Choosing the wrong type of wire in a mobile, marine, or off-grid electrical system can have catastrophic results.
Learning the difference between various types of wires is exactly what I’m going to teach you in lesson #1 of this Wire Basics chapter.
Can off-grid electrical systems be wired with Home Improvement Store Wire?
If you are brand new to off-grid electrical systems, you may be tempted to go to Home Depot, Lowes, or Ace Hardware and get your wiring there, but here’s why that’s a mistake: Those stores are stocked with HOME improvement products, which means that they don’t carry the best wire sizes and types for a successful DC-based low-voltage off-grid electrical system, much less the proper wires for an installation subject to the vibrations of a mobile installation like an RV or boat.
If you are building an off-grid cabin, you can most definitely use those home improvement stores for the standard 120/240v wiring throughout the cabin coming from the breaker box but stick with me, and I’ll teach you about better alternatives for the rest of the system.
How does wire insulation affect wire choice?
6 gauge THHN wire from your home improvement store has a maximum amp rating of 75 amps. The 6 AWG battery wire we sell in our store has a maximum amp rating of 120 amps. But why?
Different types of wire have different types of insulation, and the different types of insulation sometimes allow for higher amp ratings due to the heat they can withstand.
THHN wire has 75 degree celsius insulation while our battery wire has 105 degree celsius insulation. This means that the higher rated insulation can get a bit hotter on the inside before it starts breaking down, which means it can safely carry a few more amps.
This is why you see in some of our wiring kits, 6ga wire protected with a 100A fuse.
Although the temperature ratings of wire is the most important consideration, various insulations have other properties that make them more appropriate than others for various use cases, for example:
The solar wire we use has a special UV-resistant coating since it will be exposed to sunlight.
Some wires have insulated wire that is rated for direct burial underground.
Speaker wire, in general, isn’t actually rated to carry amps. Instead, from what I’ve found, it is based largely on the ohms of the speaker and shouldn’t be used to wire off-grid electrical components together.
In fact, I’ve stumbled across 4/0 speaker wire on amazon which claims to be for 700 amps, which is nearly double what is allowed per the American Boat and Yacht council. So yeah; I’m just weary of speaker wire for non-speaker applications.
Maybe you can push 700 amps with 4/0 wire in a high-powered speaker, subwoofer, or amplifier ‘car audio’ type of system, I don’t know. That’s not my realm. But 700A for things like inverters, solar charge controllers, and such for off-grid power applications would be way too much for 4/0 wire.
How do Voltage Ratings work in wire?
In general, Wire is rated for its intended purpose. For example, the SGR battery wire we use in our Battery Bank Wiring Kits includes wire that is rated for up to 600V. Since battery banks rarely. Never? exceed 600V, it makes sense that the manufacturer of battery wire would choose the proper rating for it’s intended purpose.
Our Solar wire is rated for 1000 volts, which makes sense because we have solar charge controllers rated to handle up to 250V in our store, Victron makes charge controllers rated up to 450V, Morningstar makes them with ratings up to 600V; so it makes sense why solar wire is rated for such a high voltage rating.
The voltage rating of each wire can always be found stamped right onto the wire itself and is a ‘maximum’ voltage rating; so if you had some 12V puck lights you needed to hook up, as long as the voltage rating of the wire is larger than 12, you are good to go as far as the voltage is concerned.
What’s the difference between Solid and Stranded Wire?
In a house, there is ‘Romex’ wiring running throughout the walls. Romex is a bundle of three or more wires in an outer sheath and in sizes 10ga and smaller, these are solid wires. Just one solid piece of copper.
Stranded wires serve a similar purpose, but instead of one solid wire, the ‘wire’ is made up of a bunch of much smaller wires.
What are the Pros and cons of Solid vs Stranded Wire?
Solid wire is less expensive than Stranded wire.
Stranded wire, being made up of bundles of much smaller wires, is significantly more flexible than solid wire; meaning it is much easier to work with.
Stranded wire is also not as prone to work hardening and breaking like solid core wire is.
When solid core wire is subjected to repeated bending, movement, and vibrations; over time it will wear out and break. When it breaks, the insulation will slightly hold it together and the ‘break’ will cause a mass amount of resistance and heat, which could potentially start a fire.
In a house or stationary application, this is not really a consideration because houses are not subject to regular movement or vibrations like boats or RVs are.
This risk is so great that the American Boat and Yacht Council specifically forbids solid core wire in marine applications.
So why do we still see solid core wire in use in off-the-lot RV’s? Well since Romex is the cheapest option, RV manufacturers are incentivized to keep things as cheap as possible. And when a wire bends, breaks, and catches on fire, the occupant can hopefully just step outside; step away, and call their insurance agent.
This is not something that can happen in marine applications because stepping off the side of the boat to avoid a fire introduces a whole new set of hazards, one of which could be sharks.
So if you want to build your mobile or marine off grid electrical system to have the least chance of catching on fire; opt for stranded wire in 100% of use cases.
If you are building an off grid cabin that isn’t subject to the vibrations of the sea or the road… solid core wire like romex for all of the small branch circuits leaving the breaker box is just fine.
For all of larger wire on the DC side of the system; that should still be stranded wire for the sake of workability:
The last consideration of solid vs stranded wire is workability. With small 12 AWG stranded wire vs small 12 AWG solid wire; there is a pretty obvious difference in how easy the wire is to work with and make it go where we need to, but not all stranded wire is the same. Let’s talk about strand counts.
Why are strand counts of a wire important?
The number of strands found in a wire is important for wire flexibility, especially as the wire size gets larger.
‘This’ is a 4/0 wire, which is the largest wire we have available in our store. And even as big as it is, it is still quite flexible.
Next time you are at your local home improvement store; head over to the wire aisle and grab a piece of 4/0 Stranded wire that only has 5-10 strands in it and let me know how hard it is to bend. Spoiler alert: It’s pretty much like a piece of rebar.
This same concept can be seen in the 6 AWG battery wire we sell in our store vs the 6 AWG THHN wire I picked up from ACE Hardware.
Notice how many strands of wire are in each. There are about 19 strands of wire in this THHN and 266 strands in our 6 AWG battery wire here.
What is the difference between copper and aluminum wire?
Aluminum wire used to be widely common, but has since been replaced with copper starting back in the 1970s.
Aluminum was used because although it can only carry about 60% of the amps as copper for the same physical dimension; aluminum is also generally about 30% of the cost of copper, historically; so it usually was cheaper even though wires had to be bigger.
For this reason, you’ll still see aluminum wiring in big wires with long runs from a powerline transformer to a house, for example, but for pretty much everything else, copper is the standard nowadays.
There are all kinds of problems with aluminum wiring that we aren’t going to get into since it’s no longer common, but the “Aluminum Building Wiring” wikipedia page has all kinds of info on that if you’re interested.
What is Tinned wire?
I’ve seen a lot of people post about high-quality marine wire and say that it is aluminum wire, and that’s simply not true. Tinned copper wire and aluminum wire, although they are roughly the same color, are not at all the same.
Tinned copper wire is simply copper wire that has a very thin coating of tin on each strand. Tin is more corrosion-resistant than copper, so in areas where corrosion is a hazard like on a boat in the salty ocean, tinned copper wire can help slow corrosion because of salt in the air but doesn’t affect its electrical properties.
In most of the wiring kits in our shop, as of making this article – June 5th of 2024 – we sell un-tinned copper wire; and here’s why:
With our historical focus in RV’s and vans, there is really no need for the added expense of tinned copper in a land-based application. In most vehicles, all of the factory wiring is un-tinned, and we don’t feel that it’s worth passing an additional expense on to our customers for little to no added benefit.
But… with our recent rebranding to include Marine applications here on this channel; we do plan on adding tinned versions of our wiring kits to our store in 2025 when we move to a bigger warehouse for those of you looking for sea-worthy electrical systems. So stay tuned.
What are the different safety certifications of wire?
Every wire should have some kind of safety certification, either stamped directly onto it or included on the manufacturer’s product page.
If it doesn’t have any SAE, UL, AE, RoHS, ASTM, ISO, or ID10-T ratings, it should probably not be used.
Safety ratings and certifications are a pretty deep rabbit hole because, in addition to simply having the rating or certification, having the proper rating for the intended use is equally as important.
I asked Steph to pull some of the certifications and ratings that some of the various wires in our store have and in about 3 minutes, she had these put together before I told her I didn’t need any more.
So, make sure that your wire has certifications and safety ratings.
Then make sure those certifications and ratings are appropriate for your intended purpose.
Or just buy your wiring kits from shop.explorist.life where we’ve already done the leg work for you. 😉
Conclusion
Now you should have a good idea of the different types of wires used in a mobile, marine, or off-grid electrical system.
We are going to be referring back to this article throughout the rest of this academy as we talk about how to wire various components, so be sure to bookmark it for future reference and come back to it if you need a refresher.
Before we move on to the next lesson, let me know the biggest wiring mistake you’ve made down in the comments section below so we can learn from each others mistakes.
In the next lesson, I’m going to teach you everything you need to know about wire sizes and gauges,so click up here to watch and I’ll see you over there.
