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Solid vs. Stranded wiring?

peteduffy's picture

I was told today that stranded 10 gauge copper wire will carry more current than solid of the same gauge and material.  Is this true?


Thanks in advance.


Pete Duffy, Handyman

Pete Duffy, Handyman

(post #95255, reply #1 of 15)

NO!

In fact look in the tables stranded is about 3% higher resistance than solid.

Now there is something called skin effect so that higher frequencies the current only flows on the outter surface of the wire. Stranded has more surface area and thus less resistance.

BUT, that only had much affect at RF frequencies.

. William the Geezer, the sequel to Billy the Kid - Shoe

(post #95255, reply #2 of 15)

What Bill said. The only reason for using stranded is that it's more flexible. And in standard home wiring situations it's harder to terminate reliably, so solid is usually better.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #95255, reply #3 of 15)

I read a good discussion of stranded vs solid; this was regarding cat5 cable.  If it's in the walls, stationary, you want solid.  It has lower resistance, is generally better.  But for the patch cables from the wall to the computer, you want stranded:  it's more flexible.


Same thing applies with power:  stranded is more flexible, so if it's an application where it will be moved a lot (extension cords, etc), use stranded; otherwise, use solid.

(post #95255, reply #4 of 15)

Thanks for the info, folks.  Pretty much what I thought, too, but I wanted some confirmation.


The application is a poolhouse ( 3 pool lights each 250W 12V, switches wired between the panel and the transformer) run in conduit (EMT).  Short runs (poolhouse is only 16x30, so the total run is about 20' with all the bends, in 3/4" EMT).


No high frequency concerns with this.  I'll inform the GC on his error in thinking.


Not going to redo anything, but just want to set him straight.


Pete Duffy, Handyman

Pete Duffy, Handyman

(post #95255, reply #5 of 15)

Keep in mind that stranded is commonly used in conduit because of its flexibility. In any sort of complicated run solid wire would be impossible to pull.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #95255, reply #6 of 15)

I agree.  But the runs were short, and with the help of a fish tape, got them through OK.  He used stranded, and I had to move some switches that he put in the wrong spot, and all I had was solid, so I used it.  He told me I should have used stranded because it can carry more current, but I wanted to double check the facts here.

Pete Duffy, Handyman

Pete Duffy, Handyman

(post #95255, reply #7 of 15)

When I was in grade school, a classmate's electrician father came in one day to do a presentation on electricity.

He had samples of wires, some solid, some stranded.

I had to ask why the difference....

He brought me and his daughter up to the front and handed me a stranded wire and her a solid and told us to bend them until they break.

A race I lost. Indeed, I never finished.

Rich Beckman

Another day, another tool.

(post #95255, reply #8 of 15)

As others have posted, 10 gauge is 10 gauge. The ampacity tables make no distinction between stranded and solid. Because, at 60 Hz (essentially DC), it makes no difference. If you are trying to conduct lighting (an infinite number of frequencies or radio frequences (up to a limit) stranded works better (ever look at co-ax?). And at really high frequencies, you don't use wire - you use wave guides.

At 60 Hertz: stranded is easier to pull. Solid doesn't have stray little wires that might short to another terminal. Therefore you have to be more careful with securing stranded to a terminal. You must pull much harder with solid.

Ampacity is the same.


David Thomas   Overlooking Cook Inlet in Kenai, Alaska

David Thomas   Overlooking Cook Inlet in Kenai, Alaska

(post #95255, reply #9 of 15)

Pete,

Here is a simple test for your friend.

Cut off a section of both solid and twisted 10 AWG wire. Take a look at both ends. One is solid, the other is not. The twisted wire has voids throughout its diameter where each strand touches other strands.

Which has the greater true area? True meaning that area which directly affects conductivity or 'ampacity'. Ampacity is a measurement of how much current a wire can safely carry. Ampacity is DIRECTLY related to the area of the the conductor in question.

Back to the solid and twisted wires. The area of of the twisted wire is derived by summing the area of each of the strands. When this is compared to the area of the solid wire - you guessed it - the area of the stranded wire is less than the area of the solid wire. The loss of area in the stranded wire effectively reduces it ability to conduct current . Solid wire does not suffer this loss and that is why solid wire is the best conductor of electricity.

In using heavier wire than 10 AWG you will find twisted wire used almost exclusively and this is due ( as was already stated in another post) to its inherent flexibility. Solid wire in heavier gauges are impractical for this very reason.

12 AWG is no fun to work with and much less so 10 AWG. However, the wire is matched to the breaker utilized in the circuit so oftentimes the use of 10 or 12 AWG wire must be used due to the appliance(s) being wired for. Twisted wire termination is not as clean as using solid wire. This was mentioned as well.

When wiring 'by the book', either will work fine because the normal NEC practice is to load a circuit at no greater than 80% of the breaker capacity.

Good luck.

Phillip

(post #95255, reply #10 of 15)

It depends on if  you accept electron flow theory or hole flow theory.

(post #95255, reply #11 of 15)

Re: " was told today that stranded 10 gauge copper wire will carry more current than solid of the same gauge and material.  Is this true?"


Yes. It is true but the difference is infinitesimal. Of no significance in any but the most exotic of situation. In a practical sense they are electrically identical in any residential, and most industrial, situations. I will say that most electricians will go with stranded for #10 or larger as it unreels, feeds and pulls easier. Often, in short runs, the difference between my being able to work alone and having to have help.


That said stranded, as pointed out previously, is a bit more difficult to terminate on small connections but even here a little planning can simplify this.


News: Pamela Anderson, and her two close friends, have become naturalized US citizens. You suppose she gets three votes?

(post #95255, reply #12 of 15)

There is very little "natural" about Pamela; if she became naturalized citizen, does that mean her implants have been removed?

(post #95255, reply #13 of 15)

I was trying to figure out what Pamela had to do with this thread but then I figured out the code of random word deletions in your post. Very clever!


I broke it down for those who might have missed it:


Yes. the difference is infinitesimal. the most exotic of identical in residential. most electricians will go with larger as it pulls easier. Often, the difference between my being able to work alone and having to have help.


That said pointed is a bit more difficult on small connections but even here a little planning can simplify this.


News: Pamela Anderson, and her two close friends, have become naturalized US citizens. You suppose she gets three votes?


Kevin Halliburton


"Do you see a man skilled in his work? He will serve before kings; he will not serve before obscure men." - Solomon

 

 

If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again

(post #95255, reply #14 of 15)

LOL.


 

I am a practical hands on (post #95255, reply #15 of 15)

I am a practical hands on person.  Here are the facts.   I ran a 1.5 horsepower table saw using a 100 ft 12/3 gauge extension cord.  The extension cord utilized stranded wire.  The motor struggled to start and stalled easily when using.   Next I ran the same 1 .5 horsepower table saw using 12/3 gauge solid wire.  With the solid wire the motor started easily and ran without stalling.  So, using practical experience and not "book derived information". I am saying solid wire has a greater current carrying capacity and less resistance than stranded wire.   I'm sure there will be comments refuting this and second guessing Connections etc. But  I assure you both cords used the same end connectors and the cords were laid out exactly the same.  As far as those saying the cord must have been less than 12 gauge, I assure you it was commercial grade 12 gauge so cord.   I now use solid core wire for any application where Current carrying capacity might be an issue.  The only advantage I can see for stranded wire is flexibility in applications where that is a requirement.