If a correctly designed crimp tool is used, crimp connectors are extremely secure. Unfortunately, it's practically impossible to find a correctly designed crimp tool in big box stores or local hardware stores.
If a correctly designed crimp tool is used, crimp connectors are extremely secure. Unfortunately, it's practically impossible to find a correctly designed crimp tool in big box stores or local hardware stores.
UL: "14 AWG solid copper wire only."
On 11/13/2009 6:39 AM Pete C. spake thus:
You've made a convert out of me. From now on I'm going to use those receptacles, instead of the el cheapo wrap-the-wire-around-the-screw types.
It is actually a BAD idea, as it hardens the wire where the tinning stops, making the wire more succeptible to fatigue breaking of the strands. NOT ALLOWED in aircraft wiring, for one "solid" example.
Suppose I wanted to replace an 18-gage lamp cord. If it had 19 strands of 30-gage, like much automotive wire, it would probably screw down to the socket pretty well. But 18-gage lamp cord may have 41 strands of
34-gage. Twelve-gage zip cord could be worse; it might have 65 strands.It can be hard to get wire with a lot of strands to stay under a screw. What would be wrong with tinning? Within the lamp, strain and vibration shouldn't be problems.
If instead of a screw terminal, I wanted to use a wire nut on zip cord with a lot of strands, I might try tinning if I had trouble. I wonder if that would violate the NEC. (Some wire nuts will screw down far enough to clamp the insulated part of a cord.)
If there isn't a vibration or strain problem, then there is no problem that I see.
If I am joining zip cord, or stranded wire in a light fixture to 14 solid, I just strip the stranded wire longer than the solid wire and twist it around the solid wire first, then add the wire nut. It's always worked _great_ for me. I do make sure there is more of the stranded wire toward the end of the solid, it's just how I found it to work the best. Maybe it's not code if I strip the stranded wire longer than the strip gauge? I don't know. I do know that it works very well code or no code. Give it a try and you won't have to worry about tinning.
Just "hard twist" the wire and you are usually OK. IF you solder the end, make sure there is a strain relief close to the connection to prevent flexing of the wire near the soldered end.
Now I remember where I've tinned stranded wire: speaker wire! Some small-gage speaker wire has very fine strands. Tinning the ends makes it easier to insert it into the terminal on a receiver or speaker.
I discovered that the tinned ends made it easier to use wire nuts on speaker wire. I've also tinned stranded wire in electronics where I wanted to use a wire nut for a connection that could be done and undone as easily as a plug.
I've never tried this in a 120V circuit. I don't know if there would be drawbacks.
Most of my connections using stranded conductors are in vehicles, and the strands are usually stiff enough that I don't need pretwisting. It depends on the design of the wire nut. I try to screw the wire nut down onto the insulation for mechanical reliability.
Like you, I'll pretwist if the strands are so flexible that they get pushed out of the way of a wire nut. I use about 1/2 turn CCW. The wire nut twists the bundle CW, and the pretwist gives the wire nut a head start on that twisting.
I've used a wire nut on conductors whose strands were silky thin. It was the cord of a set of headphones, which I accidentally snipped with pruners. There were three conductors: left, right, and ground. I "spliced" each conductor by pinching it in a piece of masking tape, then screwed a live-spring wire nut over the whole thing.
The wire nut provided electrical reliability by squeezing the taped connections. It helped mechanically by clamping the insulated cords together. I've used those mended phones for ten years without trouble. Wire nuts can be very useful!
The real answer is in ther manufacturers instructions and how it was listed. Some may specify one wire size but I bet there are none that say 2 wires only. With that in mind a smaller wire on one side has to be better than zero so I doubt there are any that say "same size only" either. I know, on the Square D breaker, it says 1 or 2 wires from 8 to 14.
Just the ends?
When attaching line-cord (ordinary wire for lamps, etc) to those two screws, to keep the strands from coming "loose" and maybe shorting on the other side, I of course twist it tight, but then tin the end, before wrapping the end around the screw and tightening it.
Anything wrong with doing that?
Thanks!
David
Please say more.
Wiring a lamp socket, tinning just the last 1/4th or 1/8th of an inch, just to keep the strands from sticking out from where screwed down, surely that's ok?
And being screwed down hard, no flexing, I'd hope.
Seems to me that a strand coming loose within airplane wiring would be a lot more dangerous than tinning just a tiny bit at the end to keep a strand from sticking out, with who knows what effects.
Now, I am willing to be educated. Please don't just dictate the correct answer, but try to CONVINCE us via argument, data, metallurgy, whatever.
THANKS!
David
Worked at wiring broadcast studios, and we were not allowed to tin stranded wires.. It was said that solder is too soft, and after tightening down screws or clamps, the solder would just compress, and would eventually cause a loose connection.
Ray
He already told you why, with an argument based upon metallurgy.
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