Multiple conductors in terminals - installation method
- Thread starter pls1
- Start date
Sponsored Links
Exactly - and a fascinating document, Thanks!
As it says (exatly as I was taught) "To make a splice that will conform to the requirements of the National Electric Code, it must be mechanically and electrically secure without solder". That's how I was brought up in relation to soldered joints in electronics, but that was, of course, largely in the pre-PCB days. With PCBs one has little choice but to rely on solder - although, to this day, if I'm wiring manually on a PCB I will usually at least 'splay out' the leads of a component a little to produce some degree of mechanical retention before I solder it.
I've seen electricians just lie two conductors side-by-side (maybe with a little fine wire wrapped around to keep them vaguely in place during soldering) and then 'stick them together' with solder, and I have shuddered on behalf of those who taught me and would be turning in their graves
Kind Regards, John.
When that is the case then why the need for solder - genuinely interested.
Basically just to stop the mechanical joining (twisting, splicing, knotting or whatever) falling apart. The important thing (at least, as stressed to me in my youth) was that the electrical continuity should be the result of conductor-conductor contact (maintained by the presence of solder) and that one should not in any way rely on electrical continuity through the solder.
As a mechanical analogy, you could think it terms of a join in a rope, steel cable or whatever achieved by a 'hook and eye' sort of arrangement, which could easily fall apart. Put some tape around it to stop the hook coming out of the eye and the joint becomes much safer, even though the tape would take none of the strain. ... don't forget that, like tape, solder is pretty weak.
Kind Regards, John.
Sponsored Links
Another possibility is that the strands might rearrange themselves (perhaps due to flexing just outside the terminal) after the terminal has been tightened, and that might have a greater effect than the 'creep' of a single conductor over time.
However I think we're agreed that it's of academic interest only.
And also to provide a hermetic seal for the twisted/spliced joint to prevent oxidisation from increasing the resistance of the mechanical joint. in the early days of using wire-wrap terminations (remember those John?) we were taught to seal them with an inert grease.
Hmmm. I accept the tape analogy but if mechanically and electrically secure - just belt and braces I suppose.
Ah. That's more like a good reason.
Agreed. There are so many unknowns and variables that the answers, primarily of academic interest, could only be determined empirically.
Anyway, to put this all in perspective, of all the shapes and sizes of cables, solid conductors are only encountered in (some) 1, 1.5 and 2.5mm² ones. I still wonder why that happened with the change to metric - do you think it was just a matter of manufacturing cost? Is it the same in other countries? (where's Paul?
)Kind Regards, John.
Going back to the terminations -
if there were a problem I would think the manufacturers would incorporate a piece of metal which was pushed onto the wire by the screw rather than the screw itself digging into the wire, as they do in very small accessories.
if there were a problem I would think the manufacturers would incorporate a piece of metal which was pushed onto the wire by the screw rather than the screw itself digging into the wire, as they do in very small accessories.
Well, there's secure and secure. A joint totally reliant on twisting/ splicing/ knotting/whatever could fall apart if it got waggled about a bit, and solder prevents that. A non-conductive resin or varnish (I think shellac was once used for this) would probably do the job almost as well as solder - as I said, one is not meant to rely on any conductivity through the solder.
Kind Regards, John.
Agreed. I not only remember wire-wrapping bit still have plenty of wire-wrapping wire, terminals (including IC sockets etc.) and tools somewhere - but I never 'got on with' the system!
Kind Regards, John.
Surely then, that is not mechanically, and therefore not electrically, secure.
Have you looked at any of the devices in a CU recently (MCBs, RCDs, RCBOs, Main Switches etc.)?
Kind Regards, John.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
