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Old 10-16-2020, 03:18 PM   #1
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Question My wiring diagram! How'd I do?

Hey guys, I just finished up my first version of my wiring diagram. I was wondering if I could get some feedback before purchasing some things. Let me know what you think!

Some concerns I'm unsure of:
1. Can the MPPT, bus bars and inverter all be connected to the same terminals on the battery? Is there an issue with charging the batteries and using them simultaneously?
2. Did I ground correctly?
3. Is it a good idea to have a fuse between the MPPT and battery? I'm concerned if it blows, then MPPT might ruin since there's will be no battery attached.

Please let me know how I did, I'm hoping to start this here soon! Thanks guys
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Old 10-17-2020, 12:33 AM   #2
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Originally Posted by bradryannelson View Post
1. Can the MPPT, bus bars and inverter all be connected to the same terminals on the battery? Is there an issue with charging the batteries and using them simultaneously?

Electrically Yes, but it would be best to make all or most of these connections off the battery (at the busbars) and just have one or two connections to the actual terminals. This isn't strictly necessary, more of a best practice (minimizing connections at the battery terminals, and also a bit tidier, there are other marginal benefits).



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2. Did I ground correctly?

Grounding can be complicated, but in this case it looks fairly straightforward. Consult your inverter documentation, the inverter chassis is probably supposed to be grounded to the negative busbar or the vehicle-chassis ground point.



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3. Is it a good idea to have a fuse between the MPPT and battery? I'm concerned if it blows, then MPPT might ruin since there's will be no battery attached.

From what I understand, this was more of a theoretical potential problem than a real issue, but your charge controller documentation would take precedence over my general understanding (which I know to be true of Victron, and I believe to be true of Epever, but not sure about others). Many controller manufacturers recommend a fuse or breaker.


I will look closer at the diagram in a bit. One thing that jumps out at me is some of your wiring is undersized relative to the fuse size (can also be thought of in reverse) which is not safe. In order to know if your wire is properly sized its necessary to know what insulation temperature rating the wire is.
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Old 10-17-2020, 02:05 PM   #3
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Originally Posted by dzl_ View Post
Electrically Yes, but it would be best to make all or most of these connections off the battery (at the busbars) and just have one or two connections to the actual terminals. This isn't strictly necessary, more of a best practice (minimizing connections at the battery terminals, and also a bit tidier, there are other marginal benefits).






Grounding can be complicated, but in this case it looks fairly straightforward. Consult your inverter documentation, the inverter chassis is probably supposed to be grounded to the negative busbar or the vehicle-chassis ground point.






From what I understand, this was more of a theoretical potential problem than a real issue, but your charge controller documentation would take precedence over my general understanding (which I know to be true of Victron, and I believe to be true of Epever, but not sure about others). Many controller manufacturers recommend a fuse or breaker.


I will look closer at the diagram in a bit. One thing that jumps out at me is some of your wiring is undersized relative to the fuse size (can also be thought of in reverse) which is not safe. In order to know if your wire is properly sized its necessary to know what insulation temperature rating the wire is.
Multi-quote doesn't seem to work for me so I'm just gonna reply.

Originally, I opted against using the bus bars for all my connections because they are limited to 250A and I wanted to accommodate a worst-case scenario of a maxed out 12v system and maxed out 120v system. I realize now that's unrealistic lol. I'll move everything to the bus bars.

Based on some people feedback from reddit, it looks like I'll be grounding the negative bus bar. Good suggestion as well.

I'll have to do more digging to see what my documentation says but it seems like everyone puts a fuse anyways... hmm.

Also, I used this chart to pick my wire gauges. Are you referring to the size from the batteries to the bus bars? Now that my design changed a bit, I'm thinking I'll use 4/0 AWG.

Thanks for all the feedback, this has been super helpful!!
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Old 10-18-2020, 02:11 AM   #4
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Another quick note: In your diagram you show you will use 6V 225aH batteries as a 12V 550aH bank. That should be a 12V 450aH bank.
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Old 10-18-2020, 01:54 PM   #5
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Originally, I was trying to accommodate a worst-case scenario where the inverter was maxed out (4000W ~333A) and all my DC electronics on (119.5A). Those together would've been bigger than the 250A rating of a bus bar. Now I realize that scenario is extremely not probable lol. I'll use the bus bars.

I'll also take a look at the inverter documentation. But as of now, with your help and the help of others, I'll ground the negative bus bar.

Thanks for your reply! Its been helpful
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Old 10-18-2020, 01:55 PM   #6
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Talking Oops

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Another quick note: In your diagram you show you will use 6V 225aH batteries as a 12V 550aH bank. That should be a 12V 450aH bank.
Lol classic. Noted, thank you
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Old 10-18-2020, 05:02 PM   #7
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Originally Posted by bradryannelson View Post
Originally, I was trying to accommodate a worst-case scenario where the inverter was maxed out (4000W ~333A) and all my DC electronics on (119.5A). Those together would've been bigger than the 250A rating of a bus bar. Now I realize that scenario is extremely not probable lol. I'll use the bus bars.
This is a reasonable consideration. I generally try to plan for worst case scenarios as well, or at least realistically plausible worst cases.

In this case you could either (1) get a higher amperage busbar (busbars are just fancy bars of copper, they can definitely exceed 250A if you find the right one (they can get pricey though unless you DIY), or (2) Connect everything other than the inverter to the busbar but have the inverter connected directly to the busbar.


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I'll also take a look at the inverter documentation. But as of now, with your help and the help of others, I'll ground the negative bus bar.
If this is in response to my recommendation to consult the inverter documentation re: grounding guidance, bear in mind that there are two aspects of grounding here, 'system grounding' and 'equipment grounding'.

System ground (in this context) = the point at which DC negative and 'ground' (in this case the "chassis-ground" connection).

Equipment grounding = connecting the (not normally energized) metal chassis' of electrical components to a common point, usually the negative busbar and/or a dedicated grounding busbar that is tied to the negative battery terminal and chassis-ground

Below is an image from Victron depicting a somewhat typical, simple, off-grid system, which shows both the equipment and system grounding connections (teal and pink text/lines are mine, everything else is original schematic):


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Old 10-23-2020, 07:17 PM   #8
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Took me a while to get around to reviewing the schematic. A couple things that jump out at me:


Green: Your Inverter Documentation Most likely requires or suggest that the designated grounding lug be connected to DC negative and/or the Chassis Ground point. (Green is just an example of what may be the recommended grounding method)


Yellow: I think you are cutting it kinda close using 6 AWG for 100A fuse blocks with 100A breakers. Depending on several factors (ambient temp, insulation rating of the wire, if conduit is used) 6 AWG can handle just above or just below 100A. If it were me I would either bump it up to 4 AWG, or use smaller 80A breakers.


Red: You cannot use a 250A fuse with 6 AWG (well you can but it won't provide protection) and you cannot use 6 AWG for a circuit expected to carry up to 120A.


If you are sure 120A is the max for the DC main circuit, you could use a 150A or 200A fuse but you want to use larger gauge wire, at least 90*C 2 AWG with a 150A fuse, maybe 90*C 1/0 AWG with a 200A fuse.


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Old 10-23-2020, 07:33 PM   #9
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One more thing I just noticed, the fuse between the charge controller and PV panels is unnecessary.


HOWEVER


You don't detail what your array looks like, but based on the numbers I suspect it is at least 3 panels in parallel. If this is the case, it is likely you need to fuse each parallel panel individually. This is only the case when three or more panels are put in parallel.


If you have an even number of panels it is also worth considering putting panels in series pairs, and then putting the pairs in parallel. MPPT controllers do a bit better with some amount of positive voltage difference between PV array and Battery.




Also, could you explain how the Dual Switch is being utilized. I think I understand what you are doing there, but don't want to make assumptions.
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Old 10-24-2020, 10:17 AM   #10
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Are you planning on having a battery monitor system? If so, this requires a shunt, which typically goes along the negative line right off the battery. I'm not saying I have done it the right way, but what I did was connect the positive post of my battery pack directly to a 60 amp ANL inline fuse, and then the other side of that fuse connects directly to the inverter/charger and MPPT (which then has an output for the DC load). The negative post of my battery pack is connected directly to the shunt, and the other side of the shunt is connected directly to the inverter/charger and MPPT. The shunt's positive line is powered from the ANL fuse (with a smaller automotive fuse for protection). Just something to consider.
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Old 10-28-2020, 06:21 PM   #11
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When you cross one wire with another put a little U shaped hump in the crossing wire so you can be sure which wire is which.
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Old 10-28-2020, 06:27 PM   #12
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When you cross one wire with another put a little U shaped hump in the crossing wire so you can be sure which wire is which.
Yup. Username checks out
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Old 10-28-2020, 11:22 PM   #13
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When you cross one wire with another put a little U shaped hump in the crossing wire so you can be sure which wire is which.
Another method is to put a dot on the points where they cross and connect and no dot when they only cross.
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Old 10-29-2020, 06:31 AM   #14
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Took me a while to get around to reviewing the schematic. A couple things that jump out at me:


Green: Your Inverter Documentation Most likely requires or suggest that the designated grounding lug be connected to DC negative and/or the Chassis Ground point. (Green is just an example of what may be the recommended grounding method)


Yellow: I think you are cutting it kinda close using 6 AWG for 100A fuse blocks with 100A breakers. Depending on several factors (ambient temp, insulation rating of the wire, if conduit is used) 6 AWG can handle just above or just below 100A. If it were me I would either bump it up to 4 AWG, or use smaller 80A breakers.


Red: You cannot use a 250A fuse with 6 AWG (well you can but it won't provide protection) and you cannot use 6 AWG for a circuit expected to carry up to 120A.


If you are sure 120A is the max for the DC main circuit, you could use a 150A or 200A fuse but you want to use larger gauge wire, at least 90*C 2 AWG with a 150A fuse, maybe 90*C 1/0 AWG with a 200A fuse.


Im trying to understand the drawing - on the MPTT you have input wires coming to it from the solar but also connected to the battery positive and negative. That to me looks like a loop. I think the panels should be the ONLY thing connected to the input of the MPTT and the output of the MPTT should go to the busbars, not the batteries directly. I would replace the busbars with the Victron Lynx busbars. They can take 1000 amps and are much more flexible with connections.
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Old 10-29-2020, 09:00 AM   #15
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DC Wire Size

Calculations for wiring size is different for AC than DC. AC (Alternating Current) is calculated using RMS values. DC (Direct Current) doesn't change so is a pure calculation. This site is designed to give wiring size based on DC voltage. https://www.wirebarn.com/Wire-Calculator-_ep_41.html
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Old 10-29-2020, 05:50 PM   #16
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Im trying to understand the drawing - on the MPTT you have input wires coming to it from the solar but also connected to the battery positive and negative. That to me looks like a loop.
I was pretty confused by this at first as well. My best guess as to what they are intending to do, is use a dual circuit switch to control both the battery and the MPPT charger. While it looks like they connect in the diagram, I believe that internally the two circuits remain isolated. The purpose is to control two circuits with a single mechanical switch. In this case to disconnect PV and Batteries simultaneously. The switch probably operates similar to something like this

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I think the panels should be the ONLY thing connected to the input of the MPTT and the output of the MPTT should go to the busbars, not the batteries directly.
I agree
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Old 10-30-2020, 06:17 AM   #17
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I was pretty confused by this at first as well. My best guess as to what they are intending to do, is use a dual circuit switch to control both the battery and the MPPT charger. While it looks like they connect in the diagram, I believe that internally the two circuits remain isolated. The purpose is to control two circuits with a single mechanical switch. In this case to disconnect PV and Batteries simultaneously. The switch probably operates similar to something like this


I agree
I still think its a loop and I believe the MPTT controller would realize that the input and output are shorted together and should shut off. The way the switch is connected it looks like the output from the solar can also go directly to the batteries and bypass the MPTT controller entirely. The wire size was higher for the direct connection from the master switch to the batteries so the resistance wouild be lower than the input of the MPTT so the current would flow to the batteries instead.
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Old 10-30-2020, 04:07 PM   #18
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I still think its a loop and I believe the MPTT controller would realize that the input and output are shorted together and should shut off. The way the switch is connected it looks like the output from the solar can also go directly to the batteries and bypass the MPTT controller entirely.
I get that it looks that way and that was my first impression to. But I think you are jumping to conclusions. If you look at how that switch is labeled it is labelled "dual circuit switch" which is not conclusive but gives some indication that these are isolated circuits.

Blue Sea Systems is one of the most popular manual switch manufacturers for marine/mobile systems, here is what the back of their E-series "dual circuit switch" looks like:


And from the description: "Simultaneously switches two isolated battery banks"


Now, Blue sea makes a bunch of different switches, some are isolated, some are not, so OP needs to be careful to choose the right switch (and if it were me I would just use two separate switches or breakers so batteries and PV could be disconnected separately). But it is at least possible to safely do what is pictured in the schematic with the right switch. It just looks confusing in the schematic.
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Old 10-30-2020, 05:58 PM   #19
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I get that it looks that way and that was my first impression to. But I think you are jumping to conclusions. If you look at how that switch is labeled it is labelled "dual circuit switch" which is not conclusive but gives some indication that these are isolated circuits.

Blue Sea Systems is one of the most popular manual switch manufacturers for marine/mobile systems, here is what the back of their E-series "dual circuit switch" looks like:


And from the description: "Simultaneously switches two isolated battery banks"


Now, Blue sea makes a bunch of different switches, some are isolated, some are not, so OP needs to be careful to choose the right switch (and if it were me I would just use two separate switches or breakers so batteries and PV could be disconnected separately). But it is at least possible to safely do what is pictured in the schematic with the right switch. It just looks confusing in the schematic.

Im just talking from experience with high voltage and schematics. The way its drawn and the way the switch functions you will have a loop. I would test it out before turning on the MPTT to ensure you have separation as intended.
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Old 10-30-2020, 06:30 PM   #20
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Im just talking from experience with high voltage and schematics. The way its drawn and the way the switch functions you will have a loop.
Its not a proper detailed schematic, from the way its drawn, neither you nor I can say for sure how it is wired or how the switch functions. There are switches that keep the circuits isolated, and there are switches that do not.

As to how the switch functions. If you are referring to the dual circuit switch pictured (which is just a guess based on the language used), I think you may be fundamentally misunderstanding how this type of switch functions. This is an illustration of how it is designed to function from the manufacturer:




While everything you are saying might be true at high voltages (I don't know, I have no experience there), this is a 12 VDC system and a 32V rated switch, which is very much a low voltage system. At these voltages one physical switch controlling two isolated circuits is entirely possible (and is what this particular switch was designed to do: control two isolated battery banks, or the positive and negative conductors of a single battery bank).

As stated above, I can't know if this is what OP is using, or if they have correctly wired everything because the diagram lacks detail. But what they have sketched out is possible with off the shelf components.

Quote:
I would test it out before turning on the MPTT to ensure you have separation as intended.
This is good advice. The proximinity of those terminals to one another also would make me worried about a short, it doesn't look like there is much by way of physical protection which would make me uncomfortable. As mentioned earlier, you and I are probably on the same page that separate switches would be preferable.
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