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Old 01-19-2008, 10:46 AM   #1
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Stranded wire on screw connections


For general wiring of residential branch circuits. there does not appear to be any restriction (as far as I can tell) in using stranded wire over solid (it does cost a bit more but it's much easier to pull through pipe). However, terminating stranded wire at the screw terminal on a switch seems to present a challenge when compared to using solid. An electrician that I used to know showed me a technique where you cut the insulation around the wire using the stripper. You then begin to remove the insulation but stop short of completely doing so, leaving about 3/4" of bare wire exposed. The strands are twisted slightly and then bent to fit around the screw. The piece of insulation is left on the end of the wire to prevent the strands from spreading/feathering.

I've had some sucess with this method however often times, the twisting of the wire prior to bending/terminating encourages the piece of insulation to fall off. Not to mention, you have to be careful not to leave too much wire extending beyond the screw.

Is this practice OK? Is there a better way to do this? Although it seems like most of the receptacles that I buy allow you to back wire, which presents no similar issue when using stranded wire, I have not seen switches being manufactured with a means to back-wire.

Any insights are always appreciated!

Jimmy

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Old 01-19-2008, 11:04 AM   #2
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Stranded wire on screw connections


Trim a little more insulation off the end since when twisted, the end shortens. Also feel free to let the end be too long and stick out a little so long as the end doesn't come close to a different contact or terminal. Twist it tightly, as many spirals as you can without kinking the end.

Clamp in back wiring also requires that the strands be twisted to reduce loosening due to self squishing of the bundle following initial installation.

I like to tin the ends i.e. soak them with solder, which makes them essentially like solid wire. But usually I don't have a soldering iron handy.


Last edited by AllanJ; 01-19-2008 at 11:09 AM.
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Old 01-19-2008, 11:17 AM   #3
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Stranded wire on screw connections


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I like to tin the ends i.e. soak them with solder, which makes them essentially like solid wire. But usually I don't have a soldering iron handy.
I've often thought of the tinning idea but since I've never seen an electrician do it, I figured it was wrong and I'd be severely beaten for it!
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Old 01-19-2008, 11:59 AM   #4
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Stranded wire on screw connections


I don't think you will see tinning of the stripped end very often at least not by an electrician in a production environment.....

You can crimp on spade connectors if you like when installing switches. but use the correct crimping tool not pliers.....

Receptacles that are backwired are the way to go for stranded wire.

The insulation trick you described is by far the most common by commercial installers.

There are some electricians using the Wago connectors for smaller guages instead of wirenuts for stranded then they come out of those with solid wire to the devices.
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Old 01-19-2008, 01:08 PM   #5
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Stranded wire on screw connections


ANY way is acceptable but the BEST way to do it is to simply use a fork terminal.

Also, if you don't have forks available, twisting the stands tighter helps it stay together under the screw.

You can also split the strands in two, twist them individually and make a fork.


Quote:
I've often thought of the tinning idea but since I've never seen an electrician do it, I figured it was wrong and I'd be severely beaten for it!
Only if I was paying you by the hour Install fork terminal= 20 seconds. Tin the wires = ???? 5 minutes???

Last edited by 220/221; 01-19-2008 at 01:12 PM.
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Old 01-19-2008, 01:45 PM   #6
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Stranded wire on screw connections


Actually, the way that has worked for me for years is similar to what you describe. Simply take the piece of insulation on the end in your pliers and twist the wire COUNTER clockwise. Do this until the wire is tight, then terminate.
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Old 01-19-2008, 02:17 PM   #7
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Stranded wire on screw connections


I always use spade terminals and a crimping tool.
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Old 01-19-2008, 02:42 PM   #8
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Stranded wire on screw connections


Thanks for all the replies!

I had always wondered about rings or forks. I mean, they use them all the time in industrial control wiring but I haven't seem them used widely in residential. Certainly the forks would be easier than using rings and I've noticed that when you remove the screws, it takes a little fiddling to get them threaded back in.

At one time I had scoured the NEC trying to find an article that excluded their use but came up with nothing.

FYI-I bought a couple of Leviton Decora 3 and 4 ways today for my living room/front hallway remodel. The 4-way has a true back wire feature (not a back stab) but the 3-ways only have back stabs. So, the information will come in handy for the wiring of the 3-ways!

Stub-Don't worry. We use ring terminals on all our wiring at my workplace so I'm totally set with crimpers. On the other hand, I have seen what typically happens when someone tries to crimp with a standard set of pliers .

As far as soldering is concerned, I would think that a 250-300W gun would make short time of it. But yes, time is money and crimping would win any day in a production/contract environment. On the other hand, I'm my own labor so I can fart around all I want (at least to the extent that my wife doesn't come after me with the frying pan!).

Again, thanks to everyone!

Jimmy

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