Joining solid and stranded wires

Discussion in 'Electrical Forum discussion & Blog' started by Mikey, Feb 21, 2008.

  1. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    How best to join #10 or #8 wires in a junction box, where one is stranded, and the other is solid? I've seen some pretty mangled stranded wire in wire-nuts, tinned stranded in wire nuts, and split bolts. All have pros and cons -- what's right?
  2. Cass

    Cass Plumber

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    A small C clamp squishing them all together and then wrap it all in electrical tape...:D

    This is a DIY forum isn't it.
  3. frenchie

    frenchie Jack of all trades

    I remember reading somewhere, that you're supposed to twist the stranded around the solid, then bend the whole set over before applying the wire-nut. Seems like that'd be pretty awkward, though, and I've never seen it done that way.

    I think the trick to having the stranded not get slid back on the solid, is to have the stripped part of the stranded a little bit longer than the solid, so it catches the nut before the solid engages.

    I've also noticed that electricians use a slightly different wire nut on stranded - it's longer, and the plastic housing's made of a more flexible plastic - not sure what they're called, or how they're different inside, though.
  4. Spaceman Spiff

    Spaceman Spiff Architect

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    I usually twist the strands on the stranded tighter with a pair of pliers so that they don't splay apart in the wirenut. Then place the straight wires (no pre-twist needed) next to one another, and twist the wirenut on until you have one twist of the insulated part of the wire below the nut. I went to a 3M class and this is what the feller taught us. It is also surprisingly similar to the instructions for Ideal brand nuts.

    It says that pretwisting the strands isn't required (just no stray strands) but it seems more solid to me. Double check the connection by trying to pull the nut off the wires. None of it should move. Sometimes I have the stranded pull out and the solid stay, so then I redo it.

    Hope this helps.
  5. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    I thought of a pair of vise-grips and duct tape, but this would be cheaper. A local buddy just said solder everything together, but somewhere I read/heard that the NEC frowns on solder.
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

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  7. What did you do with Gary's eyes ?? [ the snail cat from Spongebob tv cartoon show ]

    but really that sound like someone have alot of free time to wrap the tape on the splitbolt like crazy i did see it few of them.

    Merci, Marc
  8. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    Hold the stranded wire slightly longer than the solid so it goes in to the wirenut first. Then hold both wires with a kung fu finger death grip so one doesn't push out.
  9. Chris75

    Chris75 Electrician

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    Location:
    Litchfield, CT
    I personally just buy wirenuts that are rated for the correct size and amount of wires...
  10. Bill Arden

    Bill Arden Computer Programmer

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    Location:
    MN, USA
    Sounds good.

    -
    But I have a off topic question...

    What's wrong with solder?

    I've twisted and then soldered stranded wire to solid in a 12Vdc BattleBot(n).

    I haven't ever done it in house wiring, but I am curious...

    One thing I do know is that simply soldering the stranded wire itself does not make it the same as a solid wire due to "creap" in other words the solder will slowly flow and loosen over time.

    I am guessing that since soldering just one wire could cause a problem they don't like solder at all.
  11. Cass

    Cass Plumber

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    5,980
    Location:
    Ohio

    I hope they used this for the tape balls [​IMG] to be sure it was safely secured.
  12. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    I believe the wire can heat up and melt the solder, but I'm not sure. It also has a tendency to crack when exposed to vibration or movement.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Off-topic, but somewhat related and interesting (If you're a geek)

    Most of the electrical solders melt in the low to mid700-degree range, if I remember right. In a fire, if it got that hot, it would mess up other things, as the insulation would be gone and any wood around would have also reached the ignition point. A cold solder joint can easily break, a proper one, just like on a pipe in plumbing, is very robust. But, I've been certified to solder things on missiles, so have some experience putting elecrical things together with solder! The average person probably wouldn't do it "right", to allow a long-term, successful connection. A lot of the stuff we make has to work first time out of the box after sitting around for maybe decades.

    The big bugaboo for awhile in the electronics industry is the growth of tin whiskers and it shorting out circuits. Not an issue on large-scale stuff, but a real pain on micro-sized things. So, tin and solder are a problem in electronics.

    One group I work with was discussing whether they needed an 18 or a 24-layer circuit board to optimize the design...can you imagine the tolerances to get connections inbetween layers?! and still have room to mount components on them? A tin whisker would spell death to it - they grow and short things out.
  14. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    There is nothing mechanically wrong with solder but in field work, do you want to install a wirenut and move on or drag and exrension cord and soldering iron around?
  15. hj

    hj Moderator & Master Plumber Staff Member

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    solder

    One problem with solder is that they might use acid core solder and then there would be a corrosion problem down the road.
  16. Bob NH

    Bob NH In the Trades

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    Location:
    New Hampshire
    When I wire-nut stranded to solid (often with fixture wires, and the fixture wires much smaller than the solid) I put a couple of small zig-zag bends in the solid before I spiral-wrap the stranded (stripped a little longer) around the solid. The tapered thread of the wire nut clamps the stranded to the solid and the bends prevent the solid from being pulled out.

    I can reliably attach #16 or #18 fixture wires to #12 solid and never have them pull apart.
  17. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    Location:
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    It's actually more around 370 degrees. If you have a poor solder joint, perhaps cold or weak, it could end up with enough resistance to heat it up.

    Jason
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