Grounding my Off-Grid Solar EV Charger

[TheDoctorUSA]

Hi everyone!

I've been lurking for a while trying to study how to ground my system, and I have come to different conclusions, after reading how other people grounded their systems, I had more questions than before.

My system is as follows:

Trailer on land with 5kw of solar panels on it.
Metal shed next to the trailer, it will house a sungoldpower 10kw, and a Yixiang 16kwh battery.

I will not use an actual panel, since I do not have those needs, rather, I bought a small outdoor panel with a 50amp breaker and a NEMA 14-50 (do not worry, I am switching the outlet that comes with the panel with a Leviton rated for continous EV Charging) and a 20amp breaker with a GFCI outlet.

I am under the impression that the Sungoldpower 10kw does NOT have a neutral ground bond (but I will check for continuity when I first turn it on).

If it doesn't, does that mean I will have to bond neutral and ground in my outdoor little panel?

As for grounding this, is there any way 2 or 3 4ft grounding rods will work? I am on gravel and not sure I can drive a rod for 8ft.

If I had to put 3 grounding rods, I would do as follows:

1) Bond all the solar panels frames together
2) Bond frames to sungold inverter chassis
3) Connect sungold to first ground rod
4) Connect first ground rod to second one, and connect second to third

I also see people "floating" and not having a ground at all, but I believe my Tesla charger would not let me charge if I did that, and it would also be dangerous if a live wire were to come in contact with any metal parts.

I am looking forward to everyone's input on this, I know it has probably been asked a million times, but I hope I will still get some help!

P.S. the only things I am planning to do with my system are: 20amp outlets probably just connected to a fan in the shed, 50 amp NEMA 14-50 connected to either my trailer, or tesla charger.

 

[BaylentheSky]

I’m not sure why you would need 2-3 grounding rods. All you need is just one. Since you already have a ground wire from your solar panel array connected to the inverter ground, you can then wire from the inverter’s dedicated PE connection to the grounding rod. This is mostly meant to dissipate any static electricity from the panels and inverter to the earth.

A bonded neutral/ground would be a separate issue from earth grounding your trailer setup, which I think you’re already aware of. You would have to check with the user manual to see if it is physically bonded at the inverter or is manually/automatically enabled via software setting. Also, depending on the EV, some may not even require the charging source to be bonded at all. Have you tested charging your EV as is?

As always, if you’re earth grounding your inverter, do not connect it to your home, or you would have a ground loop.

 

[TheDoctorUSA]

Hey @BaylentheSky thank you so much for the fast reply.

I was asking for the 2-3 grounding rods because I am worried just ONE 4 ft grounding rod will not be enough or will not reach a good conductive depth, do you think it will be fine?

As for the neutral-ground bond, yes I understand that would be separate, I was trying to get as many questions answered as I could lol!

I will connect everything and check if my inverter has a neutral ground bond already active or if maybe it's just a screw to drive in, I looked in the manual but don't see anything mentioning it.

And yes, I can definitely test the Tesla charger and see what it says, but I'm guessing even if it allows me to charge without the bond, I should still have one, for safety.

Also, thank you for the reminder, I definitely do not want any ground loops, the inverter will not have AC IN ever connected, only AC OUT.

 

[BaylentheSky]

If you can post its model number here, people could help you look into its ground/neutral bond setting.

As I mentioned previously, this trailer setup does not need more than 1 ground rod, and it doesn’t have to be that long, although length is important to ensure that the rod has penetrated through enough moist soil to dissipate excess current built up in the form of static electricity. The top layer of soil is usually dry, so a ground rod (or 2) from your house’s main panel needs to be at least a certain length since it is connected to ALL devices big and small in your house which can all build up some substantial current over time without somewhere to discharge. Your trailer setup is not connected to that many devices, you don’t need a rod that deep, but obviously just my opinion and it’s always better to overkill everything. I would just use what I already have, and I think a 4ft rod would suffice.

 

[TheDoctorUSA]

Thank you!

I should probably mention the rod is 3/8 inches and not 5/8 like other usual ground rods, but hopefully it will suffice.

My inverter model number is SPH10048P

 

[BaylentheSky]

I tried Googling but could not find any info on this inverter’s neutral/ground bond. An easy way to check is to turn it on then check for voltage between L1 and G, if it shows 120V that means the inverter N/G are bonded.

 

[TheDoctorUSA]

Thank you so much for your help.

That makes sense, because if G is bonded with N you can complete the circuit so one hot would show 120V. Thank you! Learned a lot today.

 

[TheDoctorUSA]

Hey @BaylentheSky !

I was about to make a new thread but figured you might be able to help me with this.

I received everything minus my little outlet panel and some reflectix for inside the shed (hoping it doesn't get too hot in there) so I'm almost ready to start assembling everything!

This is what I came up with for grounding, I'm pretty sure this is called an "AC and DC ground".

My panels would all be bonded together with some copper wire (I have 6 AWG), then I would bring the copper wire up to the inverter and bond it with the chassis, using a little grounding screw that comes on the inverter.

I would then connect the ground bus bar from the outlet panel to the grounding rod.

Do you think this will work?

Attached a picture for it:

 

[BaylentheSky]

You obviously did your homework, nothing I can add. Good luck with your system!

Edit: 2 AWG THHN wires have an open air (not inside conduit) rating of 140A, which comes to about 7300W. If I were you, I’d limit charging your EV to 7200W (30A AC) to stay safe, and keep your inverter from constantly working near max capacity, thus enhances its longevity.

Edit 2: I’m blind. You said 2/0, I thought 2 AWG.

 

[1ufvlsi6x]

Don't forget to connect all the grounding rods of the wider system together otherwise you will cause currents through your devices when grounding is actually needed. Other than that the grounding cables must be big enough (there are regulation codes for that).

Grounding confused me for the longest time in terms of the path it must "first" take; but I learned the paths are irrelevant when we're not talking about neutral-grounding; if it's about grounding in itself: just continuity is needed and big enough wires.

 

[TheDoctorUSA]

You obviously did your homework, nothing I can add. Good luck with your system!

Edit: 2 AWG THHN wires have an open air (not inside conduit) rating of 140A, which comes to about 7300W. If I were you, I’d limit charging your EV to 7200W (30A AC) to stay safe, and keep your inverter from constantly working near max capacity, thus enhances its longevity.

Edit 2: I’m blind. You said 2/0, I thought 2 AWG.

Thank you so much, that comment made me happy! I definitely researched this a lot and wanted it to work well.

Also, little off topic but still wanted to update you about my situation:

I had originally planned on putting my inverter in a walmart metal shed I put outside (sitting on gravel with no floor). After looking at the humidity levels at night (over 90%) I decided that I needed to invest to make it safer for the inverter and battery (which are both NOT outdoor rated).

I am officially building a 8x6 shed floor with 2x4 and 4x4 treated lumber (approved for ground contact), moisture resistent foamboard and pressure treated plywood. After that, I will use some closed cell spray foam on the inside and hopefully insulate the walls a little.

For when night comes, I should be good because the inverter releases heat and the shed inside temperature should not drop as drastically.

Only problem I can find with this, once summer comes I will have to figure out a way to keep the temps lower (I live in SoCal).



Thanks again for your help and I will keep you in the loop.

 

[TheDoctorUSA]

Don't forget to connect all the grounding rods of the wider system together otherwise you will cause currents through your devices when grounding is actually needed. Other than that the grounding cables must be big enough (there are regulation codes for that).

Grounding confused me for the longest time in terms of the path it must "first" take; but I learned the paths are irrelevant when we're not talking about neutral-grounding; if it's about grounding in itself: just continuity is needed and big enough wires.

Thank you for the reply.

Could you expand on the "paths" for neutral bonding? What do you mean by that?

I was planning (in case my inverter does NOT neutral bond already) to just jump neutral and ground at the panel (where my 50amp and 20amp breakers are for the outlets)

 

[BaylentheSky]

Some people think it's overkill, but I put a portable AC unit into my shed, and program it to run between 12 and 4 pm every summer. It does get hot where I live (also SoCal, but not near the coast, so it can get well into the 90's in the summer). If you have an insulated shed, you may even get away with less than 4 hours in run time.

Really cool to see your commitment. Sorry you got bit by the solar bug. You're now one of us

 

[1ufvlsi6x]

Could you expand on the "paths" for neutral bonding? What do you mean by that?

I was planning (in case my inverter does NOT neutral bond already) to just jump neutral and ground at the panel (where my 50amp and 20amp breakers are for the outlets)

I mean in the case neutral bonding is not in the discussion, any grounding rods of the property must be connected to each other,
and there's obviously no need to care what will connect "first" to the panels/inverter/each other since they will have direct continuity anyway.

PS obviously with the right cables, eg you can't connect panels with subpar gauge to old ground and then put the proper gauge from a new ground to the old ground etc.

 

[TheDoctorUSA]

Some people think it's overkill, but I put a portable AC unit into my shed, and program it to run between 12 and 4 pm every summer. It does get hot where I live (also SoCal, but not near the coast, so it can get well into the 90's in the summer). If you have an insulated shed, you may even get away with less than 4 hours in run time.

Really cool to see your commitment. Sorry you got bit by the solar bug. You're now one of us

Thank you!

Little update: today I built (With the help of my grandpa in law) my shed flooring, 4x4 runners on the bottom (ground contact approved), 2x4 frame with 16inches rafters and foam board insulation in between, pressure treated plywood on top and then finally my cheap metal shed on it lol.

I also built a nice frame for my inverter!!! And it's finally hooked up on it, so tomorrow I will try to finish assembling the Yixiang and then hook everything up.

The last thing I need is do some closed cell spray foam on the inside of the shed... Put a fan in it, and once summer comes I'll figure out if I need a little portable ac.


'

 

[BaylentheSky]

Ahem, when you're done with that, I know a guy that needs a floating deck built

 

[TheDoctorUSA]

Lol it was actually super easy to build, it was my first time working with wood and I loved making it. Hit me up!!! We'll do a solar reunion... I'll bring some pulled pork