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How to Wire a Solar Disconnect for a DIY Camper Electrical System

How to Wire a Solar Disconnect for a DIY Camper Electrical System

In this blog post, I am going to teach you how to wire a solar array disconnect, why you need one, and which one to use when installing a solar array into your camper electrical system.

A solar disconnect is not only convenient, but is also a code requirement. By the end of this blog post, you will know what disconnect to use, why you need to use one, and how to size the disconnect.

DIY Camper Solar Disconnect Parts List:

Column AColumn BColumn C
This parts list contains the parts necessary to wire a dual pole solar disconnect between the solar array and charge controller of your DIY camper solar electrical system.
ProductQtyLink
Solar Disconnect Breaker1
Din Rail Breaker Box1
10 AWG Red Wire30
10 AWG Black Wire30
3/4" Truss Head Screws12
Cable Clamps4
The following parts are not 100% necessary, but make for an incredibly clean and professional installation:
Wire Duct1
10 AWG Ferrule4
1/4" Red Heat Shrink2
1/4" Black Heat Shrink2
Din Rail End Stopper Block2

Disconnect Your Solar Array

Before messing with this… It’s important to remember that if the solar panels on the roof are already wired together… there WILL be power coming down and will likely be enough to shock you.  I’ve already triple checked checked that my solar panels are disconnected from the wire coming through the roof entry gland and when YOU go to start this part of YOUR project.  I highly recommend you do the same.

Drill the Holes for the Solar Disconnect Box Wire Glands

Using a step bit and drill, I’m going to drill the holes into the din rail enclosure for the wire entry glands.

Install the Wire Glands for the Solar Disconnect Box

Since this doesn’t need to be waterproof, it’s fine for wires to share the same wire glands.  I’m doing incoming wires in one glad, and outgoing in the other.

If you were going to be installing multiple breakers into this box for, say, a system with multiple charge controller… be sure to offset the wire glands so you can fit two additional ones.

Secure the Solar Disconnect Box to the Backer Board

Using some truss head screws, I’m going to secure the enclosure to the backer board.  Four screws should do the trick.

Install your Wire Duct (Optional)

Next, I’m going to install some wire duct.  This is completely optional but makes for a super clean install.  Wire duct is simply a piece of plastic channel with the little ‘fingers’ on the sides.  It’s made to run wires through and the slots make it easy for the wires to ‘exit’ the channel to connect to the components.  It has a lid that snaps in place on top and just keeps all of your wires nice, tidy, hidden from view, and adds a nice layer of physical protection to the wire. It simply screws to the backer board with some truss head screws. This is what the final product looks like with the wire duct installed:

Install the Solar Disconnect Breaker into the Solar Disconnect Box

Next, I’m going to install my breaker onto the DIN rail.  There is a little lip on the top back of the breaker that hooks over the top of the din rail.  On the bottom, there are two little tabs that extend and retract to hold the breaker to the rail…  Push the little retainer clips down and clip the breaker onto the din rail.

Cut, Strip, & Crimp the wires for the Solar Disconnect Breaker

I’m going to take the wires that are coming from the solar array and measure them out so they can reach the top of the breaker and cut off any excess.  Next, I’m going to strip the insulation off of the end of the wire and put a ferrule and heat shrink on the end.  I covered ferrule installation in depth in this video and you can check that out for more info: https://www.youtube.com/watch?v=h8CHAVmpPFw

Connect the Incoming Wires to the Solar Disconnect Breaker

Now I’m going to insert the positive and negative wires into the top of the breaker and tighten down the terminal screws.

Cut, Strip, and Crimp the Outgoing wires for the Solar Disconnect Breaker

This is the wire that will go from the disconnect breaker to the charge controller.  This wire will be the same gauge as the wire on the other side of the disconnect, so I’m going to just use the excess I just trimmed off.  I’m going to Cut, strip, and put a ferrule and heat shrink on each one of these wires.

Connect the Outgoing Wires to the Solar Disconnect Breaker

…and then I’ll take each of those wires and put them into their respective spots in the bottom of the breaker.

Tighten the Wire Entry Glands & Reinstall Solar Disconnect Box Cover

Now I’m going to tighten up the wire entry gland…and put the cover onto the enclosure with the provided screws.

Install Cable Clamps to Hold Solar Wire in Place

Next, I’m going to take my cable clamps and put them on the incoming and outgoing wires to secure them a bit more inside of the wire duct.  This is a good idea regardless of if you are using wire duct or not.

The next step would be to connect the outgoing wires to the charge controller, but that will be covered in its own blog post and you can read more about that here: https://www.explorist.life/how-to-wire-a-solar-charge-controller-for-a-diy-camper-electrical-system/

Is a Disconnect Between the Solar Array and Charge Controller Necessary?

Short answer: Yes. And here’s why:

NEC 2020 Article 690.13 says that “Means shall be provided to disconnect the PV system from all wiring systems including power systems, energy storage systems, and utilization equipment and its associated premises wiring.

Is a Dual Pole Disconnect Necessary for a DIY Camper Solar Array?

Again, Yes… And here’s why:

NEC 2020 Article 690.13 section (E) States that “ The PV System disconnecting means shall simultaneously disconnect the PV system conductors that are not solidly grounded from all conductors of other wiring systems.

Since camper electrical systems are generally NOT grounded, this means that both the positive and negative conductors from the solar array need to be able to be simultaneously disconnected, and our dual pole breaker does exactly that where those other breakers and switches do not.

What size of Breaker is needed for a DIY Camper Solar Disconnect?

Short Answer. As long as your solar array has a short circuit amperge of less than 50A and a short circuit voltage of less than 250V… You should use a breaker at is at least 50A and at least 250V. Any higher on either of those numbers is fine.

Long Answer: Both the voltage and the amperage of the breaker just needs to be above the voltage and amperage that you EVER anticipate flowing through the breaker.

You don’t want too much voltage flowing through the breaker, as it will damage the breaker. The breaker in the parts list above has a minimum voltage rating of 250V (or 400V, depending which one is in stock). A properly designed camper solar array will never exceed this.

The amperage just needs to be high enough that it will never trip automatically. This breaker is simply being used as a disconnect and can offer NO overcurrent protection in this location.

Providing overcurrent in this location is impossible because the operating current of the array and the short circuit current of the array are nearly identical and therefore impossible to properly provide overcurrent protection for. This is perfectly fine and is well within electrical code/standards.

Again… This breaker is just acting as a switch and is offering no overcurrent protection. This is why I usually use a minimum of 50A/250V breaker even though it is on 10 AWG Wire.

FAQ’s about Camper Solar Disconnects:

Q: Can’t I just use one of the commonly used 12V DC resettable breakers/switches like this?

A: No. You shouldn’t. For two reasons…

1: Those breakers do not satisfy the “Must disconnect both the positive and negative wire” requirement set by NEC 2020 Article 690.13 section (E)

2: Those breakers have a max operating voltage of 48V, 48V, and 24V (respectively, top to bottom) and a properly designed solar array controlled by an MPPT charge controller will VERY MUCH LIKELY exceed 48V.

Installing a Dual Pole Solar Disconnect for your DIY Camper Electrical System – Conclusion

Now you know how to wire a dual pole solar disconnect, how to size your disconnect, and why a disconnect is necessary.

Thanks for reading and I hope you found this blog post helpful and if you did… It’d be awesome if you would share it with somebody, or a group, who you think could use it.  Hit the like button, and leave any questions you’ve got in the comments section below.  Subscribe if you want to see more DIY camper building tutorials and I… will see you in the next project.


Benjamin

Wednesday 24th of November 2021

Since this switch is providing no overload protection, why couldn't you just use a "Double Pole Single Throw Switch" for both the wires? Thanks!

Nate Yarbrough

Wednesday 24th of November 2021

Mainly because Double Pole Single Throw Switches rated for 250+ VDC don't really exist that I'm aware of.

Chad Chupek

Thursday 21st of October 2021

I’m about to dive into the solar setup on my 5th wheel, 2020 Grand Design 367bhs. My wife wanted to remodel the bathroom and I took the opportunity to pull the wall behind the toilet to run a roof mount antenna for my Pepwave router and install a 1-1/2” electrical conduit from the roof to the basement. I installed a 8x8 waterproof box (Lowes) with the conduit coming in from the bottom. I’d like to use a combiner box to receive the solar arrays (liking that each leg coming in will be fused and has surge protection)and output the wiring from the combiner into the box I installed to the basement where the MPPT will live. The question I have is regarding code. The roof mount combiner will have a dual pole disconnect; however, will code require one located in the bay near the charge controller? Thanks for any help you can provide on this!

Charlie B

Thursday 2nd of September 2021

Nate- As you may have mentioned in one of your videos, the dual pole breaker slides on the den rail in the box you recommend, and there are open slots on either both sides or one side due to the opening being larger than the breaker. I thought you had mentioned a way to secure the breaker in a location within the box, but I can’t seem to find it. Can you help me with this?

Norman Owens

Thursday 19th of August 2021

Very good, and logical information. And reasonable express.

Renee

Tuesday 10th of August 2021

Thanks for this post, Nate. For grounded charge sources, would there be any reason / benefit to using a din rail breaker (e.g., if I connected the van starter battery through the same breaker box then to the DC-DC charger), or would a fuse (per your wiring diagrams) be better for wire protection? Could I replace the fuse with a normal single pole breaker to act as a disconnect switch, or would you recommend adding a separate switch in addition to the fuse?

Thanks!

Nate Yarbrough

Tuesday 10th of August 2021

The way I show in my diagrams is indeed the way I recommend wiring this stuff, but feel free to play electrical arts and crafts if you feel so inclined. Just know that I don't necessarily vouch for any changes.