Ground wire size advice

[cORNhOLIO]

Hi, I have a very similar system setup to this one 400w solar with alternator charging except I have the 3000w inverter charger from Renogy which states in the manual to use 4/0AWG cable to the battery.
Reading online about ground wire sizes, everything seems to suggest to base it on max load potential so I assumed 4/0awg. However, my inverter manual says it can be grounded with 8awg.
Does this sound correct, it seems like I am missing something.

 

[Madco]

Take a look at NEC tables 250.66 and 250.122.

 

[Madco]

4/0 is too big, you won't be able to land it effectively. #10 copper is acceptable but if the manufacturer states #8, then use that.

 

[cORNhOLIO]

4/0 is too big, you won't be able to land it effectively. #10 copper is acceptable but if the manufacturer states #8, then use that.

Thanks for your help, that's great. I had a look at the tables you suggested and tbh, it's beyond my understanding. I am an engineer but not electrical, I will be getting all my work checked before I flick the switch but it's great to have some help getting it layed out first.

 

[justinm001]

Whoa I think there's some confusion. 4/0 gauge would be ideal for the positive and negative to the batteries. For grounding they're talking about frame grounding using the bolt in the image below. This is to ground the device to help minimize shock risk.

So 4/0 to batteries AND 8 gauge to the frame if its not bolted to the frame already.

 

[cORNhOLIO]

Whoa I think there's some confusion. 4/0 gauge would be ideal for the positive and negative to the batteries. For grounding they're talking about frame grounding using the bolt in the image below. This is to ground the device to help minimize shock risk.

So 4/0 to batteries AND 8 gauge to the frame if its not bolted to the frame already.


View attachment 161707

Thanks Justin, that makes sense. So what do you recommend for the ground wire from the negative busbar to the van chassis?

 

[justinm001]

As thick as possible but if all large grounds are home run then whatever you have extra is fine. As long as you can safely physically fit the wire ends on the devices you can't go too large.

 

[Madco]

Sorry, didn't intend to imply that 4/0 was too big for the supply ro the inverter, only that it was too big for the ground!

 

[cORNhOLIO]

As thick as possible but if all large grounds are home run then whatever you have extra is fine. As long as you can safely physically fit the wire ends on the devices you can't go too large.

I have metre of 1awg that I bought by mistake so will use that. Thanks again for your help.