Stranded Wire

[ramsy]

Here's two examples that I had laying around.

Thanks for sharing.

Solid wire crimps fall apart in my experience, using Yellow die for 12-10awg.

Perhaps solid-wire crimps pass UL testing, until the device is shoved into the box, or the wire bends, and deforms the crimp.

Maybe cheep off the shelf vinyl crimps wont reliably hold solid wire, when devices are pushed & pulled around.

 

[infinity]

Thanks for sharing.

Solid wire crimps fall apart in my experience, using Yellow die for 12-10awg.

Perhaps solid-wire crimps pass UL testing, until the device is shoved into the box, or the wire bends, and deforms the crimp.

Maybe cheep off the shelf vinyl crimps wont reliably hold solid wire, when devices are pushed & pulled around.

I agree that crimping solid conductors even with the listed tool doesn't make a great connection. Sometimes you have no choice like if you need a female disconnect crimp with solid wire and don't want to pigtail on a piece of stranded.

 

[Joethemechanic]

Thanks for sharing.

Solid wire crimps fall apart in my experience, using Yellow die for 12-10awg.

Perhaps solid-wire crimps pass UL testing, until the device is shoved into the box, or the wire bends, and deforms the crimp.

Maybe cheep off the shelf vinyl crimps wont hold solid wire?

I hate those vinyl crimps. So many years working on trucks and equipment and they are everywhere someone had their fingers. Never protected from the environment, and crimps look like they mashed them with vice grips.

Same guy that did that mess will call you a hack if you use a wire nut and tape it up with 88

I've seen well twisted and well wrapped splices far outlast those ugly blue things

 

[Eddie702]

Stranded is usually considered better. I have used solid when I got sick of THHN?THWN stranded curling up especially at the end of the spool but solid is no easier it has its own issues.

 

[winnie]

But one might argue why that is? Shouldn't solid hold more ampacity than stranded? In theory it has higher density?

Stranded wire of the same AWG has larger diameter than sold, precisely because stranded is less dense.

This has been challenged by physicists for a long time that electrons only travel on the outer rim of the wire

That is skin effect or skin depth, and is only significant at high frequency or for large diameter wire. The skin depth in copper at 60Hz is 8.5mm. This isn't a sudden cutoff but rather an exponential function. So you will have some skin effect in any wire, but it gets more pronounced the bigger the wire is, and isn't a big effect until your wire diameter gets larger than the 'skin depth'.

, then add conspiracy theory that copper mining companies are holding back data that wires are too oversized to begin with.... I don't know.

All the data is public...but I'm sure the CDA spins the data to maximize copper sales.

 

[Joethemechanic]

This isn't a sudden cutoff but rather an exponential function.

So on a graph, this is a curve and not a straight slope?

 

[jim dungar]

That is skin effect or skin depth, and is only significant at high frequency or for large diameter wire. The skin depth in copper at 60Hz is 8.5mm. This isn't a sudden cutoff but rather an exponential function. So you will have some skin effect in any wire, but it gets more pronounced the bigger the wire is, and isn't a big effect until your wire diameter gets larger than the 'skin depth'.

For 60HZ the diameter is between 250 and 300kcmil. I believe the NEC takes skin effect into account in its ampacity tables.

I majored in electrical engineering with an emphasis on power systems and machinery. I don't remember studying skin effect except as some esoteric anomaly. Yes it is a big deal for higher frequency applications, like radios and lightning mitigation.

I don't understand why basic electricity courses for new electricians spend more than 5 minutes on this topic.

 

[winnie]

So on a graph, this is a curve and not a straight slope?

I honestly don't understand the derivation of the skin depth equations well enough to have a good intuition for the shape of the current density in a wire. The wikipedia article ( https://en.wikipedia.org/wiki/Skin_effect )has a diagram shows current density vs depth for various ratios of skin depth to wire radius:

The number for each curve is the ratio of the skin depth to the wire radius. So 0.9 means that he skin depth is 0.9 * the wire radius; in a 60Hz system the 0.9 (red) curve represents what you'd see in wire 18.9mm (almost 3/4") in diameter. As I said, I don't have a good intuition for this derivation, in particular if the wire radius is > the skin depth, I don't understand why the current density is only slightly reduced. I'm not sure if this is because we are looking at a circular cross section conductor rather than a large flat conductor, or if there is some error in the diagram.

-Jonathan

 

[hbiss]

Solid wire is for homeowner grade outlets where you wrap the screw heads.

Lots of commercial and industrial grade devices require you to wrap the screw head also and I prefer solid with devices that have clamping plates. So don't say solid is for residential. I don't trust stranded with screw terminations unless you use crimp terminals. Good for pulling, but other than that stranded is twice as much work.

Wonder how the torque specs differ between solid and stranded?

-Hal