Grounding Sanity Check

[Thersom1948]

Hi all,

I'm hoping @FilterGuy could review, since it is all based on his guides, but if anyone else could help that would be much appreciated!

I have read all of the grounding guides. and the Inverter Grounding Schemes. I am just hoping for a quick sanity check

1. I have a Growatt 24V SPF 3000TL LVM (Old Version)

2. I have a completely floating solar generator system (Will's "Handcart" style) with Eve cells and Overkill Solar BMS. Not in a vehicle.

3. I charge it from Non-GFCI shore power occasionally, but is not permanently installed.

4. I charge it from Honda EU2000i occasionally, but is not permanently installed

5. If/when power is out for a long time, I would charge it with solar panels, but are not permanently installed

After reading all of those guides my takeaway for ground safety are that I should:

A. Jump the AC-in and AC-out Neutral inside the Growatt (see attached pic with proposed jumper)

B. Use a Neutral/Ground plug adapter specifically and only for the Honda<>Growatt charging

C. If deploying solar panels, Bond all Panels and Growatt case to a single Earth ground. All Completely Off-Grid

Is that correct?


D. Bonus question: The guide says the Growatt has zero AC Ground/Neutral bond. Is that a safety risk for running the AC loads from the inverter when it is not connected to grid (or Honda with N/G plug)? Do I need to run all invert AC loads from the Neutral/Ground plug adapter too?

Thank you!

 

[FilterGuy]

C. If deploying solar panels, Bond all Panels and Growatt case to a single Earth ground. All Completely Off-Grid

Is that correct?

You were doing well till you hit 'C'. I would tie them back to the inverter ground.

If I am following your description. It is a portable system with no earth-grounding electrodes. This means your AC is floating.... as are most portable systems. That by itself is not a big issue. It is not ideal but I would not worry about it.

However, I would want to have the system clear ground faults (The hot wire touches a ground wire or metal the ground wire is connected to.
(Some people say that for a floating system like you have, this is not necessary, but I am not comfortable with that)

1. I have a Growatt 24V SPF 3000TL LVM (Old Version)

My understanding is the the Growatt does dynamic bonding. If it does, you should be good to go with what you describe:

* When plugged in the NG bond is provided by the house
* When on Generator the NG bond is provided by the Bonding plug.
* When no AC-in is present the inverter should generate an NG Bond.


Please do this: With the inverter totally powered down and nothing connected to the AC input or output ports, measure the resistance between the Neutral Output and Ground Output. If it is nearly zero ohms, you have dynamic bonding.

 

[Thersom1948]

Thank you for the feedback!

If I am following your description. It is a portable system with no earth-grounding electrodes.

Correct.

Testing the Growatt completely disconnected from everything, powered off, no battery, nothing:

in-G to out-G: Continuity
in-N to out-N: No continuity

in-N to in-G: No continuity
out-N to out-G: No continuity

* When no AC-in is present the inverter should generate an NG Bond.

My Growatt is several years old - purchased in 2020. See attached pic with P/N.

My understanding from your other threads and Inverter Guide is that this unit is from quite a while before they added the internal dynamic bonding, but I might be misunderstanding

Does it need battery power (even while Inverter is turned off) for this to be active?

I would tie them back to the inverter ground.

What is the Inverter Ground in this situation? The inverter chassis? So just run a suitable ground wire from the panels back to the Inverter chassis along with the panel power wires?

Thanks!