Connecting Three 12 Gauge Wires

Question

When I purchased our house the previous owners recently installed electric baseboard heaters in rooms A, B and C. I did not want to keep these but needed more outlets so I had swapped the breaker at the panel so I could run 110 volt instead of 220 volt.

Originally the feed line (from the panel) ran from the panel to the heater in room A. It was then spliced directly on the unit and a line ran to rooms B and C. After removing the baseboard units I ran the feed line to the outlet in room A. I ran a line from the outlet to a junction box, then spliced in the lines that go to rooms B and C.

Last night, one of the outlets that is connected at the junction box stopped working, then started working but received very little power. I immediately cut the power to the line at the panel. The other two outlets were working properly. It was really late so I didn't dig into the problem too much but did verify that the connections at the outlet were tight. I am assuming the problem is somewhere in the junction box.

Since the lines were originally running 220 they used some 12/2 wire. When I put in the junction box I had a hard time getting a good twist on the wires before putting on a wire nut and was worried that at some point they would come loose. I am pretty sure I used the red wire nuts which I think should be the correct ones, right? I don't think wrapped them in electrical tape but should I? Any tips on how I can keep this from happening again?

Answer 1

You have to use the right size wire nuts, and you have to put them on correctly. If you recall correctly, you have the right size, so you may not have put it on firmly enough. Another common problem is not having all the wires at the same length, so that one is not as well connected. Only when connecting stranded and solid should the stranded be just a bit longer/further into the nut than the solid wire(s).

You may find it easier to use a nut with "Wings" that make it easier to twist forcefully.

Do NOT pre-twist the wires. The wires, stripped to proper length (per instructions of the wire connector - look on the box) and aligned with each other are twisted BY the wirenut as it's installed (some instructions may say "pretwist optional" but in point of fact I find that it works best if the twisting is all done by the wirenut.)

Tape does nothing to prevent or solve a poor connection.

Answer 2

Assuming that you are talking about solid copper conductors, you should pre-twist the wires together before putting on the wire nut. A red wire nut is the correct size for the type of wire and number of conductors you are asking about.

Strip approximately 3/4" - 1" of insulation from each wire, and align the wires together and firmly hold it beneath the stripped portion. In your other hand take a pair of lineman's pliers and grip the end of the wires and slowly twist clockwise until the stripped part of the wires are twisted together; being careful to only twist the stripped wire. It is better to hold the pliers parallel to the wire and grip it right near the end instead of holding them perpendicular. Using the lineman's pliers, snip of the very end of the twisted wires to even out the ends of the wires, and then screw on the wire nut.

If it is done correctly, there is not a need to wrap tape over the wire nut. I generally only do that if the wires are exposed to the elements. There is nothing wrong with doing that if you want to take the belt-and-suspenders approach.

If you don't twist the wires prior to putting on the wire nut, then there is a higher chance of the wires pulling apart and causing a bad connection. You are fortunate that the connection just caused a voltage issue. A bad connection could short out and hopefully cause the circuit breaker to shut off the circuit. A worst case scenario, is that the wires could arc, and potentially burn the building down.

Answer 3

Pre-twisting is a good practice to assure the wires are "ready" for the wire nut. The use of tape is to prevent the nut from unscrewing or vibrating loose. The tape is wrapped in the same clockwise manner as the nut. You start by wrapping the wires, wrapping around the nut and then back down to the wire bundle. Of course the tape is being pulled very tight throughout the process. This makes it very difficult for the wire nut to ever come loose.