#10 - #12 AWG Stranded Wire?

[peebee]

NEC requires most conductors #8 AWG & larger to be stranded. For #10 & #12, stranded or solid can be used.

However, I've never seen stranded used for #10 & #12 (only one exception ever to this). #10 & #12 are almost ALWAYS solid.

I understand that there's essentially no cost difference between stranded and solid.

So -- how come stranded wiring is not used more often for #10 & #12 wiring?

 

[mpparent]

Well..from my experience...it's just been easier to use solid. Putting stay-cons on #12 or #10 just to terminate it is a pain in the butt.

Mike

 

[Laplacian]

Our company uses stranded conductors for all power/control wire for reliability. Over time, solid conductors become brittle and often break while troubleshooting in field junction boxes.

 

[GOTWW]

It is a matter of choice for some electricians, There some that prefer stranded for the pulling aspect and that the crimp-on connections work extremely well. The crimp-on connections are lousy with solid wire, but I thing the wire-nuts work better on solid as opposed to stranded. I think that you need special (listed) wire nuts with stranded wire though.

 

[alehman]

I specify stranded only for control wiring. Sometimes contractors elect to use stranded for general wiring also, particularly when pulls are difficult.

 

[mc5w]

Most of the #12 and #10 that we pull into conduits is stranded. If there are 2 neutrals then sometimes one will be solid.

The primary advantage of solid is that you only have 1 strand to clean with #220 silicon carbide abrasive paper as recommended by the Consumer Product Safety Commission which is a variation of the old Signal Corps method. The reason why you see electrical systems from WW 2 is that there was not enough copper to go around, therefore you had to have ALL the wire strands conducting. For more information go to Dr. Jesse Aronstein's website

http://www.inspect-ny.com

 

[dpc]

In most industrial applications in the US, solid wire is used only for lighting and receptacle circuits, with all other applications being stranded.

The twist-on "wire-nuts" used for fixture and receptacle wiring work well with solid wire and generally solid wire will be less expensive.

 

[EEJaime]

Our specifications call for #10 and #12 AWG wire to be solid. We find that solid conductors in these smaller branch circuit sizes tend to be more reliable, easier to terminate and can withstand a little more force from the stripping and termination,whereas stranded, although easier to pull and more flexible in boxes, etc..., is a little more delicate and requires more caution in it's installation. Also for light commercial work, if "stab-in" terminations are used, solid provides a better connection. Both are effective conductors, some distributors carry only limited colors of one or the other, so if we have a system with different phase color schemes for 600v, 480v, 208v, etc..., one may be more readily obtained than the other.

Electrically, there is little difference in power circuits. I know that control panel builders prefer stranded for it's ease of training and lacing and it's flexibility.

 

[jraef]

I think the issue here peebee is that it depends upon the application.

From your viewpoint you never see stranded being used, so I assume that you are primarilly referring to lights and receptacle wiring for the reasons mentioned above.

For those of us in the industrial world, it would be almost the opposite. We RARELY see solid wire being used for anything other than signal wires and low voltage systems (under 50V) like alarms or instrumentation where it is 18ga and smaller. Industrial common practice precludes the use of "wire nuts", favoring terminal blocks or crimp-on pressure connections that do not work well with solid conductors.

"Venditori de oleum-vipera non vigere excordis populi"

 

[resqcapt19]

We never use solid #10. The installation labor is too high. We use solid 12 for commercial work, but not industrial.

mc5w,
I've never seen copper conductors cleaned with silicon carbide abrasive paper unless the conductor has corrosion damage. The CPSC website information pertains to the use of aluminum conductors, not copper.

Don

 

[mc5w]

I goofed my previous post slightly.

Resqcapt19, Dr. Jesse Aronstein says that my grandfather ( who was ex-Signal Corps ) trained me well and that it is appropriate to clean copper wires with silicon carbide paper when new. Thanks to catalytic converters copper wiring that is outside burns up just as fast as aluminum unless both metals are cleaned and treated with joint compound. If you read his directions you have to clean both the copper wire AND the aluminum wire when connecting the two together.

Dr. Aronstein also ran some different tests of copper to copper connections as well as copper to aluminum and aluminum to aluminum. In all cases the wires that were not cleaned with silicon carbide paper or diagonal cutters burned up well before the ones that were cleaned. That is, the Old Signal Corps method plus electrical joint compound is the best method and cleaning the wires but not applying joint compound is second best but still vastly superior to not cleaning the wires.

He also ran some tests that showed that "cleaning" aluminum or copper wire with a wire brush is completely ineffective.

I am facing the task of replacing 18 compact fluorescent lampholder that are 2 years outdoors in November weather. The reason why is that the manufacturer never bothered to clean the #18 solid copper wire and apply Ilsco Deox(R) to prevent corrosion. The fixtures face Woodland Avenue ( a main drag ) in Cleveland, Ohio.

A year ago an indoor system started having problems with failures in solid #12 copper wire that was 27 years old because the installers never bothered to clean the wires like old timers did. This was an ordinary indoor environment. The reason why you see 60 year old electrical systems that are still going strong is that the old timers had to have ALL the wire strand conducting because there was not enough copper to go around. You could not substitute 750 KCM for 500 KCM because only 2/3 of the wire strands were conducting.

 

[resqcapt19]

mc5w,
I've never seen a manufacturer's instruction or a design spec that required copper conductors to be cleaned prior to termination. Is this a commom practice?
Don

 

[peebee]

I believe that all of mc5w's posts regarding sanding & cleaning wires applies ONLY to aluminum wiring or aluminum/copper splices.

Copper/copper splices generally do not require such cleaning.

mc5w please correct me if I've misunderstood.

Aluminum wiring ALWAYS requires such cleaning as it Al oxidizes nearly instantly upon contact with air; the resulting oxide is essentially a non-crystalline sapphire, which is highly resistive. These high-resistance splices are the cause of fires associated with aluminum wiring. To prevent the fires, aluminum MUST be sanded AND coated with an anti-oxidant joint compound. Aluminum/copper splices MUST be made with listed ALCU connectors. Nothing new here, this was all recognized some 20 years ago.

 

[jghrist]

From Anderson connector and fitting catalog reference data:

Installation Recommendations for Bronze and Copper Connectors:

Bronze Bolted Connectors - Contact sealants are not normally required in copper connections. However, the use of sealant is recommended in severe corrosive environments and direct burial applications such as ground grids.

Vigorously clean the conductor and connector contact surfaces with a stainless steel wire brush.

Alternately and evenly tighten bolts with a torque wrench to the values shown in Recommended Torque Values table.

 

[jraef]

jghrist,
What you are refering to is valid for larger cables that would use bronze connectors such as those made by Anderson. Look however at the topic of the post. We are talking about #10 and #12 wire, not cable.

"Venditori de oleum-vipera non vigere excordis populi"

 

[ck]

mc5w is correct-both copper and aluminum wire should be wire brushed and an oxide inhibitor applied. It is good workmanship and results in a connection that resists corrosion due to moisture or corrosive environments. Both copper and aluminum oxidize, and both metal oxide layers are nonconductive. Studies and field installations have shown that in normal conditions, neither copper nor aluminum connections fail in the absence of oxide inhibitor with otherwise proper installation. Where you have problems is with the introduction of corrosive fumes or poor installation practices such as improper torque or incompatible connector/conductor combinations.
The CPSC site states that the failure of aluminum wiring used in the 60s and 70s was due to "... the differing thermal and mechanical properties of aluminum and the metals used in outlet contacts."