, but I would not be surprised if it is common there too.

I'm certain the way it is currently wired is not allowed under NEC.

I could not find anything in the NEC that would prevent it.... but the NEC is complex and hard to read. Do you happen to know what provision would prevent it?

 

[Zwy]

Clearly, if the system is going into new construction, that is not the way it would be done. However, that is the way many retrofits get done when "common neutral" inverters like SolArk or Schnider are used. I am not as versed in retrofits with generators, but I would not be surprised if it is common there too.

For several reasons, including serviceability, installation of a manual transfer switch between entrance panel and inverter would be advantageous.

I could not find anything in the NEC that would prevent it.... but the NEC is complex and hard to read. Do you happen to know what provision would prevent it?

Section 210-4(a) also states that all multiwire branch-circuit conductors must originate from the same panelboard.

Now if the subpanel is labeled as 240V only and fed only 240V circuits, then no neutral would be required. However, as this is feeding 120V circuits, there is a need for balance and a neutral is required. That is where 210-4(a) applies.

 

[eabyrd]

For several reasons, including serviceability, installation of a manual transfer switch between entrance panel and inverter would be advantageous.


Section 210-4(a) also states that all multiwire branch-circuit conductors must originate from the same panelboard.

Now if the subpanel is labeled as 240V only and fed only 240V circuits, then no neutral would be required. However, as this is feeding 120V circuits, there is a need for balance and a neutral is required. That is where 210-4(a) applies.

I'll start by saying I agree with you that there should be a transfer switch between the main panel and the sub-panel (unless those are break before make 3-way beakers or something equally exotic, that's not coming through in the diagram), and also that you must pull the neutrals over to work with an inverter like the MPP which creates its own bond. Howver, A "multiwire" branch circuit is a "branch circuit with a shared neutral. This means there are two or more ungrounded (hot) phase or system conductors with a voltage between them and a shared neutral."

These are to be avoided as a matter of course, but do exist in older construction, or anywhere the electrician was too cheap to do it right. If you have them, then absolutely both legs of that circuit must originate from the same panel, but 210-4(a) does not apply to normal 120 volt branches with only a single hot phase running in the branch.

If you look in the SolArk documentation they actually show how to implement a Protran MTS in the inverter's output stream to prevent the need for moving any circuits out of the main. This is an advantage of the shared neutral design.

 

[MrM1]

@FilterGuy
This diagram from the Midnite Solar SW e-Panel installation guide (for the Schneider SW) shows the incoming neutral from the main panel being bonded with the out going neutral output of the SW in the ePanel on both the input and output side of the SW.

Reading your earlier post and jpg, the SW always has the neutral pass through from input to output.

My question. In this diagram from the MN ePanel install for the SW

1. My assumption is in the panel marked "utility panel or generator" that this is the only place that there would be / should be a neutral and ground bond in this whole system

2. What happens in a grid down situation where the utility grid panel is no longer supplying AC pass through power to the SW at the grid AC input of the SW, what does that do to the neutral coming in from the grid panel? Is the SW now the supplier of the neutral to the whole system? Both the grid panel and the critical loads sub panel?

 

[FilterGuy]

This diagram from the Midnite Solar SW e-Panel installation guide (for the Schneider SW) shows the incoming neutral from the main panel being bonded with the out going neutral output of the SW in the ePanel on both the input and output side of the SW.

Interesting. There are other diagrams from Schneider that only show one side hooked to neutral. Since the Schnider has a hard connection between the input and output neutral, the two connections are redundant and create a loop. Personally, I would prefer to only hook one of the two up to avoid a loop that could create RFI problems.

1. My assumption is in the panel marked "utility panel or generator" that this is the only place that there would be / should be a neutral and ground bond in this whole system

That is correct. The schnider never switches disconnects the input neutral from the output neutral. Consequently, the output always 'sees' the N-G bond that should be in the utility panel.

What happens in a grid down situation where the utility grid panel is no longer supplying AC pass through power to the SW at the grid AC input of the SW, what does that do to the neutral coming in from the grid panel? Is the SW now the supplier of the neutral to the whole system? Both the grid panel and the critical loads sub panel?

The purpose of the N-G bond is to provide a low impedance path from neutral and ground so that in the event of a short between hot and ground there will be a high current to clear a fault between Hot and ground.



Let's look at a fault in the Schnider system above


The purple dashed line shows the fault path for the current needed to pop the breaker due to the fault.

 

[MrM1]

Interesting. There are other diagrams from Schneider that only show one side hooked to neutral. Since the Schnider has a hard connection between the input and output neutral, the two connections are redundant and create a loop. Personally, I would prefer to only hook one of the two up to avoid a loop that could create RFI problems.



That is correct. The schnider never switches disconnects the input neutral from the output neutral. Consequently, the output always 'sees' the N-G bond that should be in the utility panel.


The purpose of the N-G bond is to provide a low impedance path from neutral and ground so that in the event of a short between hot and ground there will be a high current to clear a fault between Hot and ground.

View attachment 80225

Let's look at a fault in the Schnider system above
View attachment 80234

The purple dashed line shows the fault path for the current needed to pop the breaker due to the fault.

Thanks so much for your kind and thoughtful response.

That has always been my question and thought. Why would Midnite Solar draw the connection of a neural from the utility panel to the inverter in, and then connect that neutral at the MN ePanel Busbar to the neutral out from the inverter? Maybe @SpongeboB Sinewave knows why MN showed it that way.

To my 2nd part, maybe I'm saying it wrong asking if in a grid down situation does the inverter "supply" the neutral. Perhaps as long as the neutral and ground are bonded back in the main panel, it does not matter where the hot power comes from, utility panel via the grid or the inverter. In either source for hot, the neutral will do its job.

 

[FilterGuy]

To my 2nd part, maybe I'm saying it wrong asking if in a grid down situation does the inverter "supply" the neutral.

Yes. It does

 

[philatio]

OK, now I am concerned with my purchase of the LV6048.

I passed on the Growatt with auto transformer due to it's issues.

My LV6048 arrives tomorrow. My EG4-LL batteries arrived today.

Here is my intended connection. Will this work safely
My main intent is as emergency backup, however I do have a couple circuits on the transfer switch I would like to run full time from the batteries. The side benefit being that I can cycle the batteries to keep them healthy.

An electrician wired in a reliance 310C manual transfer switch a month ago.

I planned on wiring the female half of an L14-30 generator cord directly to the L1, L2, G, and N of the LV6048 AC output which would then be plugged into the transfer switch inlet box.

I was going to take the other half of the cord and wire it directly to the L1, L2, G, and N of the LV6048 AC intput to charge the batteries. At the time there will be no PV connected.

And of course, the paralleled EG4 batteries would be wired to the LV6048. I have a 300A T Class fuse for the positive side of the batteries as well.

Am I asking for trouble here?

Any feed back would be greatly appreciated.

 

[FilterGuy]

OK, now I am concerned with my purchase of the LV6048.

I passed on the Growatt with auto transformer due to it's issues.

My LV6048 arrives tomorrow. My EG4-LL batteries arrived today.

Here is my intended connection. Will this work safely
My main intent is as emergency backup, however I do have a couple circuits on the transfer switch I would like to run full time from the batteries. The side benefit being that I can cycle the batteries to keep them healthy.

An electrician wired in a reliance 310C manual transfer switch a month ago.

I planned on wiring the female half of an L14-30 generator cord directly to the L1, L2, G, and N of the LV6048 AC output which would then be plugged into the transfer switch inlet box.

I was going to take the other half of the cord and wire it directly to the L1, L2, G, and N of the LV6048 AC intput to charge the batteries. At the time there will be no PV connected.

And of course, the paralleled EG4 batteries would be wired to the LV6048. I have a 300A T Class fuse for the positive side of the batteries as well.

Am I asking for trouble here?

Any feed back would be greatly appreciated.

I do not have direct experience with the LV6048 but there is no reason why it could not safely provide split phase.

Warning: This thread has mixed in discussions and drawings of a Schnider inverter..... be careful not to use those drawings as reference. The Schnieder has a fundamentally different approach to the grounding/bonding/neutral stuff.

 

[Zwy]

OK, now I am concerned with my purchase of the LV6048.

What is your concern?

I passed on the Growatt with auto transformer due to it's issues.

Smart move, be thankful you didn't get into that mess.

My LV6048 arrives tomorrow. My EG4-LL batteries arrived today.

Here is my intended connection. Will this work safely
My main intent is as emergency backup, however I do have a couple circuits on the transfer switch I would like to run full time from the batteries. The side benefit being that I can cycle the batteries to keep them healthy.

An electrician wired in a reliance 310C manual transfer switch a month ago.

I planned on wiring the female half of an L14-30 generator cord directly to the L1, L2, G, and N of the LV6048 AC output which would then be plugged into the transfer switch inlet box.

I was going to take the other half of the cord and wire it directly to the L1, L2, G, and N of the LV6048 AC intput to charge the batteries. At the time there will be no PV connected.

Is there a generator in here somewhere or are you wiring the AC input of the LV6048 to grid? From what I gather it is grid.

And of course, the paralleled EG4 batteries would be wired to the LV6048. I have a 300A T Class fuse for the positive side of the batteries as well.

Am I asking for trouble here?

Any feed back would be greatly appreciated.

 

[Zwy]

From Post # 11 of this thread, I conclude the LV6064 is not designed to have a connection between the input neutral and output neutral.

Therefore, the following changes need to be made to the 'inverter' diagram.

1) The neutral between the inverter panel and the main panel should be removed.

The LV6048 has an internal transformer and either switches neutral or isolates it from everything I've seen. It most likely is an isolation transformer as the unit is split phase.

2) The neutrals for all the loads connected to the inverter panel should be disconnected from the main panel and reconnected to the inverter panel.

Yes. As the unit has an internal transformer, the neutrals most definitely need to be moved.

3) Unrelated to post 11: The grounds of the inverter are all tied together internally, therefore there is a ground loop that should be broken by either 1) removing the ground wire from the inverter output to the inverter panel or 2) removing the ground connection between the main panel and inverter panel. (I would prefer #1)

Not following your reason for thinking a ground loop exists. In Bypass Mode the unit does not bond N-G according to post 11, when in inverter mode N-G are bonded.

I see no reason for a ground loop.

View attachment 80008

Also, Do NOT disable the dynamic bonding by removing the screw mentioned in post 11.

When the inverter is in pass-through mode (Powered by the main panel) the loads will 'see' the N-G bond in the main panel.
When the inverter is powered by the battery, it will internally create an N-G bond that the loads will 'see'.

This is correct.

 

[BuffaloTrace]

Here is my intended connection. Will this work safely
My main intent is as emergency backup, however I do have a couple circuits on the transfer switch I would like to run full time from the batteries. The side benefit being that I can cycle the batteries to keep them healthy.

An electrician wired in a reliance 310C manual transfer switch a month ago.

I planned on wiring the female half of an L14-30 generator cord directly to the L1, L2, G, and N of the LV6048 AC output which would then be plugged into the transfer switch inlet box.

I was going to take the other half of the cord and wire it directly to the L1, L2, G, and N of the LV6048 AC intput to charge the batteries. At the time there will be no PV connected.

And of course, the paralleled EG4 batteries would be wired to the LV6048. I have a 300A T Class fuse for the positive side of the batteries as well.

Am I asking for trouble here?

Any feed back would be greatly appreciated.

With the LV6048, can the generator plug safely supply the main panel this way even if the main panel is neutral/ground bonded? I too am wondering this as many just have emergency/grid down scenario useage in mind.

 

[FilterGuy]

Not following your reason for thinking a ground loop exists. In Bypass Mode the unit does not bond N-G according to post 11, when in inverter mode N-G are bonded.

I see no reason for a ground loop.

The AC-IN-Ground and AC-out-Ground of the inverter are tied together. This creates a loop as shown below

 

[FilterGuy]

With the LV6048, can the generator plug safely supply the main panel this way even if the main panel is neutral/ground bonded? I too am wondering this as many just have emergency/grid down scenario useage in mind.

1) If the generator also has a N-G ground (Most don't), then there must be a transfer switch before the critical loads panel that switches both hot and neutral... or the N-T ground must be removed from the generator.... and then it becomes #2 below.

2) If the generator does NOT have an N-G ground (typical), then there must be either a transfer switch before the critical loads panel that switches the Hot line or a generator lock-out between the main breaker and generator breakers in the panel.

 

[BuffaloTrace]

1) If the generator also has a N-G ground (Most don't), then there must be a transfer switch before the critical loads panel that switches both hot and neutral... or the N-T ground must be removed from the generator.... and then it becomes #2 below.

2) If the generator does NOT have an N-G ground (typical), then there must be either a transfer switch before the critical loads panel that switches the Hot line or a generator lock-out between the main breaker and generator breakers in the panel.

I quoted philatio as his plan is to wire in the female (twist lock type?) generator cord directly to the AC out. Can The generator Male inlet be wired into the mains even if the main panel is neutral/ground bonded. I believe the intent would be for grid down emergency power. Otherwise his inverter is going to power other loads full time.

 

[FilterGuy]

I quoted philatio as his plan is to wire in the female (twist lock type?) generator cord directly to the AC out. Can The generator Male inlet be wired into the mains even if the main panel is neutral/ground bonded. I believe the intent would be for grid down emergency power. Otherwise his inverter is going to power other loads full time.

OK... I may not have answered your question. Sorry.

I went back and read what @philatio said but I am not sure I am following his plan. I would need a diagram.

 

[BuffaloTrace]

No worries. Was wondering myself, as I read through the thread and came across his safety concern on wiring the mpp in such a way...I had not considered doing something split phase with an mpp inverter with anything but a sub panel.
But I assumed for emergency useage in grid down scenario that philatio was considering feeding the main panel through a standard household generator rated inlet plug.
If inverter mode usung the l1, l2, n, and g, is neutral-ground bonded within the inverter, than the generator inlet would be going to neutral ground bonded main panel....

 

[philatio]

Here is a visual of my intent. I was going to go with the LVX6048, but opted for the LV6048 instead. So ignore the image of the LVX.

Note, for now no PV. Charging will be done via AC as shown, and generator if it's needed.

 

[FilterGuy]

Here is a visual of my intent. I was going to go with the LVX6048, but opted for the LV6048 instead. So ignore the image of the LVX.

Note, for now no PV. Charging will be done via AC as shown, and generator if it's needed.

That type of transfer switch is nice in a retro-fit but it does not switch neutral. It counts on the same neutral line to the load for both input sources. What that ends up meaning is that the neutral on the inverter input ends up being the same as the neutral on the inverter output. I don't know if the LVX can handle this....particularly since it is a low-frequency inverter that probably has a center tap isolation transformer on the output. It is possible the LVX could handle this, but, the MPP documentation is not detailed enough to say. Personally, I would want MPP support to approve this before I set it up.

BTW: I do not know if that type of transfer switch can be set up for 240V.....but I could be wrong about that.

 

[philatio]

I am not using the LVX6048. I was going to but purchased the LV6048 instead.

The transfer switch can do 240 according the the manufacturer:

MODEL​	310CRK​
MODEL DESCRIPTION​	Pro/Tran 2​
MAX. GENERATOR RUNNING WATTS​	7500​
PHASE​	Single​
MAX. SINGLE-POLE CIRCUITS​	10​
MAX. DOUBLE-POLE CIRCUITS​	5​
MAX. RATING PER CIRCUIT​	2/30A, 8/20A​
MAX. COMBINED LOAD @ 125 VAC​	60​
MAX. COMBINED LOAD @ 250 VAC​	30​
POWER INLET, NEMA​	L14-30​
CORD SIZE [gauge]​	10​
RECCOMMENDED CORD SIZE [gauge]​	10​
CONDUIT SIZE [inches]​	1​
CONDUIT LENGTH [inches]​	18​
WATTMETERS​	Yes​
SHIPPING WEIGHT [lbs.]​	25​
DIMENSIONS H x W x D [inches]​	11 x 11.75 x 4.5​
CABINET TYPE, NEMA​	Indoor, NEMA​
CORD LENGTH [feet]​	10​

The transfer switch has 1 double pole 30A breaker for the heat pump which is a 25A breaker in the main panel, (not for resistive heat coils) .
The rest are 20A breakers.

I believe I'm ok hooking up the AC out directly to the transfer switch, at least according to one of Will's videos:

in this video he talks about the LV5048 which was replaced by the LV6048.

Is the issue with charging that batteries from the AC output?