Can I connect my inverter chassis ground wires to the closest chassis point?

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
333
I have my inverter chassis ground wires running back to the negative bus bar which ends up connected to chassis through the shunt. Is there any reason why I cannot connect my 4 ga chassis grounds for each inverter directly to the chassis where they are mounted? Would tidy things up a bit on my negative bus bar and eliminate 2 large wires running back to the battery compartment.

DC wiring 290RL.jpg
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
Depends on whether you mean the actual negative power carrying wire or a green wire/AC voltage 'ground':
And if its marine, but I assume its not.

If its the black "negative" DC power wire:
You should run it to the bus bar period. If possible do this for everything.
You CAN go to the chassis, but you WILL cause minor issues that will get worse over time and MIGHT have major issues up front.
Strongly suggested to not do this. You might also experience nasty ground loop interference with your radio.
You will likely also create a galvanic charge differential causing increased corrosion of the chassis but its less of an issue for non-marine stuff.

If you are referring to the green/ground wire for the AC voltage system:

Depends if you are in the US or certain areas of the world with actual regulations on where that can be hooked up.

US:
Send it however you want but the above suggestions apply to this ground wire as well.

UK:
I believe its code to tie the chassis grounds to a dedicated AC ground point separate from the DC stuff with a clear label.
(And I believe this is dumb per above reasons but the code is aimed at the lowest common denominator)

I had this conversation with a few UK folks on facebook more than once.

If its marine, the whole thing is another topic and we should involve an expert on this for many safety and galvanic reasons.
 

circus

Solar Addict
Joined
Jul 8, 2021
Messages
271
Good question. On a van, I have the 12v inverter bonding, negative feed, ac gd and house batteries grounded to the chassis. Not to mention the systems of the van. Everything works. Am I missing something?
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
Good question. On a van, I have the inverter bonding, negative feed, ac gd and house batteries grounded to the chassis. Not to mention the systems of the van. Everything works. Am I missing something?
Do you disconnect the bond when on shore power?
 

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
333
Depends on whether you mean the actual negative power carrying wire or a green wire/AC voltage 'ground':
And if its marine, but I assume its not.

If its the black "negative" DC power wire:
You should run it to the bus bar period. If possible do this for everything.
You CAN go to the chassis, but you WILL cause minor issues that will get worse over time and MIGHT have major issues up front.
Strongly suggested to not do this. You might also experience nasty ground loop interference with your radio.
You will likely also create a galvanic charge differential causing increased corrosion of the chassis but its less of an issue for non-marine stuff.

If you are referring to the green/ground wire for the AC voltage system:

Depends if you are in the US or certain areas of the world with actual regulations on where that can be hooked up.

US:
Send it however you want but the above suggestions apply to this ground wire as well.

UK:
I believe its code to tie the chassis grounds to a dedicated AC ground point separate from the DC stuff with a clear label.
(And I believe this is dumb per above reasons but the code is aimed at the lowest common denominator)

I had this conversation with a few UK folks on facebook more than once.

If its marine, the whole thing is another topic and we should involve an expert on this for many safety and galvanic reasons.
It is neither. The black negative DC power wire is 2/0 and runs to the negative bus bar. The AC ground is connected via the AC inputs and outputs. The wire I am talking about connects to the case of the inverter via an external lug.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
It is neither. The black negative DC power wire is 2/0 and runs to the negative bus bar. The AC ground is connected via the AC inputs and outputs. The wire I am talking about connects to the case of the inverter via an external lug.
It can't be neither.

Its either a negative power lead or its an AC ground wire. Based on this post, its the second thing. The chassis ground and the "AC ground" as you phrased it are one in the same and you should find continuity between any one of your outlets' ground pins and the case of the inverter.

This means you fall under the second scenario I described.

I am not sure why you need 4awg chassis grounds that don't carry current but I know some models specify this.
 

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
333
It can't be neither.

Its either a negative power lead or its an AC ground wire. Based on this post, its the second thing. The chassis ground and the "AC ground" as you phrased it are one in the same and you should find continuity between any one of your outlets' ground pins and the case of the inverter.

This means you fall under the second scenario I described.

I am not sure why you need 4awg chassis grounds that don't carry current but I know some models specify this.
I agree. The Xantrex manual actually says I should use 1/0 (one size smaller than 2/0). But it says the minimum is 8ga bare copper.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
I understand the reason behind it though. It's just fairly unlikely to occur. Bigger wire is always more gooder so it is what it is.
 

circus

Solar Addict
Joined
Jul 8, 2021
Messages
271
Do you disconnect the bond when on shore power?
Why would I do that? We must be talking about different subjects. The closest thing to shore power, I might do, is hooking up a battery charger.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
Why would I do that? We must be talking about different subjects. The closest thing to shore power, I might do, is hooking up a battery charger.
When "bonding" an inverter there are different requirements for bonding when on or off shore power. Its a safety issue. Some inverters do this internally and manage the connection automatically.

But if you are just on a battery charger you are good to go.
 

Zil

Just another ass on the web
Joined
May 27, 2020
Messages
1,339
On a van. IF the negative chassis connection points are proper cleaned and protected from corrosion then the "case ground lugs" can be connected any place on the chassis as long as your chassis is part of the negative ground plane. Follow the recommended wire awg posted in your manual.
 
Last edited:

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
On a van. IF the negative chassis connection points are proper cleaned and protected from corrosion then the "case ground lugs" can be connected any place on the chassis as long as your chassis is part of the negative ground plane. Follow the recommended wire awg posted in your manual.
While this is true, it's really bad practice and virtually no mobile power system manufacturers suggest it.
 

Zil

Just another ass on the web
Joined
May 27, 2020
Messages
1,339
Why is it bad practice? Do you have a link to a manual with a statement against the practice? I refer you to this part of my post; "IF the negative chassis connection points are proper cleaned and protected from corrosion"
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
Even if they are cleaned and kept clean the chassis is a poor conductor. Steel sucks and the various weld points, paint, and other things combine with multiple current paths to cause ground loop interference, increase galvanic corrosion, and generally have much higher resistance than an appropriately sized cable.

Even the smallest difference in resistance can set up a potential voltage difference which is where the interference and galvanic issues can come from.

The only reason the auto industry does it is because the things they put to the chassis are low power, and saving just 1 cent per vehicle adds up to almost $1 million dollars annually in the global auto market.

Now imagine saving a hundred feet of wire that costs 5 cents a foot, per car.


An automaker doing it doesn't mean it's best practice or even good practice for that matter. It just means it works and lasts long enough to make it past the warranty.
 
Last edited:

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
As for a link to a manual...
Pick any victron diagram you'd like.
Edit: wrong screenshot.

Victron-Energy-1277x800.png
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
The only time you "should" ground the stuff separately is where code demands it.

This still causes potential interference issues, but code is code.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,820
I will reiterate though that you're technically not incorrect. It's just much less preferred in general is all in saying.

The system will work just fine. You may even never see an issue with a bit of luck.
 

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
333
This brings up another question from me. Why do I have a wire going from my battery negative terminal to the chassis? I'm not sure anything on my trailer uses the chassis as the actual negative current path. Everything I have found so far always has two wires running to it and both of those run all the way back to the DC distribution center. I may unhook the battery chassis wire and see if anything stops working. Just out of curiosity.
 

HRTKD

Boondocker
Joined
Apr 24, 2020
Messages
6,535
Location
Somewhere South of Denver
This brings up another question from me. Why do I have a wire going from my battery negative terminal to the chassis? I'm not sure anything on my trailer uses the chassis as the actual negative current path. Everything I have found so far always has two wires running to it and both of those run all the way back to the DC distribution center. I may unhook the battery chassis wire and see if anything stops working. Just out of curiosity.

This sounds like the wiring in my RV. Everything gets two wires. Nothing relies on the chassis ground except the big devices that need a ground. I did not run my battery negative to the chassis. I did however connect the ground lug on my inverter, MPPT, converter, etc, to a ground bus bar that then connects to the chassis.
 
Top