Can I use electrical tape for making a splice? If so, how?

Question

What is the approved method for creating an electrical splice to 14 gauge wire intented to carry 110V, 10 amps (standard residential power) in USA? What does code say about tape-splices? The splice will be in an electrical junction box, located in a hallway, and a split bolt will not be used.

Answer 1

NO! But, I will answer the following question first, as it leads us to an answer about the use of tape:

What is the approved method for creating an electrical splice to 14 gauge wire intended to carry 110V, 10 amps (standard residential power) in USA?

You have to use a "splicing device identified for the use" according to NEC 110.14(B) Splices. Most electricians would either use a wire nut or a WAGO 221 clamp. Both are UL listed and both will last decades without the need for electrical tape.

The original question stated "a split bolt will not be used", which indicates to me that the intention was to use a pure "tape-splice" without any UL listed splicing devices. UL approved electrical tape by itself is just an insulator, but not an approved splicing device.

Based on this, the answer to:

Can I use electrical tape for making a splice?

is: No, not legally in the US! - Or as a comment by GManNickG stated: "You don't use electrical tape for making a splice; it's almost certainly illegal, it's terrible workmanship, and it's harder to get right than other actual splices."

The reason for requiring a splicing device, is that additional to insulation, the wires need to be pushed together with pressure and stay pushed together. As tape weakens over time and due to heat, the wires will start to separate. A loose connection will lead to heat and possibly arcing, presenting a fire risk.

Electrical tape cannot provide this kind of pressure over the lifetime of the connection, which could be decades, whereas wire nuts (mostly USA), WAGO clamps (mostly Europe) and screw terminals (mostly Australia) do accomplish this. In countries where taped splices are predominantly used (such as the Philippines) many problems can be observed with this method.

Answer 2

Based on comments above tape cannot be used (alone) for creating a splice. As Tester101 pointed out if the splice was soldered or crimped or joined with some (UL approved) device, then tape may be used for insulating the splice.

With regard to splices made with connectors, the method below could be used for insulating the connector (of specifically, a pigtail type of splice).

There are at least three kinds of electrical tape that I am aware of: vinyl, rubber, and mastic. For this purpose I would use rubber and vinyl, (reserving mastic for split bolt or similar connectors). I'm not sure if you must use rubber, but it will provide more thickness and (I believe) better moisture protection than vinyl. The tape used should be UL listed and approved for insulating splices. Generally speaking, the insulating tape should be 1.5 times thicker than the conductor's original insulation (source- http://ecmweb.com/content/electrical-taping-skills-lost-art).

If the connector has an exposed metal surface then I would start by wrapping it with (at least) one layer of mastic tape. Rubber tape will be used next (supposing the connector was not insulated), then vinyl tape on top of the rubber tape. Rubber and vinyl tape will be wrapped around the splice using a process called half lapping. Half lapping tape means to cover 1/2 of the tape every time you go around it. Start by stretching the rubber tape until it almost snaps and tear or cut off the end. Begin wrapping about 1.5 inches below the connector or stripped part of the wires. Keep tension on the tape (stretching it until it is ready to snap) while wrapping. When you get to the end of the splice, continue to wrap the tape upon itself two more times (wrapping the tape around itself), then fold the tape down, and wrap over it, continuing the half lap process back to where you started; cover the area where taping began and then (changing direction) continue wrapping back toward the end of the splice. Repeat the wrapping process, but this time fold the tape over the opposite direction (and wrap back down to where the tape was started). Cut the rubber tape and get the vinyl tape ready.

Rubber tape should be wrapped over the splice at least 4 times: up = 1 wrap, fold, down = 2 wraps, up = 3, and back down = 4. Then vinyl tape should be wrapped over that (again, using half laps four times).

Start by exposing a few inches of the vinyl tape. Pull it so that it stretched a little (about 30% length). Cut the end off and begin wrapping just below the rubber tape. Use the same half-lapping method, keeping tension on the tape so that it is stretching (slightly) while wrapping. When you are done the diameter of the splice should be thick enough (about 10 mm thick around the two wires); but if not, you should wrap it once more with vinyl tape (up and down) to be sure.