What Size Wire Do I Use To Wire My Solar Components? Does Wire Size Matter?

This is a question that in the beginning was confusing but with a little research it all makes sense now.... Most common wires for AC and DC applications are rated at 600v which means they can handle up to 600v. You can use them in 12v systems and 240v systems but the size matters. The other way wires are rated at is in gauges better seen as AWG . This AWG is the most important number you will need to know becus it will tell you how many amps that wire will hold. for example if you have a 14 awg wire regardless of the volts you are using you can only run up to 15amps in that wire.
Bigger is better it does reduce loss but if you go to big your connections become difficult to work becus of the size of components.

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[seminolerick]

Not explained more but mentioned, was auto jumper cables. They are designed for large amps (large gauge) ... for a short time... starting an engine should take only seconds. The insulation is more flexible for convenience...on the same rated conductor, the heat generated is short term. Continuous high amp circuits require insulation that is capable of handling the generated heat... so is denser, less flexible than jumpers, and of a different chemical composition. i.e. do NOT use jumper cables as hi amperage cable run, as their insulation WILL melt, causing a short circuit & eventual fire !

[samsonite]

Thank you sir for taking the time to make this video, learning is wonderful! One point to make about current and voltages, ratings and specs... Always use a wire gauge calculator, there are plenty of free online ones and charts to refer to (Google for one), to help with calculating gauge, length, conductor type, etc, based on voltage and current. Both factor in, 600v listed on the cable is only the rating for insulation, and safety.
One thing for DIY'ers to also understand, is that voltage x amps = watts... So a 1200w load at 12v is 100 amps current, and a 1200w load at 120v is 10 amps, this is why jumper cables on a car need to be very large gauge, and household runs a lot smaller. Length loss matters more as the voltage is lower, higher voltage can travel farther with less loss. That's why on solar it is better to use higher voltages like 48v for battery banks, and higher for solar panel runs, to keep costs lower on cabling, as you are able to use smaller gauge on the longer runs (due to lower amperes).
It can get very expensive to use a 12v battery bank if the inverter is not right next to it, as you may need cable that is very large. For example, I just wired an inverter in a guy's RV Trailer where the inverter is in the back, and the batteries are in the tongue by the hitch, and had to buy a 25 ft pair of 3/0 cables (didn't want to use chassis for ground), and cable cost $178... So higher voltage saves lots of money on cable costs.

[TruthLiberty]

6/3 with ground -
the extra red wire is normally used for a second power circuit so you can run 240 volt equipment
(120 volts on black + 120 volts on red )

Yes, it can also be used for a three way switch.

[danmurray]

Good video, Thanks... Couple of points. The voltage rating is for the INSULATOR, or plastic coating... it is not for the conductor (copper/aluminum (yes... there IS aluminum... but out of favor and hard to find)) ...
the current carrying capacity has to do with the cross-sectional area and metallurgical properties of the physical conductor.

Modern wiring sizing is based on cross-sectional area. Stranded cables will actually be physically a little larger than solid -- because solid has no air space between all the strands as there is only one strand.

I'm not aware of varying metallurgical formulations for electrical wire on the market today, so theoretically, stranded vs solid wire of the same gauge has the exactly the same current carrying capacity.

Voltage and power losses are based on distance, but also by cross-sectional area. Stranded wire is much easier to work with in most applications, and is my go to choice. What WILL impact losses are terminations and turns/bends. having monitored complex cable plants for years using thermal imaging, I can tell you that sharp bends are to be avoided, and crappy terminations, or terminations that are starting to corrode have caused nearly 100% of the failures and pre-failures that needed rework. The remaining miniscule percentage of cable plant fails were due entirely to conductor damage, either manufacturing inconsistency or (mostly) damage incurred during installation and/or maintenance.

Current Flows. the easiest way to think of where your losses are/can be is to think of water FLOWING through a hose. If you crimp the hose, flow is reduced. if you place a sharp bend (but not quite a crimp), flow is also reduced. In wiring, this introduces RESISTANCE, and resistance lowers voltage and available power downline. This resistance is also a natural property of the metal used (which is why there are few wiring formulations out there)

Personally, I'd prefer to have the cabling sized for at least 150-200% of maximum possible load. This reduces wiring resistance to a cost effective minimum, thus I-squared-R (power) losses, which show up as heat (and can have a runaway effect -- was going to say snowball)

[ahikernamedgq]

Thanks for explaining everything in such an easy to understand way, man.

[outbackeddie]

Good info. I'm getting ready to install some solar panels on my RV and it's nice to get confirmation that my choice of wire for the installation is correct.

[ilovebeading]

I did watch 'til the end. I am not an electrician but wanted to know more about the wire. Thanks for sharing!!!

[jeffreymeister]

Thanks for taking the time to explain. Very nice high level introduction to selecting proper wire sizes.

One note, your guidance on stranded vs solid is not accurate. Solid wire has lower voltage drop but is less flexible, can break under continuous bending and is generally more difficult to work with. Stranded is typically slightly larger in physical size, much more flexible and easier to work with but can lead to higher costs, high voltage drop, higher capability derating and can lead to loose terminals over time due to inherent vibrations of the machinery or the A/C current flowing through it.

[ChrisDIYerOklahoma]

Cool...just subbed in. I am running a DIY 4.9KW home off-grid solar power station. I use 4/0 between my 24v battery bank and 3.5KW inverter. Works great...kinda like using a garden hose to drink from a Big Gulp. The cable is actually TEMCo welding cable...with a lot of strands. Zero heating issues...tested with infrared thermometer. Great topic on wires/cables...have fun out there!

[TheDansana]

Current rating (Amps) is a function of the conductor cross section. Voltage and temperature rating is a function of the insulator.

Stranded or solid conductors of the same cross section have identical transmission properties at DC or AC frequencies - I'm referring to 60hz.

A stranded conductor will have a larger diameter than a solid conductor of the same cross section due to the voids between the strands.

Stranded conductors are generally not allowed to be installed in the walls per NEC code. Exceptions apply so consult an electrician.

Solid conductors are preferred in applications where the conductor is not subjected to frequent bending or flexing.

[leiftismo]

Thanx a lot sir, your video help me alot in understanding what wire should i use on my 12v loads running on the entire house. Currently im running thhn#14 and with a mix of speaker wire.

[martinda]

Just a bit of general information to clear up any possible confusion. The voltage rating on the insulation, is just that, it is what the jacket of the cable, be it Teflon, rubber, etc. is rated at. The cable itself is almost unlimited where voltage is concerned. Solid core wires are not going to have more loss per unit length / diameter than stranded cable. Stranded scores in high power high frequency application only. You can think of very high frequency current as wanting to leave the wire altogether and radiate. Skin effect is a phenomenon that increases (decreases depth) proportionally to frequency and only the outer edge of the conductor carries the current. Below about 150hz this is not really an issue. Silver plating is an excellent way to use a semiprecious metal to full advantage here, silver being the best conductor we have presently. Wire carrying current will heat up, the thinner the gauge the greater the resistance per unit length and the resistance to flow causes heat.
It's common sense really, what's the maximum current demand on your system? Choose the gauge of wire accordingly. If it's high voltage too, sort out your insulation as well.

[xanataph]

It's folklore that solid core cable has mores losses than stranded. The skin effect only becomes apparent at high frequencies. To the point where if you're moving lots of power around in the tens of MHz range you basically just use copper pipes as no current flows in the centre of the conductor at all. DC has a frequency of Zero Hz, therefore skin effect is not relevant.

However, what *can* often happen when solid core is used is that it can be harder to connect to. Screw terminals contact a smaller surface area, where as stranded cable tends to be nicely "squashed" into the terminal well or contact plate thus making a superior connexion.

The higher resistance connexion of the solid core can give rise to more heating making the situation even worse in a vicious cycle. The electrolysis action of DC current can also exacerbate the problem. This is likely where it's bad rep comes from. The solution is simple - make a good connexion. Solder a tail on or a lug etc

The problem with cable ratings is that they are essentially safety ratings. And with these cables often used on high voltage circuits a certain voltage drop can be tolerated that's no good on low voltage DC systems.

If you want to size cables generously, but not go into over the top overkill mode, *Current Density* is a good way to work it out. 1mm^2 cross sectional area per 3 amps is a good rule of thumb for 12VDC circuits. Of course all you Yanks will have to consult your tables to convert that into AWG! lol

[donf]

Semi truck battery/starter wire is 4/0 and has very fine strands. And, since semi's have multiple batteries, you can purchase inter-connect cables for wiring batteries together pre-made. Great for heavy solar wiring!

[theartisticdrive]

That was great, very to the point and informative!

[ChileExpatFamily]

Very helpful and I thank you from Chile. Jim

[infotrex]

Solid wire has less resistance than stranded and thus less voltage drop as distance increases - believe you got this backward. Do not forget about code requirement of increasing amperage requirements for continuous loads by 125%. Current (amps) on hot roofs in conduit have to be further corrected for temperature and corrected again if number of conductors in the conduit exceed 3 wires - Section 690

[LuckyPlays]

Holy cow. You are the first person I've seen to reasonably explain this so anyone can understand. Great job!

I looked into moving 12VDC at 10A(120W) accross 80' and found that i needed to run 4/0 cable to do it(very in-practable and expensive)

Iron rod would have been cheaper(like a car frame) to keep cost down.

Ended up installing a 500W grid tie inverter, and charging the remote battery bank.

[fookschool]

6/3 is for 240v split phase usage...2 hots, one neutral, and ground