Growatt SPF-5000-ES AT and N/G solutions

[timselectric]

First, let's point out the issues with this inverter for use in a split-phase system.

1) this inverter was designed for use in a 230v grounded installation. (European standards)
It's input and output are L1 and "N". This input "neutral" is expected to be grounded by the grid, and at the building service main panel. In bypass mode, this grounded "neutral" is passed through the inverter to the loads panel. In battery mode, the inputs are disconnected and the inverter will internally bond the output "neutral" with the inverter case and ground terminals. (This connects a hot wire to ground, in the US)

When using this inverter in a split-phase configuration. You need 240v single phase ungrounded. Then you use a transformer to create the midpoint tap for the neutral.
This gives you 120/240 split-phase.
This neutral should be grounded at all times, for life safety.

Signature Solar has worked with Growatt to modify the design so that the 2 lines are ungrounded through the inverter. (By removing the grounding system on the main board.) This stops the internal grounding relay from connecting "N" to ground.

2) the use of an AT (auto transformer) , creates the neutral in a very efficient way. And does so in a small package.
It's connected to the loads panel and needs to have its neutral bonded to the ground.
But, if you bond its neutral at the loads panel, you will create a ground loop between the loads panel and the main panel. This happens only when the inverter is in bypass mode. This is undesirable and very dangerous.

To avoid the N/G loop. Run a neutral from the main panel to the loads panel. This neutral is already bonded at the main panel, and provides short protection at the loads panel.
But, this puts the AT in parallel with the grids transformer.
This is undesirable, because the AT can try to carry the loads of the grids transformer.

To solve all of these issues, this is what I have done.

1) I ran a neutral conductor from the main panel to the loads panel. (Not bonded at the loads panel)
This provides a neutral for the loads in bypass mode. And provides the N/G bond from the main panel, in all modes.

2) install a relay on the AT feed conductors. Which is controlled by the inverter grounding relay. To only turn on the AT in battery mode.

To access the inverter grounding relay signal, I connected to the board at the screw location that was designed to ground the output "N" in battery mode.
This was done by a ring terminal and a non conductive nylon 3mm x 8mm machine screw.
And another ring terminal at the internal "L" terminal. This gives me a 240v signal.

Now, the AT is never connected to the loads at the same time as the grid. (No load sharing)

And, the loads panel neutral is always bonded. (From the main panel's N/G bonding point)

I also added another relay between the inverter grounding relay signal and the AT relay.
This keeps the internal inverter power isolated from external power. (This was for my own piece of mind)

 

[Trip.Diamond]

First, let's point out the issues with this inverter for use in a split-phase system.

1) this inverter was designed for use in a 230v grounded installation. (European standards)
It's input and output are L1 and "N". This input "neutral" is expected to be grounded by the grid, and at the building service main panel. In bypass mode, this grounded "neutral" is passed through the inverter to the loads panel. In battery mode, the inputs are disconnected and the inverter will internally bond the output "neutral" with the inverter case and ground terminals. (This connects a hot wire to ground, in the US)

When using this inverter in a split-phase configuration. You need 240v single phase ungrounded. Then you use a transformer to create the midpoint tap for the neutral.
This gives you 120/240 split-phase.
This neutral should be grounded at all times, for life safety.

Signature Solar has worked with Growatt to modify the design so that the 2 lines are ungrounded through the inverter. (By removing a single screw on the main board.) This stops the internal grounding relay from connecting "N" to ground.

2) the use of an AT (auto transformer) , creates the neutral in a very efficient way. And does so in a small package.
It's connected to the loads panel and needs to have its neutral bonded to the ground.
But, if you bond its neutral at the loads panel, you will create a ground loop between the loads panel and the main panel. This happens only when the inverter is in bypass mode. This is undesirable and very dangerous.

To avoid the N/G loop. Run a neutral from the main panel to the loads panel. This neutral is already bonded at the main panel, and provides short protection at the loads panel.
But, this puts the AT in parallel with the grids transformer.
This is undesirable, because the AT can try to carry the loads of the grids transformer.

To solve all of these issues, this is what I have done.

1) I ran a neutral conductor from the main panel to the loads panel. (Not bonded at the loads panel)
This provides a neutral for the loads in bypass mode. And provides the N/G bond from the main panel, in all modes.

2) install a relay on the AT feed conductors. Which is controlled by the inverter grounding relay. To only turn on the AT in battery mode.

To access the inverter grounding relay signal, I connected to the board at the screw location that was designed to ground the output "N" in battery mode.
This was done by a ring terminal and a non conductive nylon 3mm machine screw.
And another ring terminal at the internal "L" terminal. This gives me a 240v signal.

Now, the AT is never connected to the loads at the same time as the grid. (No load sharing)

And, the loads panel neutral is always bonded. (From the main panel's N/G bonding point)

I also added another relay between the inverter grounding relay signal and the AT relay.
This keeps the internal inverter power isolated from external power. (This was for my own piece of mind)

Did your SPF5000 have a screw in the grounding hole? The newer ones from Signature Solar have the screw present but don't seem to have any ground signal present at that location. (in other words this may not work with the newer models)

 

[timselectric]

I didn't buy mine from Signature Solar. They were out of stock and I didn't know that there were two different versions at the time. All of the ones that Signature Solar has sold, already have the screw removed at the factory. And I believe that there's some type of silicone application. So, I'm not sure if it will be easy to access the threads through the board. In my case, I actually removed the board and the stand-off behind it. Then I used a nylon nut on the back of the board.

 

[Trip.Diamond]

I didn't buy mine from Signature Solar. They were out of stock and I didn't know that there were two different versions at the time. All of the ones that Signature Solar has sold, already have the screw removed at the factory. And I believe that there's some type of silicone application. So, I'm not sure if it will be easy to access the threads through the board. In my case, I actually removed the board and the stand-off behind it. Then I used a nylon nut on the back of the board.

That is what I suspected. The newest ones from Signature Solar actually have the screw present. (I own one of the new ones...)
Now I will have to decide if its worth voiding the warranty to see if there is any ground signal present or it they simply removed the relay.
As it was Growatt itself that modified these units I have suspicion that the relay was simply removed.
Thanks for post!

 

[timselectric]

I wasn't aware of a change in models. It hasn't been mentioned anywhere that I know of. I'm curious to what was actually changed, now. The N/G relay was originally to the left of the screw. I'm not sure why they would go through the trouble of changing anything. The simple screw removal, solved the issue. I just wish that they would change the sticker and "N " markings. To show that it is a US version. This would cut down on a lot of the confusion.

 

[Trip.Diamond]

I wasn't aware of a change in models. It hasn't been mentioned anywhere that I know of. I'm curious to what was actually changed, now. The N/G relay was originally to the left of the screw. I'm not sure why they would go through the trouble of changing anything. The simple screw removal, solved the issue. I just wish that they would change the sticker and "N " markings. To show that it is a US version. This would cut down on a lot of the confusion.

Could not agree more on the proper labeling!
With a relay present in the system already and Growatt making its own Autotransformer it would be the simpilist thing for them make a system that was fully compliant with the North American grid. Just a Com Cable from Inverter to Autotransformer and add the relay to the autotransformer.

 

[timselectric]

Could not agree more on the proper labeling!
With a relay present in the system already and Growatt making its own Autotransformer it would be the simpilist thing for them make a system that was fully compliant with the North American grid. Just a Com Cable from Inverter to Autotransformer and add the relay to the autotransformer.

That would be the solution, that I would like to see implemented. But, would require buying their auto transformer.

 

[Cheap 4-life]

Where are the signal wires coming from that are on the bigger relay in the loads panel? From the inverters grounding relay signal/screw and from inverters L? In the pic it looks like the signal wires are attached to the load panels main lugs

 

[timselectric]

Where are the signal wires coming from that are on the bigger relay in the loads panel? From the inverters grounding relay signal/screw and from inverters L? In the pic it looks like the signal wires are attached to the critical load panels main lugs

That relay is getting power from the loads panel. And controlled by the extra relay I added to separate inverter control power from all other power. (The ice cube relay in the bottom left of the inverter.)

 

[Cheap 4-life]

That relay is getting power from the loads panel. And controlled by the extra relay I added to separate inverter control power from all other power. (The ice cube relay in the bottom left of the inverter.)

If the cube relay is sending control power to the loads panel relay, then why are the control/signal wires wired to the loads panels main lugs. Shouldn’t those control/signal wires come directly from the cube relay and not be attached to the main lugs?

 

[timselectric]

If the cube relay is sending control power to the loads panel relay, then why are the control/signal wires wired to the loads panels main lugs. Shouldn’t those control/signal wires come directly from the cube relay and not be attached to the main lugs?

The power originates at the loads panel.
Goes through the ice cube relay.
And then back to the auto transformer relay.
The other side of the auto transformer relay is connected to the other side of the loads panel power.
The internal inverter grounding relay, controls the ice cube relay. And, the ice cube relay controls the auto transformer relay.
I hope that I have explained it well enough to understand.

 

[Cheap 4-life]

The power originates at the loads panel.
Goes through the ice cube relay.
And then back to the auto transformer relay.
The other side of the auto transformer relay is connected to the other side of the loads panel power.
The internal inverter grounding relay, controls the ice cube relay. And, the ice cube relay controls the auto transformer relay.
I hope that I have explained it well enough to understand.

You probably have explained it well enough, just not for my slow brain.. I appreciate you taking the time to further explain.
So coming into the cube relay are wires from the loads panel which will go to the AT? The other 2 wires connected to the cube relay, are the control wires from the inverters grounding relay and L, which are to open/close the wires that allow the AT to work?

 

[timselectric]

You probably have explained it well enough, just not for my slow brain.. I appreciate you taking the time to further explain.
So coming into the cube relay are wires from the loads panel which will go to the AT? The other 2 wires connected to the cube relay, are the control wires from the inverters grounding relay and L, which are to open/close the wires that allow the AT to work?

Yes, exactly.

 

[Cheap 4-life]

Yes, exactly.

Ok so now im trying to understand the extra relay and why/how it’s wired differently

 

[timselectric]

The auto transformer relay is normal closed. And the ice cube relay closes the circuit to turn off the auto transformer.
I wired it this way, so that if it fails, the auto transformer is on. This way, I make sure that I am not left without a neutral.

 

[Trip.Diamond]

I didn't buy mine from Signature Solar. They were out of stock and I didn't know that there were two different versions at the time. All of the ones that Signature Solar has sold, already have the screw removed at the factory. And I believe that there's some type of silicone application. So, I'm not sure if it will be easy to access the threads through the board. In my case, I actually removed the board and the stand-off behind it. Then I used a nylon nut on the back of the board.

Well I bit the bullet... opened up the Newer one from Signature Solar. It has the screw in place and that screw is tied to ground at all times. Oddly enough it does have the relay present. Hooked up both Grid and Battery power to it and switched between both no change at the screw location. With or without the screw. Again oddly it reads approx. 120v between any L1 or L2 point in the unit. That's with or without a ground wire attached! Now I think it could be a firmware/software change that simply no longer activates the relay. This will take some more investigating to see what is really happening.

Just felt since I decided to open it up I should at least let everyone know this fix WILL NOT work on the newer models from Signature Solar (the ones being referred to as 'US' models) At least not as laid out here.

Because the Relay is still present it could be a different point on the board still has the needed signal or it could just be a firmware change would allow this method to work, but I will have to investigate further.

 

[timselectric]

has the screw in place and that screw is tied to ground at all times.

This is the correct screw?
All other screws are always grounded.

Again oddly it reads approx. 120v between any L1 or L2 point in the unit.

This is expected from a digital meter. You are seeing potential voltage. Which is generally about half the nominal circuit voltage.

Now I think it could be a firmware/software change that simply no longer activates the relay

This is very possible.
Thanks, for the information.

 

[Cheap 4-life]

Ok so when the N/O cube relay gets signal/control from the inverters ground relay it closes then allowing the N/C load panel/AT relay to open which stops the AT from working?
So then why the need for signal/control wires from the main lugs in the load panel to the load panel/AT relay?

 

[Trip.Diamond]

This is the correct screw?
All other screws are always grounded.


This is expected from a digital meter. You are seeing potential voltage. Which is generally about half the nominal circuit voltage.

This is very possible.
Thanks, for the information.

Yep it is the correct screw. The same one everyone it pointing to in the pictures.

I was using a analog tester which I thought would read the potential between L1 or L2 to Gnd which usually will read like 170v or 70v or something like that (a split voltage) but i suppose it being an inverter the circuits will even them out. I don't have much experience working inside Inverters. Its always good to learn new things!.

 

[timselectric]

Ok so when the N/O cube relay

N/C

The internal N/G relay closes and provides 240v to the normally closed ice cube relay. Which opens the control circuit for the auto transformer relay. Normally closed Auto transformer relay then closes , and turns on the auto transformer.
The ice cube relay was only used. Because, I didn't want to take internal inverter power outside of the inverter.