Neutral ground screw

[johnskdyvn]

I'm almost there ! Thanks to every one of you experts on this site i'm going to start installing most of my solar setup this weekend. I do have a question about using the green bonding screw in my panel though.

I am TOTALLY offgrid. I'll be setting up my Growatt 3000 48v inverter this week. I am NOT going to have an "AC in" connection (only AC out). I will be running my AC out wire to a small 100 amp distribution box. I'll only be running 3-4 lines from it (cabin, shed, chicken coop, and some lighting). As I have NO main panel (just the inverter and the small 6 circuit breaker panel), am i supposed to install the grounding screw into the panel? Most of what i watched says as long as my main panel is neutral ground bonded, then i don't need to do that to my subpanel. That being said, my subpanel is actually the only distribution box i'm using.

I thought i read that the Growatt inverter already had a grounding screw inside of it. If true, would this alleviate the neutral ground bond screw that came with my panel? So far, I have run the ground wire to the distribution box. I'm just unaware of having to use that bonding screw?

Also, as stated before, my cabin is offgrid. i don't believe it has a ground rod to the cabin. I always ran the generator to the cabin to power it. I have read that an outbuilding needs 2 ground rods. Is this true, or can i use just the one i ran the other day?

Thank you all in advance. Your knowledge is helping me learn quite a bit.

Johnny

 

[12VoltInstalls]

am NOT going to have an "AC in" connection (only AC out). I will be running my AC out wire to a small 100 amp distribution box

always ran the generator to the cabin to power it

Will you be using the generator to charge, ever? Like cloudy weather etc.?

have NO main panel (just the inverter and the small 6 circuit breaker panel),

you should use one of the six breakers for a 25A ‘main’ breaker, and use the remainder for loads.

am i supposed to install the grounding screw into the panel? Most of what i watched says as long as my main panel is neutral ground bonded, then i don't need to do that to my subpanel. That being said, my subpanel is actually the only distribution box i'm using.

Hoo boy. There it is again.
Neutral-ground bonding. @timselectric

What does the growatt instructions say?

If the screw is removed so neutral out of the growatt truly is floating, then bonding in the distribution/subpanel is required and crucial. (That is how I would prefer to do it.)
Run the neutral from the growatt “out” terminals to the subpanel and bond it there. The white/neutral from the growatt will be bonded at the subpanel /distribution panel to complete the ‘main’ breaker circuit to trip in a fault. Those will need to be minimum of 10ga wire.
Having said that ground is supposed to be derived at the source of power which is in the growatt. I hope for an electrician to join in and say what proper thing to do but if not bonding in the subpanel you will need an insulated/isolated busbar in the subpanel. Most retailed subpanels include one.

I’m not an electrician but a “ground rod” into dirt is not required to make the circuits function and be safe. Some code interpretations in different jurisdictions say to run a ground rod- but it isn’t functionally necessary.

Either way- if using the generator ever is a possibility then you need to assure its neutral is open/floating/not bonded on the generator and that it does bond neutral from the house bonding point when connected.

I'm just unaware of having to use that bonding screw

I’m totally unfamiliar with that unit so I’m not the right guy to answer and have considered deleting all above but I’m leaving it. If I’m wrong I’ll surely be corrected and will learn something

I have that unit ‘bookmarked’ and have considered researching it’s appropriateness in my circumstances but hadn’t pursued much because I read some that claim it has nearly 100W of idle consumption which is way too much overhead for my liking.

 

[timselectric]

A single ground rod is enough. But two are required to pass an inspection. (If needed)
With the Growatt off, test for continuity between output ground and neutral.
If you have continuity, don't bond the panel.
If you don't have continuity, bond the panel.