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If stranded wire can carry more power for a given wire gauge, why are homes typically wired using solid?

If solid wire is less expensive to make, that provides a compelling reason why solid is used, but if an electrician or homeowner wanted to use stranded, is there any reason not to?

For this question I am mainly referring to legs of U.S. home wiring for 15 and 20 amp breakers carrying 120 volts on a single phase.

JYelton
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4 Answers4

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A few reasons:

  • Stranded wire is more expensive to make.
  • At a given wire gauge, stranded is going to be larger than solid wire (it's the cross-sectional area of conductor that counts and there are going to be some air gaps between conductors with stranded). This could make a big difference if you have several cables in a limited space like an electrical box.
  • The main advantage of stranded is that it's more flexible. You generally don't need this in home wiring because it's all put in place once and hidden behind walls/floors/ceilings.
  • When you screw a solid wire into a switch or receptacle, you can tell if it's secure. I could see individual strands coming loose as you fold wires back into an electrical box.

More information in Wikipedia: http://en.wikipedia.org/wiki/Wire#Solid_versus_stranded

Niall C.
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20

The skin depth for copper wires is roughly 1/3" for 60 Hz. So unless your wire is more than 2/3" in diameter (YIKES!), it won't come into play.

Therefore, solid copper wire CAN carry more power than stranded wire at 60 Hz, due to packing inefficiencies (empty space) that is inevitably between the individual strands.

Doresoom
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3

Stranded is more susceptible to corrosion due to more surface area.

David E Robertson
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For AC - electrons run through entire cross-section the of wire

For DC - electrons like to run on the outside of the wire so stranded will have more surface area for a given gauge

John
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