# Stranded or Solid (and why)



## rselectric1

I brought the EC who originally trained me into a job recently for his manpower etc. He is *now* using stranded 12 & 14 where he used to hate it. We always used solid 12 & 14 when I worked for him years ago.

I respect him but his reasoning for the switch was unclear to me. (He wasn't even really sure, they just switched over the years)

Here are my perceived pro's with stranded vs: solid (12 & 14 only)

*Solid*
Stays aligned on spools better (less "knots")
Easier to terminate on devices (no rogue strands to worry about)
Much neater service panel work 
Twisting terminations more solid (no pun intended)
Easier to push through greenfield for whips

*Stranded*
Easier to press larger devices like GFCI's and dimmers into boxes
Smoother pulls on long home runs

I'm curious what your experiences are.

EDIT-I neglected to mention that all work in my areas is required to be in conduit. We can't use romex at all. (Thanks Woodchuck)


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## 480sparky

12 and smaller, solid unless specs or manufacturer dictates otherwise.

10 and larger, stranded if at all possible.


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## woodchuck2

For me it depends on the job and what requirements are agreed upon. Anything in EMT/Conduit is stranded but most other work is solid wire. I do however like to use Ideal Pigtails for most connections as they are 12ga stranded copper with a forked connector so the connections can be pushed into the back of the box and there is less stress on the device.


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## rselectric1

woodchuck2 said:


> For me it depends on the job and what requirements are agreed upon. Anything in EMT/Conduit is stranded but most other work is solid wire. I do however like to use Ideal Pigtails for most connections as they are 12ga stranded copper with a forked connector so the connections can be pushed into the back of the box and there is less stress on the device.


Thanks woodchuck. I guess I should have mentioned that in my area, all work is required to be in EMT. I'm going to edit the OP to reflect that.


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## Tinstaafl

Stranded is certainly easier to pull. 

Electrically, there's some theory I learned decades ago--and don't know if it's been disproven or not--that says electrical current tends to travel mostly on the "skin" of a conductor. If that's truly the case, stranded would provide much more surface area for that flow and therefore be significantly more efficient.


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## mrmike

Great Question ! Having worked in Industry for many years-we used mostly all stranded wire & cable. Some advantages are it is much easier to pull in cable trays & conduit. It also seems to have a much tougher covering on it, unlike solid which cuts so easily. Another is a strands can be broken off & the rest are still there to conduct. On solid they break off completely & you lose connection,
On the downside stranded cable is much harder to strip. The conductors don't wrap around screws good, but we always used crimped connectors on them which IMO is even better. Another downside is a strand can be sticking out of where it should not & cause problems down the road- like one sticking out of a wire nut-which I have gotten a few shocks from........ Time for breakfast- hopefully we get more input..................


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## Leo G

Tinstaafl said:


> Stranded is certainly easier to pull.
> 
> Electrically, there's some theory I learned decades ago--and don't know if it's been disproven or not--that says electrical current tends to travel mostly on the "skin" of a conductor. If that's truly the case, stranded would provide much more surface area for that flow and therefore be significantly more efficient.


Absolutely true.


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## 480sparky

Leo G said:


> Absolutely true.


 
And this is why, when you drive by and look at an electrical substation, many of the conductors look like pipes.


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## Anti-wingnut

480sparky said:


> And this is why, when you drive by and look at an electrical substation, many of the conductors look like pipes.


Good point. I do not think it is necessary to involve physics when discussing wires. The if the UL and NEMA consider a wire as sufficient to carry a load, that's OK with me. 

In real numbers, what is the ampacity difference from say, 12 solid and 12 stranded? Pretty small I would guess


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## 480sparky

Anti-wingnut said:


> Good point. I do not think it is necessary to involve physics when discussing wires. The if the UL and NEMA consider a wire as sufficient to carry a load, that's OK with me. ........


Well then, let's throw Ohm's Law out the window.........


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## Anti-wingnut

My point is as far as conductors, there is no real difference between solid and stranded. It becomes more of a preference for the behavior of the wire as a working meduim. By that I mean pulling, stripping, connecting, and the longeviety of connections.


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## Winchester

on machinery, or places with a lot of mechanical stuff and vibrations we've always used stranded with crimp on connectors.










I used to work with a company wiring premade MCC control towers and stuff for gravel pits and tar sands, that were shipped in sections and reconnected on site. We used mostly all stranded and connectors like that in the buildings.

For the control circuits they were solid wire but they were all going into terminal blocks, relays, fuse holders etc.

95% of all other work I ever did (mostly residential) has been solid.


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## rselectric1

Interesting replies. Especially about the skinning effect.
Common sense would tell me that the electrons would "skin" to the outermost surface. (Including the assembly of all combined strands, thus making stranded and solid about the same)

Am I wrong?

It looks at this point that I am going to stick with solid 14's & 12's.


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## Winchester

rselectric1 said:


> Interesting replies. Especially about the skinning effect.
> Common sense would tell me that the electrons would "skin" to the outermost surface. (Including the assembly of all combined strands, thus making stranded and solid about the same)
> 
> Am I wrong?
> 
> It looks at this point that I am going to stick with solid 14's & 12's.
> 
> SMILEY AD REMOVED


Why is there an ad in your post? :blink:


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## rselectric1

Winchester said:


> Why is there an ad in your post? :blink:


?-The dremel ad? or am I missing something else. (I usually am:laughing


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## Tinstaafl

rselectric1 said:


> Common sense would tell me that the electrons would "skin" to the outermost surface. (Including the assembly of all combined strands, thus making stranded and solid about the same)


Well, anal-ytically, that's the outermost surface of a solid conductor. Stranded wire consists of several solid conductors, which at the atomic level are miles apart except at the ends where they're crimped or otherwise compressed together.

So in theory, the [majority of] current travel takes place in parallel, on the surfaces of all the conductors.

But Anti is right; you'd most likely never really notice the difference in efficiency between stranded and solid outside of a lab. So it basically comes down to whatever's most comfortable for you to work with.

For me, that would be stranded any time I have to deal with pulling the stuff through conduit, if there are any elbows at all involved. I'll gladly trade some fussiness at the terminations for less gruntin' & cussin' during the pull. :thumbsup:


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## 480sparky

rselectric1 said:


> ?-The dremel ad? or am I missing something else. (I usually am:laughing


 
Your SmileyCentral link. I think you copied the URL of the website itself and not the smiley you wanted.


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## DaveTap

For 12-14AWG might want to read the devices you you use... most screw terminals are not aproved for stranded and specifically "state solid wire only"


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## Smeric28

Whoa, i think this solid vs stranded and the skin effect is headed down the wrong path in a hurry. Yes there is a skin effect, some electricity also flows through the core of the wire. 14ga solid and 14ga stranded THHN are rated for exactly the same current capacity. stranded wire is just thinner overall and more flexable. We're not throwing ohm's law anywhere, it's already been figured out 

AWG as it is orginally defined relates to solid wire only. look up "American Wire Gauge on Wikipedia"


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## Ohmy

Is there not a price difference between the two? I always thought stranded was more expensive. In commercial and industrial work, we always used stranded. Its alot easier to pull 7 #12 strandeds through a 1/2 pipe than solid thhn.


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## JohnJ0906

480sparky said:


> 12 and smaller, solid unless specs or manufacturer dictates otherwise.
> 
> 10 and larger, stranded if at all possible.


# 8 and larger is required to be stranded if installed in conduit. 310.3


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## swebb

Tinstaafl said:


> Stranded is certainly easier to pull.
> 
> Electrically, there's some theory I learned decades ago--and don't know if it's been disproven or not--that says electrical current tends to travel mostly on the "skin" of a conductor. If that's truly the case, stranded would provide much more surface area for that flow and therefore be significantly more efficient.


I realize that this is an "old and dead" thread, but I came across it while searching and wanted to add some information for others who may stumble across the thread. 

The skin effect is in fact real and does matter, but is not a factor for choosing stranded vs solid for 12 gauge wire for low frequency A/C. I am not an expert on this topic, but the summary section on the Wikipedia entry seems good:

http://en.wikipedia.org/wiki/Skin_effect

"Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. T*he skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller*, thus reducing the effective cross-section of the conductor. The skin effect is due to opposing eddy currents induced by the changing magnetic field resulting from the alternating current. *At 60 Hz in copper, the skin depth is about 8.5 mm.* At high frequencies the skin depth becomes much smaller. Increased AC resistance due to the skin effect can be mitigated by using specially woven litz wire. Because the interior of a large conductor carries so little of the current, tubular conductors such as pipe can be used to save weight and cost."

(Emphasis added)

Practically speaking you can disregard the skin effect for anything you can get in solid core.


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## keirstitt

Much as i'm loath to contribute to such an old thread.

Skin effect is just about non-existent at 50/60Hz on 2.5mm^2 cross section cable or indeed just about anything you will find in a domestic or light commercial setting.

In addition. The difference in the skin effect between solid and stranded conductors is particularly small. When skin effect is an issue, engineers use litz wire where each strand is insulated from each other. This overcomes the skin effect as the current in the central conductors is unable to travel to the outer conductors.

in stranded cable there is no such insulation and hence skin effect is just as prominent as in solid core cable.

As for the observation about the use of hollow pipes rather than cable for some high current applications. This is normally done for other reasons such as allowing the passage of coolant.

If anything skin effect can be useful as one of many natural means to attenuate high frequency harmonics on the network.

Overhead power lines on the MV and HV networks are normally Aluminium Conductor Steel Reinforced. They are metallic all the way through - albeit with the inferior electrical conductor on the inside but I believe this is for structural and not electrical reasons.

Underground cables too rarely contain any centre hole.


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## rescraft

FWIW the only thing I can say for stranded, is that alot of sparkys don't realize that when making the connection to a screw terminal, you have to wind the strands counter clockwise when you make to shepherd's bend to screw it home.
That's all I got.


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## tjbnwi

rescraft said:


> FWIW the only thing I can say for stranded, is that alot of sparkys don't realize that when making the connection to a screw terminal, you have to wind the strands counter clockwise when you make to shepherd's bend to screw it home.
> That's all I got.


I wind the wire around the screw clockwise. I leave the insulation on the end also.

Tom


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## MarkJames

Was he talking about the direction of wire twist, not wrapping the screw?


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## tjbnwi

MarkJames said:


> Was he talking about the direction of wire twist, not wrapping the screw?


Why are you twisting the wire?

Tom


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## Leo G

Retwisting. 

I also learned that trick from a sparky. Leave 1/2" pc of the insulation on the end of the wire so it holds it together until the screw is tightened.


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## Inner10

All stranded wires that go directly under screws get sta-kons.

Sent from my Nexus 6P using Tapatalk


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## Golden view

The skin effect applies to much larger wires. Something like 5/8" diameter per strand.

Carry on.

edit: I didn't see page two of this thread. I'm a little late to the game.


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## Rmcooke86

Inner10 said:


> All stranded wires that go directly under screws get sta-kons.


I couldn't agree more. ? Only other alternative would be devices that provide a compression plate under the terminal screw.


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