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  1. #1
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    Solar and DC wiring

    Hi folks,

    Now that I have my panels mounted on the roof I have a few questions on my next step.

    Next time I am at my other house where I store my rig, I am going to do the solar wiring and battery install.

    So I have 10awg from the roof going into a dc 30amp cb. Then into the Victron 150/60 charge controller.

    From the charge controller I have a 60 amp cb going to the + bus bar using 4awg.

    Connecting the two Amperetime 300ah batts using 4/0 (will do buss bar if they come in time).

    From the battery bank plus using 4/0 to 400 amp t fuse, to cutoff switch, again using 4/0 to the bus bar.

    Using 4/0, buss bar to 400 amp ang fuse then to Victron Multiplus II.

    On the neg side of the batts using 4/0 to Victron Smart Shunt, then to neg DC bus bar.

    From bus bar to original dc cutoff switch then dc loads, just because I don’t want to leave a hole.

    What gauge wire should in use for frame ground on inverter?

    In think I have fused and isolated sufficiently. Just looking for additional eyes to keep me sane.

    Bill
    Last edited by Redapple63; 10-22-2022 at 04:40 PM.
    2019 GMC 3500 SRW Sierra Denali Duramax
    2020 Reflection 315RLTS

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    Quote Originally Posted by Redapple63 View Post
    What gauge wire should in use for frame ground on inverter?
    There's debate on the interwebs on whether or not you should ground the inverter the frame (bonding vs physical earth and hot skin, etc. and likelihood of internal failire) since you'd really need to drive a grounding rod every time you park to ground the chassis...

    Any who... Victron recommends same size cable as inverter to battery size or one size down. So in your case, 3/0 min but 4/0 preferred.

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    Solar and DC wiring

    Quote Originally Posted by A.Texas.Yankee View Post
    There's debate on the interwebs on whether or not you should ground the inverter the frame (bonding vs physical earth and hot skin, etc. and likelihood of internal failire) since you'd really need to drive a grounding rod every time you park to ground the chassis...

    Any who... Victron recommends same size cable as inverter to battery size or one size down. So in your case, 3/0 min but 4/0 preferred.
    Yes, I did read about that. 4/0 is pretty tough to route down below to the frame. That’s why I asked that question I think I will run the ground for the charge controller to the neg bus bar, and the inverter to chassis ground.

    Bill
    2019 GMC 3500 SRW Sierra Denali Duramax
    2020 Reflection 315RLTS

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    I really believe this is wrong or I'm not understanding what is being written.

    On the DC side, yes, they need to be the same size, power and ground. On the AC side, according to Victron, it needs to be 'The ground conductor should be at least 4mm²' [Pg 3].

    https://www.victronenergy.com/upload...s-II_GX-en.pdf

    From my understanding, the case is grounded so if there is a problem, you will not be shocked. This is for the AC side, the DC side is considered save with only 12V

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    Site Team Redapple63's Avatar
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    Quote Originally Posted by Butcher View Post
    I really believe this is wrong or I'm not understanding what is being written.

    On the DC side, yes, they need to be the same size, power and ground. On the AC side, according to Victron, it needs to be 'The ground conductor should be at least 4mm²' [Pg 3].

    https://www.victronenergy.com/upload...s-II_GX-en.pdf

    From my understanding, the case is grounded so if there is a problem, you will not be shocked. This is for the AC side, the DC side is considered save with only 12V
    Thanks Butcher!

    I don’t have the inverter yet so was absolutely planning on using the 4/0. So per the manual 4mm or approx. 6 gauge. Very different scenario.

    Thanks

    Bill
    2019 GMC 3500 SRW Sierra Denali Duramax
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    Quote Originally Posted by Butcher View Post
    I really believe this is wrong or I'm not understanding what is being written.

    On the DC side, yes, they need to be the same size, power and ground. On the AC side, according to Victron, it needs to be 'The ground conductor should be at least 4mm²' [Pg 3].

    https://www.victronenergy.com/upload...s-II_GX-en.pdf

    From my understanding, the case is grounded so if there is a problem, you will not be shocked. This is for the AC side, the DC side is considered save with only 12V
    There's a rabbit hole for sure. LOTS of discussion about this on DIY Solar and Victron's forum. And even Victron has conflicting answers...

    That excerpt is talking about true AC grounding, i.e. physical earth (in this scenario with an RV the ground is going to be from the pedestal). That is where the 4mm (12awg) comes into play. You would need to true PE connection (i.e. drive ground rod every time you were not on shore power). Then you have bonding to chassis which is what's being questioned here and where all the back and forth goes. I personally have bonded 12v to chassis via negative bus bar (like from factory but with 4/0), but I do not have the inverter chassis case separately bonded to the chassis. Although my inverters are mounted by screw to the chassis frame so technically... any who.

    If there was a component failure and somehow AC and DC shorted internally on the inverter, a 12awg cable would not be any where bear sufficient to carry that type of current, hence why it's suggested same size as DC or one size smaller because you qould be crossing AC and DC, potentially.

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    As I mentioned, I was a bit confused and thought it was about the AC portion.

    Not certain why a grounding rod was mentioned for the DC which is why I was a bit confused what was being discussed.

    I would have all the DC going through bus bars. If you have several batteries, they all do not need to be 4/0. The inverter that sounds like it would be the biggest consumer should be at least 4/0 to/from the bus bars. The batteries to the bus bars need to be sized with the loads they are expecting. Since you have two, neither will be delivering 300A. In simple terms, the would spread that 300A load to both batteries. So each battery would give 150A. Of course, that is pretty simple minded, but I hope you get the drift.

    If I recall, I sized my two batteries to 2/0 and the third will be sized the same. Each BMS is rated to 200A and is programmed to cut off at 175A. On paper, none of the batteries will deliver 300A by itself.

    I did not attach any additional ground to the frame and elected just to keep that wiring stock with the way GD has it.

    If somehow AC and DC shorted internally in the inverter, a 4/0 ground wire to the frame is not going to help anything. AC will trip the circuit breakers and fuses will blow on the DC side. There is not enough AC current available anywhere that warrants a 4/0 cable. Yes, DC does, but you will not be killed with 12V. It could catch fire, but isn't that was fuses are for?
    Last edited by Butcher; 10-24-2022 at 11:33 AM.

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    Solar and DC wiring

    Thank You both for clarifying.

    I was speaking specifically about the separate case ground on the inverter housing itself only.

    I am running 4/0 on the dc side of the inverter to the pos and neg bus bars and4/0 from the batteries to the bus bars. I am also just going to re-route my battery cables from the front of the rig to my closet to those bus bars, which I think is 6 gauge that goes to the dc loads.

    So the consensus is I don’t need to run a chassis ground to the inverter case?

    Bill
    2019 GMC 3500 SRW Sierra Denali Duramax
    2020 Reflection 315RLTS

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    I posted the installation instructions and from my understanding, the case ground is for AC protection. Nothing to do with the DC side of things.

    Lots of opinions on what people do and why they do it. Victrons are used not just for RV's and unless you have a grounding rod into the earth, I see no purpose. Of course, that is just one man's point of view. A man that is not an electrician or even a wanna be technician.

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    Solar and DC wiring

    Well took some time today and pulled the front panel from the pass through and routed the 10awg that was installed at the factory and roughed in next to the batteries. Rerouted to the passenger side of the pass through and now just need to make it pretty to pop into front closet.

    Click image for larger version. 

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    Bill
    Last edited by Redapple63; 11-26-2022 at 05:48 PM.
    2019 GMC 3500 SRW Sierra Denali Duramax
    2020 Reflection 315RLTS

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