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First time build, which wire size and breakers/fuses for my system? (schematic attached)

TennesseeSolar

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I now have all the major parts for my solar system and have started to assemble them. Parts are (4) 345 W panels in parallel, 60 Amp Mppt charge controller, 5.2kW 24V Tesla Battery, and 3000W 24 V inverter. Below is a picture of my 4 solar panels already mounted on a frame. I will be putting all my electronics in an outdoor enclosure which will have powered fans for air circulation. What I am not clear on though is the wire size I should use for all these components and the breaker or fuse sizes I should use. I thought about using breakers so I can turn the individual pieces off if needed for service. The one I am most concerned about is the 60 amp breaker from the batter to inverter. Looking on here this might be too small or might even need to be changed to a class T fuse?? Can you please look at this diagram and see what I might be doing wrong. Also attached are the specs. I found online for a Tesla model S battery that I am using if that helps.

Solar Cabinet 4-14-22.jpg
IMG_3816.PNGIMG_3817.PNG
 
Why are you putting 4 panels in parallel? Do you expect a lot of shading issues? With 4 panels in parallel you need to fuse each panel, typically done in a combiner box. A 2S2P or maybe even a 4S arrangement would likely be better than the 4P arrangement.

Post the full specs of the solar panels, the coldest temperature you will ever possibly encounter where you live, and details about the charge controller including the max PV input voltage and any mention of a max input amperage, if any. Also state the wire length needed to go from the solar panels to the charge controller.

A 24V 3000W inverter can pull up to 3000W / 24V / 85% efficiency = 150A. This means you need at least 1AWG wire (0AWG would be better) and a 200A breaker. The 60A breaker and 4AWG wire are vastly too small for the inverter.

Your 60A MPPT SCC should have a 75A fuse or breaker. 60A is too small since the SCC can put out 60A. 6AWG wire should be fine.
 
Rmaddy hit everything I was going to say about wire and breakers.

We really need the full specs on those panels.

My guess is they are about 10amps each - if so, 10ga wire is too small and the 30a breaker to turn the sun off - will be always tripping on you.

If you change to 2s2p both 10ga wire and 30a breaker will be fine. The mppt will probably be fine with that too, BUT, we need exact specs to really know.

“Probably” has caused lots of equipment damage!!!

Also, check carefully the low voltage cutoff on the inverter with how low you should run that battery. That is a CRITICAL piece. Because someday you will leave something on- make sure that doesn’t cause a ruined battery.

Also, you should have a shunt based battery monitor. You need to know if the battery is full, or almost empty. (I like Victron Smartshunt- but there are others too).

Good luck!
 
rmaddy and Rocketman, thank you for your quick replies. Since this is my first build I really have a huge learning curve to overcome.

rmaddy, from your questions, I really don't know if I should put the panels in series or a 2s2p configuration, but I do have shading issues. The panels will only be in the full sun about 5 to 6 hours a day, then some shade will be on them. We live in mid TN so the coldest it gets is about 0-10 F and that is not for very long at all. I am attaching the panel label for you to see. These are used panels and it appears used to have a micro-converter to make the output AC. That has been removed before I got them and now they just have the DC wires coming out of them. When I measure them with a volt meter I get about 56V DC on each.

The outdoor enclosure box I am putting everything in will be right below the solar panel array so the wire length from panels to controller will be about 10 ft.

In reading for hours last night on here I agree with you about the 0 AWG wire and 200 A breaker or fuse. I think from reading here I should go with a class T 200 A fuse?

I will also change the MPPT to battery breaker/fuse to a 75 A size.

Rocketman, to your questions, I attached the specs. for the MPPT and inverter. From the inverter specs. I think its saying the low voltage cutoff is 20 V?

I will also look at getting a shunt based monitor.

For both of you is the class T 200 A fuse above the correct piece I need? Also for the 75 A fuse or breaker do you have a recommendation as to a brand or type that is good (and not cost a fortune)?

I am building this as primarily a backup electric source so I don't plan on running it every day. I would just occasionally turn it on to make sure its still working.

Based on your comments I redid my schematic and attached it as well.

Solar Cabinet Revised 4-15-22.jpg

MPPT Specs:
IMG_3820.jpg IMG_3821.jpg IMG_3822.jpg
IMG_3823.jpg

Inverter Specs.:
IMG_3824.jpg

Solar Panel: Its talks about AC output but the micro-converters on the panels were already removed, so these are just DC now.
IMG_E3819.jpg

Thanks for all your help! Trust me this has gotten me farther along already.
 

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Don't cheap out on fuses/breakers. Quality versions cost a little more but they are cheaper than fires. Look for Bussman or Blue Sea brand breakers. Littlefuse brand fuses are high quality. Avoid cheap no name Chinese knockoffs.

Here's an example Blue Sea breaker (I used one of these for my charge controller):


I am not familiar with the needs of the Tesla batteries so I can't say whether you need a Class T or other type. I just know it should be 200A. Hopefully someone else can help with the type of fuse needed for the battery.

It's going to be difficult to give good advice on the panels and charge controller since those panels don't show the basic DC specs you normally see.
 
rmaddy, thanks for the breaker advice. I think looking on here the Blue Sea are looking good to me.

DerpsyDoodler, the spec. sheet you found for the panel looks like almost the same as mine, except mine has something about 20 A max overcurrent protection and on the sheet you linked it says 15 A max. series fuse.

I am now a little confused on how to wire the panels though. I called the guy I bought the panels from tonight. He brought up a good point that I dont want to wire these in series because I am measuring 56 V from one panel, making 2 in series will push this even higher to 112V. The converter has to then take this back down to ~24V for my battery, so staying with the panels in parallel is closer to this. His suggestion was the sketch below. What do you think about this?


Solar Panel Wiring 4-15-22.jpg
 
I called the guy I bought the panels from tonight. He brought up a good point that I dont want to wire these in series because I am measuring 56 V from one panel, making 2 in series will push this even higher to 112V. The converter has to then take this back down to ~24V for my battery, so staying with the panels in parallel is closer to this.
I have 3 330W panels in series on my 24V system. That's about 120V. There's nothing wrong with that. It actually has the advantage of allowing the charge controller to provide charging power to the battery in lower light conditions.

However, you must make sure your charge controller can handle the voltage. Oddly I don't see the normal "max PV input voltage" specification listed for your charge controller. That's the most important spec so you don't fry the controller. Though the "working voltage" is listed as up to 150V. So you should be able to put the panels in a 2S2P arrangement.
 
rmaddy, thanks for the breaker advice. I think looking on here the Blue Sea are looking good to me.

DerpsyDoodler, the spec. sheet you found for the panel looks like almost the same as mine, except mine has something about 20 A max overcurrent protection and on the sheet you linked it says 15 A max. series fuse.

That difference is probably related to fusing the microinverter's AC output as opposed to the DC. Since you don't have the microonverters, I would go with the DC specs. This means you will fuse or breaker the panels at 15A.

I am now a little confused on how to wire the panels though. I called the guy I bought the panels from tonight. He brought up a good point that I dont want to wire these in series because I am measuring 56 V from one panel, making 2 in series will push this even higher to 112V. The converter has to then take this back down to ~24V for my battery, so staying with the panels in parallel is closer to this. His suggestion was the sketch below. What do you think about this?


View attachment 91441

The higher voltage is better. Like RMaddy said, better for charging in low light conditions as well as it means thinner wire and less voltage drop on the wire.

That said, dealing with high voltage is dangerous. Use caution while wiring and don't do anything until you have a plan.

What's the actual brand and model of the mppt
controller?
 
What's the actual brand and model of the mppt
controller?
The charge controller I have is this one:

1650119036741.png

What about the comment though about inputting higher voltage and then having to step it down to 24V? Maybe I am not thinking about that right, but does that matter?
 
With an MPPT controller, youre better off using a higher voltage and letting the charger do what it does. If you were using a PWM controller, that would be a different story.
 
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