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.
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.
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
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!
Like everyone else said, stranded for flexibility pulling through
conduit and whatnot. For termination at receptacles and the like, get
the back wire type devices, not to be confused with the push wire type
which suck. The back wire have a hole you stick the wire in and then
tighten the screw which clamps the wire solidly. This is similar to
terminals in plugs and works well with stranded wire.
Yes, you can find them at 'Depot / Lowe's. They are typically the "Spec"
grade devices and a few dollars each vs. under a dollar. The entire
construction is better than the cheapos, better terminals, better
receptacle contact area and pressure and better more durable body. For a
given project the better receptacles will cost you and extra $20-$30,
pretty negligible for the significantly better parts.
AND, easier to attach a wire to, and a more reliable attachment.
Proly actually cheaper, from a net cost (labor) pov.
Push-wire devices ought to be made illegal. Fires waiting to happen, imo.
Esp. push-wire devices used with stranded! That *has* to be illegal, no?
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
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.