Growatt 3000 SPF Floating Neutral (Solved for Now)

FilterGuy

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At the bottom of the sticker, is there another sticker/barcode or QR code with the model? It might say "P/N" instead of "model number". The model number should look something like this: P/N: SKSL00.xxxxxxx.

I do not know how their sequencing works but my *GUESS* is that anything with P/N: SKSL00.001xxxx is the new hardware and P/N: SKSL00.000xxxx is the old hardware.

1637892619873.png
1637894446148.png
 
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ddanley

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At the bottom of the sticker, is there another sticker/barcode or QR code with the model? It might say "P/N" instead of "model number". The model number should look something like this: P/N: SKSL00.xxxxxxx.

I do not know how their sequencing works but my *GUESS* is that anything with P/N: SKSL00.001xxxx is the new hardware and P/N: SKSL00.000xxxx is the old hardware.

View attachment 73548
View attachment 73550

Here is my sticker... I was looking for anything SKSL00.00X... Mine is pretty different for some reason.
 

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ddanley

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I used 3 different QR code reader apps, and all come back with no matches. Not very impressive. :rolleyes:

I can only speculate it is the newer model since I don't have option 24...

A follow up question if you don't mind... If I implemented what Chris did, Would I connect an additional wire (Gauge size?) directly from the AC Input Neutral inside the cable compartment of the Growatt to the Neutral of my GFCI outlet?
 

FilterGuy

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I used 3 different QR code reader apps, and all come back with no matches. Not very impressive. :rolleyes:
The model number on the sticker seems strange. I sent the pic to Growatt asking if it looks right to them. I'll post here if I hear back from them.

I can only speculate it is the newer model since I don't have option 24...
It appears that they changed the firmware on some models with the older hardware, so the presence or absence of Program 24 is not a good indication of HW rev.
A follow up question if you don't mind... If I implemented what Chris did, Would I connect an additional wire (Gauge size?) directly from the AC Input Neutral inside the cable compartment of the Growatt to the Neutral of my GFCI outlet?
The connection can be inside the cable compartment or it can be outside. However, the gauge wire needs to be able to handle the full current
and for a 3000W inverter that is 3000W/120V=25A.... That calls for a 10AWG wire. It is probably going to be difficult to get both the 10AWG 'main wire' and the 10AWG 'jumper' into the connector on the Growatt so I would lean toward making the connection someplace outside the cable compartment.
 

FilterGuy

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I can only speculate it is the newer model since I don't have option 24...
The best way to figure it out is to see if the output is floating when the inverter is running off the battery..... Check to see if there is voltage between the Neutral and Ground wire.
 

FilterGuy

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If I implemented what Chris did,
If you do have the newer model, then implementing the 'Chris' solution would result in dual N-G bonds when the unit is running off the battery. That is not a good thing. (You can detect a dual N-G bond by checking for current on the ground wire between the inverter and the grid connection while there is a load on the output of the inverter)
 

Librelec

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The alternative to bonding the incoming, and outgoing Neutrals, is having the loads on the same neutral bar as the incoming supply.

This is a fairly standard procedure for on-grid hybrid inverters that offer battery-only backup (here in Australia, anyway).

Any thoughts on the above?
 

FilterGuy

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The alternative to bonding the incoming, and outgoing Neutrals, is having the loads on the same neutral bar as the incoming supply.

This is a fairly standard procedure for on-grid hybrid inverters that offer battery-only backup (here in Australia, anyway).

Any thoughts on the above?
Do you mean like this:
1641942561840.png

It seems to me that this would only work if the inverter has a common neutral. I know that some inverters (Like Schnider and Solark) have common neutral and I am pretty sure the Growatts do not.

BTW: IMHO, inverters should all either dynamically generate the NG-Bond as appropriate or have a common Neutral... but alas, that is not the case.
 

Librelec

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Do you mean like this:
View attachment 79263

It seems to me that this would only work if the inverter has a common neutral. I know that some inverters (Like Schnider and Solark) have common neutral and I am pretty sure the Growatts do not.

BTW: IMHO, inverters should all either dynamically generate the NG-Bond as appropriate or have a common Neutral... but alas, that is not the case.
Essentially, yes (Although the output neutral should continue and connect to the Critical Loads Box Neutral bar)

Isn't what you've drawn giving the inverter that common Neutral?

I completely agree with your call that a dynamically created NG bond is better (and it's what I do in manual transfer switch jobs that I install) but this inverter doesn't have that capability, and bringing in a whole heap of extra relays and contacts (or, points of failure) doesn't seem worth it, when you can just bond the neutrals and use the one NG bond at the main switchboard.

Yer?

Also, in Australia, you can't use contactors to create that NG bond, and be compliant with code (in on-grid installs). Rightfulyl so, because of the multiple points of failure for something so critical to the safety of the installation. So again, this is a better way to handle that.


In my attached pic (remember I'm from Australia) Red (and Blue) is Active, Black is Neutral.

edit: To comment on your "common Neutral" part. If we were to do this, wouldn't it create a parallel path between the neutrals? Which could overload one of them, in certain run conditions?

I feel like you only want to do this, if the neutrals are NOT bonded at the inverter.
 

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FilterGuy

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(Although the output neutral should continue and connect to the Critical Loads Box Neutral bar)
OK... I understand what you mean now. Yes, that is the same as jumpering the input and output neutrals on the inverter.
1641954458255.png
In my attached pic (remember I'm from Australia) Red (and Blue) is Active, Black is Neutral.
Yes. The way you have it drawn is what I am calling 'common neutral': The input and output neutral are tied together inside the inverter. (Maybe I should figure out a better term for it. )

Like I said before, some inverters have a hard connection between the input and output neutrals (SolArk and Schnider for example). Unfortunately, not all inverters do this. In particular, the older Growatts do not have a hardwired connection between the input and output neutral. (I do not know what the newer models do) Fortunately, Growatt support said it is acceptable to jumper the input and output neutrals together externally on the older models. This effectively creates what I am calling a 'common neutral'.

However, I would not assume all inverters can have the input and output neutral tied together externally. I would want confirmation from the manufacturer before I did it.

edit: To comment on your "common Neutral" part. If we were to do this, wouldn't it create a parallel path between the neutrals? Which could overload one of them, in certain run conditions?
Correct, if the inverter already has the input and output neutral tied together, you would not want to do it externally. I am not sure there is any safety issue with adding an external connection, but it would create a loop that could have RFI noise implications.
 

FilterGuy

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Also, in Australia, you can't use contactors to create that NG bond, and be compliant with code (in on-grid installs).
Interesting. If the inverter does not have the Input and output neutral tied together.... how do you deal with maintaining the N-G Bond when the inverter goes into invert mode and disconnects the output neutral from the input neutral? If the inverter allows an external connection between the input and output neutral (Like Growatt does), then I see how to do it. If the inverter does not allow tieing the neutrals together, I don't see how to maintain an N-G bond without a relay or contactor of some kind.
 

Librelec

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Interesting. If the inverter does not have the Input and output neutral tied together.... how do you deal with maintaining the N-G Bond when the inverter goes into invert mode and disconnects the output neutral from the input neutral? If the inverter allows an external connection between the input and output neutral (Like Growatt does), then I see how to do it. If the inverter does not allow tieing the neutrals together, I don't see how to maintain an N-G bond without a relay or contactor of some kind.
The standard installation procedure for on-grid hybrid inverters is what I've drawn above. Put the output loads on the same neutral busbar as the grid. That means, you have 2 "supplies" in the one switchboard. You can have "non-essential" loads (fed by the grid) AND "essential" loads fed by the inverter/battery, on the same Neutral bar. The non-essential loads don't work when in battery mode.

By doing the above, the installation always maintains the NG bond found in the main switch board. Follow the paths of my Ground and Neutral (black) cables in "DB1 Essential" in my above diagram. This way you don't need to create a new NG bond when in battery mode, because you always have a connection to the NG bond (MEN point) in the main switch board.

Appropriate labelling is an important part of our compliance.
 
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FilterGuy

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The standard installation procedure for on-grid hybrid inverters is what I've drawn above. Put the output loads on the same neutral busbar as the grid. That means, you have 2 "supplies" in the one switchboard. You can have "non-essential" loads (fed by the grid) AND "essential" loads fed by the inverter/battery, on the same Neutral bar. The non-essential loads don't work when in battery mode.

By doing the above, the installation always maintains the NG bond found in the main switch board. Follow the paths of my Ground and Neutral (black) cables in "DB1 Essential" in my above diagram. This way you don't need to create a new NG bond when in battery mode, because you always have a connection to the NG bond (MEN point) in the main switch board.

Appropriate labelling is an important part of our compliance.
Interesting.... Does MPP sell in Australia and have you ever hooked them up that way?
 

Librelec

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Interesting. If the inverter does not have the Input and output neutral tied together.... how do you deal with maintaining the N-G Bond when the inverter goes into invert mode and disconnects the output neutral from the input neutral? If the inverter allows an external connection between the input and output neutral (Like Growatt does), then I see how to do it. If the inverter does not allow tieing the neutrals together, I don't see how to maintain an N-G bond without a relay or contactor of some kind.
I just wanted to update this thread for the sake of clarity, and anyone else reading along.

After actually going to site and testing the inverters it turns out the Output Neutral is bonded to the Ground when in normal operation. It may be a difference in firmware, so when using these inverters, I must stress the importance of testing after installation.

So the single line diagram for the AC cabling of my installation is now attached.

I wasn't able to verify whether the bond remains when in AC bypass yet, and that's the final test I will need to do. The inverter was difficult to get in to AC bypass mode (disconnecting the batteries set the inverter in to fault mode, instead of bypass mode) so I have to wait on site for when the batteries run low (with low/no PV) and test.
 

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FilterGuy

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I wasn't able to verify whether the bond remains when in AC bypass yet, and that's the final test I will need to do. The inverter was difficult to get in to AC bypass mode (disconnecting the batteries set the inverter in to fault mode, instead of bypass mode) so I have to wait on site for when the batteries run low (with low/no PV) and test.
Most modern inverters have a setting that allows you to tell it to always use the grid when it is available.

On the Growatt SPF 3000TL LVM, it is program #1:

1642719336385.png

Set program 1 to Utl and it should switch to the AC-In any time the AC-in is available.
 

Librelec

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Yep, we found that setting, and it didn't work.

Even after power cycling the inverter. Not sure what the issue was.
 

Librelec

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Most modern inverters have a setting that allows you to tell it to always use the grid when it is available.

On the Growatt SPF 3000TL LVM, it is program #1:

View attachment 80568

Set program 1 to Utl and it should switch to the AC-In any time the AC-in is available.
Not sure what I was doing wrong previously, but it worked fine the second time around. Getting it in to AC bypass mode allowed me to test if there was any current on the incoming Ground cable.

With around 7A on the incoming Neutral cable, there was 0.01A on the Ground cable.

So, with the firmware version that I have, the Growatt SPF5000ES appropriately creates the N/G bond in battery mode, and removes the N/G bond in AC bypass mode.

(I imagine this is why I've seen some people mention a firmware update broke the "external N/G bond relay" functionality - it's done internally now)

I've linked a copy of my finalised AC wiring for the installation.

I must stress, by the sounds of what others have posted, this functionality is dependant on what firmware version you have. So updating the firmware seems a fairly important step for this inverter.

SLD2.jpg
 
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