Help reviewing my wiring diagram - design, cable sizes & fuse choices

DIY
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As the subject says, I would greatly appreciate if someone drops an eye over the diagram I’ve been working for the past couple of weeks. The diagram is divided in several charge source & loads sections: solar, b2b, shore & ac, 12V fuse box.
I’m not in any way experienced, the diagram is the result of a long research, manuals & data sheets interpretations, but that’s just reading and self assuming, hence I’d kindly ask a sharp eye to check whether my cable sizes, fuse choices, ac load distribution etc is correct or at least in a good ballpark - and of course, whether I’m missing something, if I should change something, new parts I should consider etc.

wire-diagram-multiplus
wire-diagram-multiplus5670×4800 1.67 MB

should you have any quwestions, or any issues with the diagram (.png) do let me know

looking forward to your feedback

Adrian :handshake:

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Hi Adrian,

I will start from the upper left corner…

You should not connect the two different types of modules in parallel. They have completely different voltages, this will not work, you could even damage the low voltage modules. Install a second MPPT for the diffenet type of module instead.

Then I would not recommend this inline MC4 diodes. Even if they say they can handle 15A, there are test out there in the internet showing them burning at lower currents already. If you use separate MPPTs, and do not parallel this different modules, you don’t need this diodes at all.

The circuit breaker is to “strong”. In this case it will not cause any problem (as the input current is limited through the pv modules), but usually it should be selected as strong as the current capacity of the used cables. In your case 6mm² can handle ~31A, so a 25A breaker would be fine.

Regarding the MPPT, - as mentioned before, you should use different MPPTs for different PV arrays with different voltages.

Then regarding this 60A breaker/fuse (the type with M8 screw) - for me this type is not too trustable. And why are you mixing this breakers with the Victron breakers + fuses? Why don’t you use always the same type? A fuse holder is more flexible, a defective fuse is easy to change, this M8 breaker isn’t… And you can adapt the fuse capacits if needed in future.

Fot the MPPT(s) a circuit breaker like the one in the PV input would be fine. In general, you have a lot of breakers in there… :wink: but yes, makes service much easier then.

Did not check the AC Load part yet…

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Hi Jetlag, and thank you for taking the time to begin go over the diagram!

  1. so the panels in branch 1 are connected in series thus making both panels vmp (18.6V*2) 37.2V , even so it’s not safe to connect in parallel a second branch with one foldable panel that will be at the same voltage as the first branch? so around 36-40V?

  2. in the other case if a second MPPT is required, can I downsize the one I have (100/50) to 100/20 for example? would that be enough for the series connected branch 1 2x130W? and to buy a second one when needed, same size or whatever the foldable panel might be at that point…

  3. The circuit breaker is to “strong”. In this case it will not cause any problem (as the input current is limited through the pv modules), but usually it should be selected as strong as the current capacity of the used cables. In your case 6mm² can handle ~31A, so a 25A breaker would be fine.

    I assume you are talking about the PV DC isolator in my diagram, in case I will downsize the MPPT and leave just branch 1, and leave cables as are, I will downsize this to 25A

  4. Then regarding this 60A breaker/fuse (the type with M8 screw) - for me this type is not too trustable. And why are you mixing this breakers with the Victron breakers + fuses? Why don’t you use always the same type? A fuse holder is more flexible, a defective fuse is easy to change, this M8 breaker isn’t… And you can adapt the fuse capacits if needed in future.

    I was thinking the same in the beginning, but everywhere I searched for info, such breakers were being used, including almost all official schematics for Victron MPPT:

    image
    image1636×1494 195 KB
    this type or other type, is 60A correct here for 100/50? what about 100/20 ?

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I would recommend an Orion XS instead of the Orion TR

It is more programmable and you can regulate the charging power.

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If you use that type of breaker use a really good make such as Blue Sea from a reputable supplier. DO NOT use the cheap no name breakers bought on many websites, these have a dreadful reputation.

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Regarding 1. - In my opinion one should never parallel different type of modules. Even though the modules seem to have the same Vmp in one point, what about the temperature coefficient, or what about one is shaded, one not… Then unexpected behaviour can happen, and you might not get the power you need, or even worst - something could get broken. And if you today don’t know which foldable module you want or get in future, you are more flexible with two MPPTs.

2.Yes, you are right, you should take a smaller MPPT, the 100/20 is a good choice. Take two of them, and it should be not even a lot more expensive.

3.Yes, I mean the breaker in the PV path. I understand, that it is sometimes just used as switch und turn off the PV voltage. And this is fine, I just wanted to add the aspect with the ampacity.

4.Well, here you should either follow the hint from pwfarnell, or use fuses instead. I know, that these breakers are often displayed in the schematics, but I’m not a fan of this. I once had (>10 years ago) a problem with one of these, and it caused me a lot of trouble. It was obviously ok, but it had a bad contact or so and at higher currents there was a big voltage drop across the breaker. Also the breaking capacity, especially for LiFePO4 batteries where extreme peak currents can occur, is an important factor. So you should be clear which one you choose.

Annother aspect could be, a defective breaker is much more of a headache when you are far away from home with you van, then to just replace a fuse. Just brainstorming. :wink:

Regarding the AC distribution - looks good to me. Just a hint, there are RCDs with integrated breakers. E.g. this one ABB C16/0,03. And is the C rating ok or even required in you country? A B-characteristics is more sensitive…

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  1. okay, I’ve updated the diagram and I will take a second controller and removed the line diodes - I was anyway on the fence with this decision and just needed an extra reason on why to do one over the other
  2. for this, again, updated the diagram with new MPPTs and breakers/fuses from MPPTs to + busbar
  3. I already have two of these isolators (came in a 2 pack so I can use them now for the second MPPT) for PV path with 63A 500V max specs. Can I/is it safe to use them here anyway if I already have them, or send them back and take some 20A-32A ones instead?
  4. okay, thanks for the heads up on the circuit breakers, I will use quality ones or just go with MEGA fuses same amperage that I can keep a bunch of with me should something go sideways while on the roads.
  5. I live in Germany and found the information that RCDs type A and MCBs type C should be the way to go, but I might be wrong. Would you recommend going with something else? I guess the RCBO you suggested from amazon has the same characteristics - speaking of, if I go with with a RCBO instead of a RCD/MCB combo, will I need one on the MultiPlus input (the one with specs you suggested 16A Type C, 30mA Type A), and another one on the MultiPlus output for both the wall sockets (again, same specs as you suggested) - is this a correct assumption or I should go with other specs for one or the other?

updated wire diagram
updated wire diagram5670×4800 1.8 MB

  1. in rest, does everything else looks fine to you and with the right size? like the main LiFePO4 ANL fuse, b2b MIDI fuse, multiplus MEGA fuse, orion breaker/fuse size, the downsizing of the b2b cable right at the input of the orion?
  2. would you recommend (or is it needed) adding a gx device like cerbo or idk, to track everything, or the VictronConnect app would suffice in the beginning?

Thanks again :waving_hand:

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Witzig, da unterhalten sich zwei in englisch obwohl beide aus DE sind… but let’s keep it in englisch for the rest. :wink:

1.fine

2.fine

3.you can use them, no worries about that. as mentioned, the current from the PV modules will not exceed the limits of your 6mm² calbes.

4.fine

5.well, in Germany usually the B-characteristics is used. C is “only” for high inrush current applications like big motors or so. So in your case not really needed. In e.g. Italy or Switzerland this C-type is the standard, but I don’t know how this is handled for foreign camper vans. I don’t think someone will ever controll this.

And yes, you need one (either seperated MCB+RCD or combined RCBO) at the AC_In and one at the AC_Out of the Multiplus. 30mA is correct, the C or B type as stated above.

The MCBs you have before the outlets must be double pole, - correct!

And just saw a cable, that should be obsolete: The ground path [MultiPlus Case GR] is not needed. Both already have a connection over the chassis. These two chassis points have (or should have) a good connection anyway, so your 25mm² calbe would just be a parallel wiring. And the chassis ground of the negative busbar is also way to thick. Here a ~2,5mm² or similar is far enough. At this point no big currents are expected. Only in a failuer situation, there could be short peak, so no need for 50mm². :wink:

6.The fuse rating from the battery to the positive busbar is to high. A 50mm² cable can carry ~150A. See this table as reference. The corresponding fuse should be 125A. The same is valid for the fuse from the busbar to the Multiplus. The fuse at the Orion is fine, - DirkW recommended the Orion XS. The rest seems ok.

7.Regarding the Cerbo, - I would not add a Cerbo. You can controll all over BT with VictronConnect. The Cerbo would allow a nice visualisation (with an additional display) of course, but is not needed for the function itself. Without Wifi/Ethernet it is anyway not remote accessible. And yes, you could add a Cerbo/RasPi later on without any problems.

One more hint, - regarding the battery. How accurate is the SoC calculation in the BMS? Often we read in the forum, that batteries calculate the SoC not very good, and you have a increasing drift of the SoC. Here a SmartShunt could help to be a more accurate measrement device.

The Multiplus with 1600W could be problematic with the 50mm² cable you choosed. Depending on the lenght (you just say “short") and the duration of the power consumption in this range (there are ~130A) this could be a problem.

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  1. cool then, I will go with the 2x ABBs the ones you recommended when I’ll order. 16A Type C trip & 30mA Type A RCD on the MultiPlus AC input and another with the same specs on the AC out for my two wall sockets.
    • okay, I will consider removing the case ground cable of the MultiPlus and downsize the house battery main negative busbar from 50mm2 to something like 10mm2 or something less.
  2. in this case, should I downsize both (house bat & multiplus) fuses to 125A? or better increase the 50mm2 cable for the house bat & multiplus? what cable+fuse would you suggest in this case?

The Multiplus with 1600W could be problematic with the 50mm² cable you choosed. Depending on the lenght (you just say “short") and the duration of the power consumption in this range (there are ~130A) this could be a problem.

the cable runs for the bat to busbars & multiplus to busbars are going to be probably under 1 meter or even less, 0.5m …

  • I would consider the Orion XS, but it’s almost double the money so for now I’m doing the budget with this and I will keep it in mind.
  1. okay, I will just use it with the VictronConnect app in the beginning.

One more hint, - regarding the battery. How accurate is the SoC calculation in the BMS? Often we read in the forum, that batteries calculate the SoC not very good, and you have a increasing drift of the SoC. Here a SmartShunt could help to be a more accurate measrement device.

I honestly have no idea how accurately it measures the SOC, I can only see it in an app that I use via bluetooth, which I think sucks big time, the app I mean, so BMS might be similar in terms of quality. Regardless, I will add a SmartShunt to the diagram. Together with the above changes, I will post again the updated diagram.

Thank you again! :christmas_tree:

10

5.Regarding the RCBO, - the link I shared here was just an example that there are combined RCDs+MCBs in one package that will need less space. That’s why I linked a C16/30mA type. But afterward we talked about the B- or C-characteristics. In Germany the standard is the B-Type. C is only taken for special electrical installations. And I don’t know from any regulations, that would require a C-Type in a camper van. I would recommend a B-Typ RCBO, B16/30mA.

6.If the cables are not very long anyway, then you could change them to 70mm² with 150A fuses. This will definitly be the “premium” solution. You have then enough reserve for every 1600W application. BUT - please keep an eye on the contacts and crimps! Every good cable is worth nothing if the connections are bad.

Regarding the SoC, - the Smartshunt will be a benefit for the system.

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wire-diagram-multiplus-v3
wire-diagram-multiplus-v35670×4800 1.76 MB

  • so, I’ve updated the main house battery cables & fuses, as well the ones of the MultiPlus from 50mm2 to 70mm2 and the fuses to 150A ANL and MEGA respectively for the MultiPlus to match the new cables.
  • I’ve left the redundant ground MultiPlus case ground cable in the diagram to have it as complete as possible and will adjust this at the installation phase depending on “packaging”, placing and space.
  • I’ve changed the RCD/MCB combo with single RCBO units the 32mA type A, 16A type B we discussed about.
  • I’ve added a SmartShunt w/ Battery Monitor on the negative main house battery cable for better tracking.

If you have a couple of seconds, throw an eye on the hopefully final version of the diagram just to make sure everything looks fine and decent :blush:

Either way, I want to thank you again for your time taken to write the messages and look at the diagram, the beers are on me when you’re in Berlin or we cross paths anywhere that might be :clinking_beer_mugs:

Until then Merry Christmas and a Happy New Year to everyone!

Adrian

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Only small remarks:

Why you want to use ANL and MEGA fuses, why not only one type? Again easier to have replacement when you’re out there in the world with your van.

The Chassis ground-bars could be combined as it is anyway the same potential. The connection of the RCBO should be L1 on the left, and N on the right. But this is “Tüpflischisser” style. :smiley: This is relally important in 3-phase applications, here this is just a hint.

Apart from this, - looks good and will work very nice! Greetings from the very south of Germany! :slight_smile:

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You’re right, I changed everything to MEGA for ease of replacment and convenience.
I saw the markings on the ABB photos, but kept the order like that because it was faster :rofl: but yeah, I’ve changed now the order, L goes on the left, N goes on the right to have it all in order.
Also, I kept only one ground-bar for all load distribution box.

I will start putting things together and start ordering components :high_voltage:

Wish you all the best!
Adrian

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Hello Adrian. Very nice drawings. Can you tell me what you used to make them? I would like to do something similar. Thanks

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Hello Colin, sure, I’ve used draw.io - it’s really nice, it’s pretty intuitive overall but even so it takes a bit of time to get used to. You can find a lot of guides on their website on how to do one thing or the other.

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I have a similar question, I’m using draw.io as well , but where did you get you images from please ?

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They are actual product photos from amazon, victron official website or other shops online and had the background removed where was the case with this: https://www.remove.bg/

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Thanks Adrian