FINAL ANSWER on AC out grounding on Growatt SPF3000TL LVM-24P

gelmjw · Feb 24, 2022

It depends.

Here is what I know about my model SKSL00 0010700.
I learned this while trying to power an AC device that requires a ground.
The Growatt's AC out is NEVER grounded. Not with grid, generator or inverter(battery).

I ask that any comments please include the model # related to the comment. I wasted several days reading conflicting info here and came to learn that Growatt has made changes and offered modification advice to other models and it is very confusing to anyone trying to extract useful info.

FilterGuy · Feb 24, 2022

gelmjw said:
Here is what I know about my model SKSL00 0010700.

Oh Wow! Growatt told me that the models that have the internal bonding relay are:
•SPF 3000 TL LVM-24P – model# SKSL00.0010200
•SPF 3000 TL LVM-48P – model# SKSL00.0010000

Your model number seems to be *after* the model number with the change.... so if both bits of info are correct, then numbers are not sequential.
(I would have guessed that SKSL00 0010700 came *after* SKSL00.0010200 and therefore would have the bonding relay.

What a frigg'n mess!!!

BTW: This is what I wrote up for inverters before the change:

gelmjw · Feb 25, 2022

FilterGuy said:
Oh Wow! Growatt told me that the models that have the internal bonding relay are:
•SPF 3000 TL LVM-24P – model# SKSL00.0010200
•SPF 3000 TL LVM-48P – model# SKSL00.0010000

Your model number seems to be *after* the model number with the change.... so if both bits of info are correct, then numbers are not sequential.
(I would have guessed that SKSL00 0010700 came *after* SKSL00.0010200 and therefore would have the bonding relay.

What a frigg'n mess!!!

BTW: This is what I wrote up for inverters before the change:

View attachment 85191

This info may help with aging the model numbers.

I got my Growatt in May 2021 after waiting two months.

Yes, I saw yours and others posts and that is when I learned I may have a newer Growatt that what was being discussed.

I don't have 'program 24' on the LCD Display, or an external relay port. I have not opened the cover to see about a bonding screw.

Quattrohead · Feb 25, 2022

I would have thought the metal case would be grounded no matter where in the world. Even if the L/N or L1/L2 are totally floating you should have a ground in/out connected to the case.

acdoctor · Feb 25, 2022

For clarification are we discussing neutral ground bond? Or case/earth ground? Or both?

FilterGuy · Feb 25, 2022

Quattrohead said:
I would have thought the metal case would be grounded no matter where in the world. Even if the L/N or L1/L2 are totally floating you should have a ground in/out connected to the case.

acdoctor said:
For clarification are we discussing neutral ground bond? Or case/earth ground? Or both?

We are talking about the Neutral-Ground bonding (or lack of it on some units).

All inverters I have ever seen connect the Input Ground, Output Ground, and metal case together.

gelmjw · Feb 25, 2022

I am only saying that the three light circuit tester showed only one yellow light indicating a 'no ground' fault.

I have no idea about the case. I don't know anything concerning this comment or whether or what is a good thing or a bad thing related to my Growatt. If it is important that I know this, please specify exactly how I can find out.

I have not seen a lot of things, but, what I do know is that in order to get my device to run I used a power strip to plug in a NGB plug into the AC out circuit to eliminate the fault.

I am done using the device right now and do not need the AC out to be grounded at this time.

acdoctor · Feb 25, 2022

I will investigate mine as soon as the ice melts off the trailer to where I can open the doors. The BMS temperature shows the mini split is keeping it warm. I don’t want to break anything getting in so I will wait.

gelmjw · Feb 25, 2022

acdoctor said:
I will investigate mine as soon as the ice melts off the trailer to where I can open the doors. The BMS temperature shows the mini split is keeping it warm. I don’t want to break anything getting in so I will wait.

The manual page you posted could have come from my manual, right down to the page number.

gelmjw · Feb 25, 2022

FilterGuy said:
We are talking about the Neutral-Ground bonding (or lack of it on some units).

All inverters I have ever seen connect the Input Ground, Output Ground, and metal case together.

Perhaps Growatt is the one that is finally doing grounding right after all.

That is exactly what my Yamaha inverter genny has done since 2013. Perhaps Yamaha has had it right all along as well.

I had to learn to use the NGB plug quite some time ago. I did use an inverter/charger with the Yamaha prior to the Growatt. In that case, I used the NGB on the genny with the thinking that I was fixing the genny's output that 'lacked' a ground like I got with grid AC. I don't recall ever trying the NGB on the AC out of that inverter. I wonder now if that would have been okay as well.

I am feeling very, perhaps unjustifiably, comfortable with the Yamaha and Growatt approach.

Edit-I corrected spelling of Yahama to Yamaha.

acdoctor · Feb 27, 2022

I don’t have the little plug tester but here I am using a cheep meter. First is grid connected and of course grid has NG bond. Last is inverting grid completely disconnected.

FilterGuy · Feb 27, 2022

acdoctor said:
I don’t have the little plug tester but here I am using a cheep meter. First is grid connected and of course grid has NG bond. Last is inverting grid completely disconnected.

It looks like you have one of the older models. This is the way GW says to deal with the bonding:

FilterGuy · Feb 27, 2022

The nice thing about the way Growatt says to handle the bonding is that is essentially creates a Common Neutral between input and output. That means that if you want to put a transfer switch before the load, you don't have to switch the neutral.

Aakelley · Mar 2, 2022

I have tested mine with the plug tester and it shows proper NG bond when on AC and open when on battery only. So I think I need to get one of those continuous duty relays. Any suggested part numbers / links?

BuffaloTrace · Mar 2, 2022

I would think its a safe assumption to believe there is never NG bond during AC pass through.
Let's get a master list going of inverters and serials with and without NG bond on inverter/battery mode.
For versatility factors we can add the manufacturer approved work arounds for each setup depending on where they end up on the list.

FilterGuy · Mar 2, 2022

Aakelley said:
I have tested mine with the plug tester and it shows proper NG bond when on AC and open when on battery only. So I think I need to get one of those continuous duty relays. Any suggested part numbers / links?

Do you have a stationary install or is it in an RV?

BuffaloTrace said:
Let's get a master list going of inverters and serials with and without NG bond on inverter/battery mode.

Grounding details for specific make/model of inverters

To get to the paper, click on the orange button at the top of the screen. It is important to understand how an inverter handles grounding in order to set it up correctly. Unfortunately, many inverters do not provide adequate documentation on...

diysolarforum.com

joshgray · May 2, 2022

FilterGuy said:
Do you have a stationary install or is it in an RV?

Grounding details for specific make/model of inverters

To get to the paper, click on the orange button at the top of the screen. It is important to understand how an inverter handles grounding in order to set it up correctly. Unfortunately, many inverters do not provide adequate documentation on...

diysolarforum.com

I really appreciate the details in the updated page #19, especially the detail of stationary versus mobile with regards to GFCI. Much kudos!

SYKSolar · Jun 14, 2022

FilterGuy said:
Oh Wow! Growatt told me that the models that have the internal bonding relay are:
•SPF 3000 TL LVM-24P – model# SKSL00.0010200
•SPF 3000 TL LVM-48P – model# SKSL00.0010000

Your model number seems to be *after* the model number with the change.... so if both bits of info are correct, then numbers are not sequential.
(I would have guessed that SKSL00 0010700 came *after* SKSL00.0010200 and therefore would have the bonding relay.

What a frigg'n mess!!!

BTW: This is what I wrote up for inverters before the change:

View attachment 85191

Good Morning FilterGuy, (Paul?),
SPF 3000 TL LVM-ES Model doesn't say it is 24V or 48V. I received mine 2 weeks ago. Need advice from you.

Continuity test showed AC Output N-G bonded; AC output G & AC input G bonded. Both AC Ns not bonded.

Signature Solar (SS) is nut on tech support as they told me it does dynamic bonding where as Growatt (GW) said no. Told SS GW said then one guy from SS said this:

There is a screw on the main board that Growatt is supposed to remove but we have found that has not been the case which is why we let customers know that bond is present. You can test the continuity on your inverter and if you are seeing any you can remove the top cover and there will be a grounding screw on the main board that will need to be removed and then you will need to have that ground neutral bond in your breaker panel.

I emailed them (SS) and asked where is the screw etc, should I remove it and still waiting for the answer. Do I jump the two Neutrals as described on your diagram? What is your recommendation. I haven't hook up my unit yet.
Thanks

FilterGuy · Jun 14, 2022

SYKSolar said:
Good Morning FilterGuy, (Paul?),
SPF 3000 TL LVM-ES Model doesn't say it is 24V or 48V. I received mine 2 weeks ago. Need advice from you.

The answers around the bonding and grounding are the same for both the 24 & 48V models.

SYKSolar said:
Signature Solar (SS) is nut on tech support as they told me it does dynamic bonding where as Growatt (GW) said no. Told SS GW said then one guy from SS said this:

There is a screw on the main board that Growatt is supposed to remove but we have found that has not been the case which is why we let customers know that bond is present. You can test the continuity on your inverter and if you are seeing any you can remove the top cover and there will be a grounding screw on the main board that will need to be removed and then you will need to have that ground neutral bond in your breaker panel.

I emailed them (SS) and asked where is the screw etc, should I remove it and still waiting for the answer

Yes.... Getting reliable info on Growatts is a frustrating exercise...... and they made it a lot worse when they changed how the bonding works without changing the model numbers.

The fact that you are measuring continuity on the output N & G tells me you have the version that does the internal dynamic bonding. (This would make sense given it is a new unit) I do not have direct experience with the newer models, but I am 99% sure that the bond is *not* enabled in pass-through mode and *is* enabled at all other times. (Off, inverter mode, standby, etc).

You don't say it explicitly, but your post kinda implies it is a single unit (You are not stacking 2 units to get a split-phase system).

So.... based on what I have gleaned from your message, you should not need to connect the input & output neutrals and you should not have to remove the internal bonding screw.

SYKSolar · Jun 14, 2022

FilterGuy said:
The answers around the bonding and grounding are the same for both the 24 & 48V models.

Yes.... Getting reliable info on Growatts is a frustrating exercise...... and they made it a lot worse when they changed how the bonding works without changing the model numbers.

The fact that you are measuring continuity on the output N & G tells me you have the version that does the internal dynamic bonding. (This would make sense given it is a new unit) I do not have direct experience with the newer models, but I am 99% sure that the bond is *not* enabled in pass-through mode and *is* enabled at all other times. (Off, inverter mode, standby, etc).

You don't say it explicitly, but your post kinda implies it is a single unit (You are not stacking 2 units to get a split-phase system).

So.... based on what I have gleaned from your message, you should not need to connect the input & output neutrals and you should not have to remove the internal bonding screw.

Thanks for your inputs and advice. Happy you figure out what I should not do.

I am not stacking. It is just 1 inverter and a 48V EG4 battery mainly to support my detached garage with washing machine, dryer, garage opener , a freezer, and a refrigerator. It is just a starter project and may expand with another inverter later.
I trust your judgement and analysis.

The following is what Growatt emailed me. The statement is ambiguous to me. Kind like "Yes and No" answer. Didn't he imply "doesn't do internal dynamic bonding" just in bypass mode?

FilterGuy · Jun 14, 2022

SYKSolar said:
Thanks for your inputs and advice. Happy you figure out what I should not do.

I am not stacking. It is just 1 inverter and a 48V EG4 battery mainly to support my detached garage with washing machine, dryer, garage opener , a freezer, and a refrigerator. It is just a starter project and may expand with another inverter later.
I trust your judgement and analysis.

The following is what Growatt emailed me. The statement is ambiguous to me. Kind like "Yes and No" answer. Didn't he imply "doesn't do internal dynamic bonding" just in bypass mode?
View attachment 98591

Wow!!! That statement from Growatt about their own product is obviously wrong. If there was no internal bonding you would never see continuity between neutral and ground.

Just to be sure: Once you have it set up check the voltage between neutral and ground both when on battery and in pass-through. (Do it without a load on the output of the inverter. You should see no voltage (or very low voltage) if it has a bond in both cases.

Assuming it has the bond in both cases, you can verify there is only one bond by checking for current on the Equipment Grounding Conductor between the Inverter and the main breaker panel (This time do it while there is a hefty load on the inverter). If there is no current on the ground, there is only one bond.

SYKSolar · Jun 14, 2022

FilterGuy said:
Wow!!! That statement from Growatt about their own product is obviously wrong. If there was no internal bonding you would never see continuity between neutral and ground.

Just to be sure: Once you have it set up check the voltage between neutral and ground both when on battery and in pass-through. (Do it without a load on the output of the inverter. You should see no voltage (or very low voltage) if it has a bond in both cases.

Assuming it has the bond in both cases, you can verify there is only one bond by checking for current on the Equipment Grounding Conductor between the Inverter and the main breaker panel (This time do it while there is a hefty load on the inverter). If there is no current on the ground, there is only one bond.

I trust and acknowledge your expertise!

I am confused which is right - whether the AC Output N-G should be bonded together or not . I thought the old model was said to be bond together and shouldn't.
My guess/understanding with the term "dynamic" bonding internally is: On AC output - Without N-G bond so that when the inverter is not in bypass mode, the inverter's program will bond them together. So my understanding was wrong?

In order to do the voltage check under different scenarios, under program 01- output source priority. The default is most likely solar when I turn on the system. Is there a way I can temporarily setup on Battery or Utility Grid so that I can check the voltages on N-G? Otherwise, I would have to do one or two of those steps at midnight .

FilterGuy · Jun 14, 2022

SYKSolar said:
I am confused which is right - whether the AC Output N-G should be bonded together or not . I thought the old model was said to be bond together and shouldn't.

The old version had no internal bonding but provided a dry contact that was supposed to be used to set up an external bonding relay for generating the bond when on battery power. This never worked very well (Primarily because they gave no instructions on how to do it and so people never did it).

The new version has the bonding relay built-in.

Your set-up will be something like this:

SYKSolar said:
My guess/understanding with the term "dynamic" bonding internally is: On AC output - Without N-G bond so that when the inverter is not in bypass mode, the inverter's program will bond them together. So my understanding was wrong?

No that is correct. When the inverter is on battery the output is disconnected from the main breaker panel so the internal bonding relay connects neutral and ground. When the inverter is in passthrough mode, the internal bonding really disconnects the bond and the system uses the bond in the main breaker box feeding the AC in.

SYKSolar · Jun 15, 2022

FilterGuy said:
The old version had no internal bonding but provided a dry contact that was supposed to be used to set up an external bonding relay for generating the bond when on battery power. This never worked very well (Primarily because they gave no instructions on how to do it and so people never did it).

The new version has the bonding relay built-in.

Your set-up will be something like this:

View attachment 98656

No that is correct. When the inverter is on battery the output is disconnected from the main breaker panel so the internal bonding relay connects neutral and ground. When the inverter is in passthrough mode, the internal bonding really disconnects the bond and the system uses the bond in the main breaker box feeding the AC in.

Thank you for the info. and taking the trouble to draw a sketch. That is exactly what my Load box look like.

I looked at Will P's video on the sequence of turning the system on. He turned on Battery first, follow by inverter and then the solar panel. I am using a 10 awg 20 amps extension cord readly to plug into a non- GFCI 20 Amps outlet as the AC input. I believe I need to keep the AC input to the inverter on at all times to have N-G tied to the Main Service panel when the system is in battery or solar mode. Correct?

Another way I think is to add a toggle switch on the Input 20A outlet to keep the N & G feed into the inverter even the Input outlet is toggled off. Correct?
Here are what my AC In & OUT look like.

FilterGuy · Jun 15, 2022

SYKSolar said:
I believe I need to keep the AC input to the inverter on at all times to have N-G tied to the Main Service panel when the system is in battery or solar mode. Correct?

Correct

SYKSolar said:
Another way I think is to add a toggle switch on the Input 20A outlet to keep the N & G feed into the inverter even the Input outlet is toggled off. Correct?

Sorry.... I don't understand what you are describing.

FINAL ANSWER on AC out grounding on Growatt SPF3000TL LVM-24P

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