How to cover exposed copper ?

I use small bore Teflon tubing that is available from many vendors. Unlike PVC, it doesn't shrink back when you solder near the ends. If that is not an issue, then just strip some insulation from a larger gauge wire and use that.

John

OK. Thank you!

I just re-read your question. Based on this sentence:

I need the copper connection to be intact and I don't want anyone to touch the exposed live copper.

Click to expand...

is it for mains wiring? If so, you need a box or something to meet code for in-line splices. My comment was related to low-voltage only, like on a circuit board.

3M black electrical tape is used for a lot of things. I use it too, but don't like the way it tends to peel off and leave stick goo with age. 3M also makes a self-fusing rubber tape called, Temflex Rubber Splicing Tape #2155. When properly applied, it fuses to itself and gives a more permanent repair. It is quite thick and does not feel sticky like tape, but don't let that fool you. It is virtually impossible to unwrap after it has been on for a few hours.

John

Exactly what type of wire was this: building wire or cable (usually found inside walls), or an appliance cord, or something else?

Also, aside from mains building wire splices needing to be in a proper enclosure, you didn't specify how you "joined" the wires. There are many ways to do so, both safe and unsafe. Please be specific. For example, merely twisting solid-core wire together then taping it will often give a poor (high-resistance) connection, either initially or at some future time after the copper surfaces oxidize sufficiently. Then the connection may overheat and start a fire, or may damage a connected appliance due to excessive voltage drop.

As JP said use a sealed joint box with screw terminals.

>> is it for mains wiring?
No, this is low voltage wire in a circuit board. This is ground wire for a switch input to my embedded target board.

>> strip some insulation from a larger gauge wire and use that.
How would I cover exposed copper with this insulation ?

>> how you "joined" the wires
I intertwined the wires with my fingers.

>> For example, merely twisting solid-core wire together then taping it will often give a poor (high-resistance) connection, either initially or at some future time after the copper surfaces oxidize sufficiently. Then the connection may overheat and start a fire, or may damage a connected appliance due to excessive voltage drop.

My wire is general purpose circuit board wire. Is it solid-core wire ? If taping exposed copper is unsafe, then, what's a safe solution ?

Merely twisting together any wire is generally considered an unreliable connection, especially when dealing with mains AC power. If this connection will be enclosed in some way that protects it from fingers of the curious or inept, or other kinds of accidental contact, then simply soldering the twisted connection and insulating it with electrical tape (the black kind; your #4 above) may be sufficient. If the exposed copper length is short enough, another option is a wire nut (twist-on pressure connector), which should not require any additional insulation as long as no copper is easily accessible beyond the base of the connector. Most people on these forums would probably prefer to untwist the connection, slide an appropriately-sized section of heat-shrinkable tubing over one of the wires, re-twist them, solder them, then slide the heat shrink over the splice and shrink it. There are other methods that will work safely too.

Option #2, wire nut:


Wire nut steps:


Wire nut properly installed:


Option #3, soldering.
Twist solid-core wire:


Or twist stranded wire, and soldered:

Be sure to crimp and/or trim the ends of the wire tightly against the splice, so that they do not poke through the tape or tubing that you use to insulate the connection.

Heat shrinkable tubing, in place:


Heat shrinkable tubing, shrunk:

Please note that heat shrinkable tubing does not usually shrink much in length, only diameter; the tubing is much shorter in the second image because I got these images from different sites.