Wire Nuts, pre-twist vs. not

[Torque1st]

Send your sample, but then even a pre-twist will fail when 225# is hanging on it. A test like that proves nothing.

I have seen the failed connections in the field both by homeowners and professionals. Some professionals with many years of practice may be able to make a good connection every time but Jo Blow will not be able to. I have seen the failures. Even with practice and skill, I still feel a professional should do everything in his power to makes sure his connections are good, which includes pre-twisting for a visual inspection.

 

[walrus]

Send your sample, but then even a pre-twist will fail when 225# is hanging on it. A test like that proves nothing. .

I wonder how they do test connections? Seems to me if you could hang off a wire nut connection it proves it isn't coming apart. IF it can't come apart the individual wires must be in contact with each other.

 

[south pier garage]

I don't know how anyone would nick and break wires by pre-twisting. The portion that gets held in the lineman's pliers is cut off.

i have seen fellows strip wires with the cutting edge of their pliers. this can nick the conductor and leave a weak spot

 

[mmg440]

Used to twist now I don't, I really haven't seen much difference in original integrity. I find rework on pretwisted wires makes it more difficult to add or reconfigure circuits latter. Untwisting and retwisting with new conductors added just turns into a mess. I think the main thing with a wire nut connection is all the wires conductors are in fully and mechanically fastened tightly. I don't see that a little spiral of the wire inside will aid much in it integrity if properly done. I have seen both ways were a wire had come out or seemed loose.
This is a debate that could on for at least 100 more posts.
What if you are wire nutting two stranded wired or one stranded to a soiled wire? Does anyone know what would works better or are there two schools of thought there as well?

 

[porschedude996TT]

If you stand back and forget the long history of them working, and know anything about joining to two pieces of metal, then you have to admit that wire nuts in general are a real weak link in the system. The two pieces of metal are not really joined, they are "In Contact" with one another and there can be problems although few. It is like holding the frame members of my truck together with C-clamps rather than welding... I have never like them and feel that twisting them may give them more surface contact. I can appreciate that removing and modifying them after they are twisted can lead to wire failure. I also have concerns with the speed wire connections on some receptacles’; I don't feel they make enough contact inside the receptacle housing. I always loop the wire and use the side screws.

In my aerospace field we annually check and certify out wire strippers to ensure that the strippers don’t nick or mark the conductors. We also certify technicians annually to perform these tasks of stripping, soldering, wire-wrap, wire harness fabrication, and fiber-optic junctions.

Sorry the ramble on…

 

[nate379]

I think it's just preference. I do know the electrician that did work in my house did a **** job. A few of the pigtails in outlets I've moved, etc had loose wirenuts.... like I pulled the wire out and pulled the nut off by hand without untwisting it.

 

[Torque1st]

I wonder how they do test connections? Seems to me if you could hang off a wire nut connection it proves it isn't coming apart. IF it can't come apart the individual wires must be in contact with each other.

If you do some digging you can look up the listing number. Sometimes it is on the package. With the listing number you can sometimes dig out the relevant standards at UL -IF they have been published. Those standards organizations make money from the publication of their standards. There has been legislation around that has called for those standards to be made available to the public if they are called out or referenced in public documents (like building codes). The organizations (UL, NEC, ASME, etc) are resisting that effort strongly and they have lots of lawyers.

As far as fastening stranded to solid, or stranded to stranded, and fine stranded to course stranded or solid there are methods available. I have outlined methods of doing that securely in other threads and I don't wish to repeat myself when that info can be found with a search.

 

[Terry Kennedy]

If you stand back and forget the long history of them working, and know anything about joining to two pieces of metal, then you have to admit that wire nuts in general are a real weak link in the system. The two pieces of metal are not really joined, they are "In Contact" with one another and there can be problems although few. It is like holding the frame members of my truck together with C-clamps rather than welding...

True, but consider the reliability of wire-wrap (somebody's trademark, I'm sure, but now genericized like xerox, kleenex, etc.).

This is a square metal post with wire wrapped around it by a hand or power tool. The corners of the post cut into the wire and form a (hopefully) gas-tight seal. Older computers (not really old ones, but ones like the DEC PDP-11 and Data General Nova) had thousands (or even tens of thousands) of these connections and had overall excellent reliability. There were some issues (the normal metals were tinned posts and tinned wires; some bright boy got the idea to use silver-plated wire which introduced dissimilar metal problems).

This doesn't really relate to twisting or not twisting wire nuts, but I thought I should stick up for contact connections.

 

[Torque1st]

I still have wire wrap sockets, wire, and tools, as well as a few devices using them. All of my wire wrap sockets have gold plated pins tho.