January 5, 2020

Solar Project: Figuring Out the Wiring

In my last solar project update, I showed you the battery box Dan came up with. The batteries and charge controller are now installed in the box, so the next step will be connecting all the components together.

For that, we need various sizes of cables and circuit breakers.

To understand how it all fits together, I drew a diagram.

You should be able to click to biggify.

Cable size is based on current (amperage), so they become progressively larger as the electricity travels from source to use.

I used the sizes recommended by Prepper's Total Grid Failure Handbook and the charge controller user manual.
  • 10 AWG from solar panels to charge controller
  • 2 AWG from charge controller to battery bank
  • 4 AWG golf cart battery interconnect cables between batteries
  • 1/0 AWG from the battery bank to the inverter

The manuals helped me size the circuit breakers too.

Solar is a direct current (DC) system, so all of these are DC circuit breakers. Household (AC) circuit breakers are not recommended.
  • 30 amp (12-72 volts) between solar panels and charge controller. The formula is the PV array's short-circuit current (LSC) multiplied by 1.56. The LSC is listed on the back of the panels. For us, that was 6.39 x 3 panels = 19.17 x 1.56 = 29.9 or 30 amps.
  • 60 amp circuit breaker between the charge controller and battery bank was recommended in the charge controller manufacturer.
  • 175 amp circuit breaker between batteries and inverter was recommended in the inverter manual.
They are marine breakers, so they are waterproof. Even though they will be installed in the battery box, that still seemed like a good idea.

All of that is probably more technical than you're interested in, but I want to have all the information where I can find it. That's in case we need it for future reference. A blog comes in handy for things like that!

The next step will be grounding the system.


Gorges Smythe said...

Sounds too complicated for my failing mind!

Leigh said...

Gorges, that's why I had to write it all down in a place where I wouldn't lose track of it!

Cockeyed Jo said...

Very wise to write it down.

Boud said...

I like reading about technicalities like this. And I hope we get to read about every stage all the way to LIGHTS! CAMERA!ACTION!

Boud said...

Also, next book? What was your last book? Potential readers need to know. That would be me.

wyomingheart said...

Wow! What a lot of information! I am going to purchase that book and study, for sure! I am so excited for you and Dan to get this project completed, as I know y’all probably are too, lol ! Have a great week!

Goatldi said...

Good job. Throughly researched as is your manner. Research prior to project eliminates pulling out ones hair when doing it mid project.

Your post reminded me of the very first home we looked at in Mendocino county. It was a ten acre homestead originally built in the the 1970s during the back to the land movement.

When we found it almost 40 years later the two main points that kept us from purchasing the property were the lack of any outbuildings for the stock we were bringing and the really funky solar system. Basically multiple huge batteries with lots of exposed wiring. We politely declined.

If the time comes to sell your place people will be standing in line for a chance.

Rain said...

Leigh this is priceless information for everyone. I think it's a great idea to blog all the technical details for sure. One of these days I'll be looking at your blueprint and understanding what I need to do. I'm very visual so your blog posts about this installation are a godsend to me! Thank you!

Leigh said...

Jo, and better written down than on scraps of paper! (my usual method).

Boud, thank you! I was hoping someone would appreciate this!

The book would be the sequel to 5 Acres & A Dream The Book. I continue to receive encouragement from people about that book, and so much has changed since it was published that I felt it needed an update. In between then and now I've also published Critter Tales,, How To Bake Without Baking Powder,, and Prepper's Livestock Handbook. They are all listed here.

Wyomingheart, definitely get that book! It is the best I've found on the subject. Easy reading and very helpful.

Goatldi, I'm sure a lot has changed and improved for solar installation since then! Thankfully! So much of it is put together for you now, like the connectors on the panels and wiring. Resources too. Finding a book by someone who had put in their own learning time and knew what they were talking about was important, especially for this!

We're not really planning to sell, but I know better than to say never. That being said, our whole system is set up so that it could be taken with us if we wanted to. :)

Rain, thanks! I found a lot of information on the big components. Everybody talks about sizing panels and batteries, and the kind of charge controllers and inverters to get. But it was harder to find specifics about wiring, circuit breakers, and grounding (the topic of my next post. :) I hope this post proves helpful to others.

Debby Riddle said...

This is very helpful especially with all the planned power outages in CA.

Leigh said...

Debby, fortunately, we don't have planned power outages, but if we did this would be essential, because this will power at least my freezer and hopefully a refrigerator. It would be more difficult to preserve and keep food without them.

Ed said...

When I do any sort of major electrical project, I have to draw a diagram and think on it a bit before starting. Electricity never came easy to me and isn't what I would consider in my wheel house especially beyond basic household wiring.

Lady Locust said...

Awesome - also, love your word "biggify." :-)

Leigh said...

Ed, it's the same for us, although this has forced us to stretch our understanding a bit. Understanding voltage and amperage didn't seem to be as necessary for household wiring because the system is already set up. There are more options with solar components so it's meant more study. That's one of the reasons it's been slow going. Well, that and the weather!

Lady Locust, it's exciting to be getting closer!

squire said...
This comment has been removed by the author.
squire said...

Lead acid batteries cause corrosion from out-gassing. Please house components close but not in the same compartment.

Mike Yukon said...

Diagrams and drawings, even crude ones will save you money and time by not having to re-do even a simple project.

Leigh said...

Squire, I'll look into that, thanks.

Mike, that is so true. I've also discovered that drawings and diagrams are a wonderful communication tool. Dan and I usually picture different things in our minds when we discuss an idea. Drawing it out really helps with that.

Powell River Books said...

We depended on our good friend John to figure out the wiring necessary for our solar system. When he redid our cabin deck this winter he had to move the battery storage box. It was to heavy to move so he had to disassemble all the batteries and move them one at a time. But we now have a nice new cedar deck that should last us at least another 20 years. - Margy

Leigh said...

Margy, you must have some heavy-duty batteries! But that's how they usually are. You must be thrilled with your new deck.