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Old 11-30-2019, 02:50 PM   #1
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Grounding Wire for Inverter 12 volt/3000 watt

I'm installing solar and a new inverter/charger. What size should the grounding wire be?

I read some searches online that I should use the same wire size I have connected to the battery. I'm using 2/0 gauge doubled up. That seems like a massive ground wire though I'm a newbie.
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Old 11-30-2019, 03:20 PM   #2
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Ground wire? If you mean the negative wire that runs back to the batteries from the inverter, then yes, Same gauge as the positive.
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Old 11-30-2019, 03:53 PM   #3
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No he means ground wire, a wire from inverter case to chassis for ground.

That wire should be 12 or 10 gauge, depending on the size of the 120 volt wires you use.
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Old 11-30-2019, 05:57 PM   #4
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On a 3000w inverter system, for example Magnum MSH3012M, these are the wires related -
(1) Positive cable between the battery and inverter, 4/0 recommended, 2/0 practically ok (at your own risk).
(2) Negative cable between the battery and inverter, same size as above.
(3) Negative grounding cable between battery and chassis. Same size as (1). On some RVs, the negative able (2) is composed of 2 sections - first section is from battery to chassis, immediately the second section starts from this spot on to inverter. In this case, (3) is no longer necessary.
(4) Hot wire(s) from main distriution panel to inverter carrying 120v AC, mostly 10g, 30A. On some RVs, there could be two hot wires, red and black.
(5) Neutral wire from main panel to inverter same size, typically white.
(6) Ground wire from main panel to inverter same size, mostly bare copper.
(Note: (4) (5) (6) are likely in Romex 10/3 or 10/2)
(7) Hot wires from inverter to subpanel 120v AC, mostly 2 wires, red and black, 10g or 12g or 14g dependent upon individual coach electric configuration.
(8) Neutral wire from inverter to subpanel same size to the thickest one in (7).
(9) Ground wire from inverter to subpanel same size to the thickest one in (7).
(Many RVs don't have a subpanel, as the existing inverter has built-in circuit breakers for outputs.)

Good luck on your build.
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Old 11-30-2019, 11:45 PM   #5
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I'm still confused. One person thinks 10 or 12 gauge wire depending on size of 120 volt wire. Another says to use the same size as I used between inverter and batteries which I used 2/0 gauge doubled up.

I have a Victron Multiplus 12/3000. I'm now questioning if I have to ground my MPPT. I bet you guys hate newbies on here.
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Old 12-01-2019, 05:53 AM   #6
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I would first read the installation manual. If this were a Magnum 12/3000, I believe they recomending 4/0 doubled for battery ground and chassis ground for runs under five feet long. Over five feet, not recommended. If it,s not in the istallation manual, I would call their tech support. Good luck.
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Old 12-01-2019, 07:49 AM   #7
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As stated it depends on which ground wire you are speaking of and you have not made that clear. If it is part of the circuit that powers the inverter from the batteries, IE goes to the largest terminals on the inverter, it should be the same size as the positive wire. If it goes anywhere else it should be the same size as the 120v wiring leaving the inverter. You have three possibilities for grounds. One large for 12v power input, one smaller for 120v power output (typically romex bundled with the hot and neutral), and one smaller for inverter case ground (typically all alone).
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Old 12-01-2019, 10:37 AM   #8
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Newbies are welcome, that's why we are here. However, installing an inverter and solar does require a basic understanding the principle of electricity, regardless 120v or 12v. To answer your specific question of ground wire, we do need to know which grounding you are talking about. I was expecting you could find the answer by picking one from the wires/cables on post #4.

Considering the potentially catastrophic consequences of wrong doing, if it's somewhat challenge to you, you might want to check with AM Solar in Eugene, OR, or an experienced installer in your area.

As for MPPT box grounding, depends. I am using two of them, one 96a, another 60a. One has a grounding screw, another doesn't. It never hurts to ground it.
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Old 12-01-2019, 10:46 AM   #9
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case to frame ground wire is #12 CU
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Old 12-01-2019, 11:38 AM   #10
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I'm referring to grounding case to frame. I must be misunderstanding the manual when it says to use the same size as the battery wires when grounding. I am using the same size on positive and negative runs. I was going to use the grounding cable already connected to my current 1000 watt inverter and wire in a grounding busbar for other items. I assumed that would work. Then I started reading the manual and online research and I got confused. I did not see anything in the manual about wire size on grounding the case to frame. I was going to call the retailer on Monday though I wanted to get the grounding done this weekend and I don't like redoing things so I thought I would ask you guys. It sounds like 10 or 12 gauge would work and I'm thinking my current ground is good to go.

I am using 2/0 gauge doubled up for positive and negative runs to the battery which is suppose to be acceptable up to six meter runs. That's what the manual said and I confirmed that with the retailer. And what I read supposedly doubling the 2/0 wire is better than just using one single 4/0 gauge. I've only came across one YouTube video showing the person doubling 2/0 gauge wire for their install. I'm learning, maybe slowly.
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Old 12-01-2019, 12:53 PM   #11
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The answer from cavie is the right one :-)
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Old 12-01-2019, 08:43 PM   #12
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Have never owned a Victron inverter. But if it's similar to Magnim MS series, Magnum doesn't have a separate case to chassis grounding. Inside the box, there is a grounding terminal as part of connection block, which is connected to the case. What one needs is just to plug in the grounding wires from main panel and that to the subpanel, and tighten up the screw, it's all set.

That you plan to use the ground cable for 1000w inverter as a grouding on your new system might be problematic, too thin. You'd better follow the manual to change it to the same size as inverter cables (double 2/0).

According to American wire gauge chart, the section area of double 2/0 is greater than that of single 4/0, hence double 2/0 is preferrable.
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Old 12-02-2019, 01:50 PM   #13
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Quote:
Originally Posted by CountryFit View Post
Have never owned a Victron inverter. But if it's similar to Magnim MS series, Magnum doesn't have a separate case to chassis grounding. Inside the box, there is a grounding terminal as part of connection block, which is connected to the case. What one needs is just to plug in the grounding wires from main panel and that to the subpanel, and tighten up the screw, it's all set.

That you plan to use the ground cable for 1000w inverter as a grouding on your new system might be problematic, too thin. You'd better follow the manual to change it to the same size as inverter cables (double 2/0).

According to American wire gauge chart, the section area of double 2/0 is greater than that of single 4/0, hence double 2/0 is preferrable.
My Magnum inverter has a ground terminal and has a wire attached to the chassis frame. Number 7 in the attached diagram.
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Old 12-02-2019, 02:06 PM   #14
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Mine also, with the chassis ground from the MSH3012H.
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