Quote Originally Posted by rgsparber View Post
I now see that I caused some confusion when I talked about "power cables". I have changed the title to "extension cords".

I'm not sure what you mean by "low voltage" and "low current" but my intent was to splice extension cords used in 120V circuits which carry under 10 amps.

I completely agree about the dangers of tinning wires before crimping or using screw clamps.

I had not thought about faults causing the solder to melt before the breaker trips. It does surprise me given the large resistance of the extension cord and the low resistance of the splice. Wouldn't the extension cord start to burn first?

I have never been able to apply heat to a Western Union splice and have it detach unless it is also under a lot of tension. In this case, the wire usually breaks next to the splice. Now, if it was a simple lap joint, it is not to be trusted.

Rick

BY the way, if anyone is looking for the NASA link on workmanship, here it is:
https://nepp.nasa.gov/files/27631/NSTD87394A.pdf
Soldered splices start at page 68.

Other standards can be found here: https://nepp.nasa.gov/index.cfm/5511
I believe Jon posted a link to NASA standards in one file a while back. HERE IS ONE:https://archive.org/details/nasa-wor...ge/n3/mode/2up


What I meant regarding low voltage and low current are battery powered type projects, such as an Arduino circuit. Mains circuits have the capacity to supply hundreds, even thousands of amps very quickly during a short circuit. That's why circuit breakers are rated for 10,000A short circuit capacity for home panels and much higher for industrial applications and building distribution panels. Also, conductors experience tremendous forces during a short-circuits due to generated magnetic forces and capable of whipping cables around, hence the requirements for fastening cables at regular intervals and at junction boxes. Solder is much less conductive than copper (by a factor of ~10 if I recall correctly) and in an event of an overload, the temperature of the solder will rise very quickly and can melt. By the way, eutectic solder is used in thermal circuit breaker and melts during an overload, which then allows a ratchet mechanism to rotate and trip the breaker.

I am not saying that your method will result in a the wires separating, but I would not trust it from burning down my house.
What is applicable here is not NASA, but NEC code. I am not sure that NEC code allows electrical splices outside of a junction box or without an approved splice device that completely encloses the splice and mechanically secures the cables. There are products like these below that can be used for solid wire in certain situations (such as fished wire in existing building): https://www.homedepot.com/p/NSi-Indu...MS-3/307358485. Perhaps some electricians can shed some light on the NEC code requirements. I worked with industrial equipment twisting wire and soldering to splice is a no no.

While the western union splice is accepted by NASA, it is used with solid wires. Twisted soldered stranded wires fail quicker than untwisted wires. If you dig in the NASA case files and others, you'll find examples.

By the way, I love your posts and ideas you publish and always learn something new.