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Back-ground:

The wiring at the residence dates back a century - almost. The old wires were wound in cloth, and are pretty thick aluminium/tin-coated copper. The old energy meter (one with a marked wheel that rotates; mfr. Contimeter) was recently replaced with one of these new-fangled electronic digital ones. My electric load is unchanged. Yet the new meter appears to register easily double the old one.

Body:

Typical appliances that form the electric load are as follows -

  • Ceiling Fans
  • Lamps (Incandescent, Fluorescent, and Compact Fluorescent)
  • Television (old-fashioned CRT type)
  • Computer (with a similarly old-fashioned CRT monitor)
  • Micro-wave oven
  • Vacuum cleaner

The electrician says the old wiring should be replaced by newer 2.5 sq.mm wires; I believe this used to be called a 5/22 wire. He further recommends a multi-strand wire rather than one with a single core. What little I recall is that a multi-strand conductor is suited for HF/VHF and such applications. The supply line from the utility company is 240V@50cps.

Question:

Is a multi-strand conductor better suited for house-hold wiring than a single-core?

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1  
Are you really asking about stranded vs. solid? Or are you actually concerned about the apparent doubling in electricity usage? If the latter, then you need to call your power provider and have them check your meter. It's possible that your old one was broken our your new one is defective. –  longneck Jan 15 at 16:24
    
@longneck Yes (+: The question is really about stranded .vs. solid. The mention usage is merely for the back-ground as premised. –  Everyone Jan 16 at 2:00

2 Answers 2

up vote 6 down vote accepted

Stranded

Flexibility

Stranded wire is more flexible than solid core wire, which makes it well suited in situations where there will be movement of the wire. It also makes routing the wire through a building a bit easier.

Higher resistance to metal fatigue

Where solid core wire will weaken and break, stranded wire holds up to being bent repeatedly.

Solid

Cheaper to manufacture

While this savings may or may not be passed on to the consumer, solid core wire is cheaper to make.

More rugged

Solid wire resists cutting and stretching damage better than stranded wire.

Lower resistance

Given a solid and stranded wire of the same diameter, the solid wire will have a lower resistance. This is because there will always be gaps between the strands of a stranded wire. A stranded wire of the same gauge, will have a larger diameter than a solid wire to compensate for this. When you buy wire, you'll always buy it based on gauge. Both solid and stranded wires will have the same resistance, the stranded will simply be a bit larger in diameter.

Easier to terminate

If you're not careful when stripping stranded wire, you can end up cutting off strands (usually only a problem with smaller gauge wire, or wire with lots of strands). Depending on the number of removed strands, the ampacity of the wire can be negatively affected. Though nicking a solid core wire while stripping can make the wire more susceptible to breakage, so this isn't a clear cut advantage.

Solid core wire can be used in push in ("backstab") terminals, more often than stranded. This can be a pro or a con, depending on who you talk to.

Stranded wire can be more difficult to terminate on screw terminals, as you can sometimes have escapee strands which don't end up under the screw. This again can affect the ampacity of the wire.

Because stranded wire has a larger diameter, it tends to fill up twist-on wire connectors faster (less wires allowed in the connector).


Unless there's a lot of movement within the home (RV, house boat, frequent earthquakes), or you're pulling the wire through conduit. I'd say there isn't much of a difference either way.

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Lower resistance is misleading, because in comparing conductors of the same conductor cross-sectional area (same thing as wire gauge, just expressed differently) there is no difference. Overall wire diameter is not used to specify wires on either side of the planet. –  Ecnerwal Jan 15 at 14:04
    
@Ecnerwal Thanks, I've edited my response to make this more clear. I was really trying to point out that the stranded wire will be thicker, because it has to be. –  Tester101 Jan 15 at 14:09
2  
I have heard that current largely flows on the surface of a wire, rather than the core. If that is true, wouldn't stranded have a lower resistance because of the increased surface area for a given cross section? –  bib Jan 15 at 14:58
4  
@bib Not according to anything I've read. This idea seems to pop up from time to time, but it's quickly disproved. From Wikipedia "ordinary stranded wire does not reduce the skin effect because all the strands are short-circuited together and behave as a single conductor." –  Tester101 Jan 15 at 15:20
8  
@bib - Furthermore, skin effect isn't relevant at household wire gauges at normal frequencies. Skin depth is sqrt((resistivity of conductor)/(pifrequencymagnetic permeability of conductor*permeability of free space)). At 60hz in copper, that comes to about 8.5mm, so the skin depth is greater than the diameter of the wire and thus does basically nothing. You'd need to be using 00 gauge wire or larger for skin effect to even come into play. –  Compro01 Jan 15 at 18:21

The only advantage of multi-stranded wire (comparing wires of the same cross-sectional area) in household wiring is that it's more flexible than solid wire. That can make it easier to install in some cases, depending where the wires run.

Electrically, it makes no difference at all.

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