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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.

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    Why would you splice instead of using an approved connector like a wire nut or push-in connector? I don't think a tape-splice would change the box-fill calculation, so I'm curious why you would use one. – Johnny May 16 '16 at 18:23
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    NEC 2014 110.14(B) Splices. Conductors shall be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Not sure tape splices are allowed anymore. However, the method described in your answer would be acceptable for insulating brazed, welded, soldered or crimped splices. – Tester101 May 16 '16 at 18:33
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    @BenWelborn just having the UL mark, doesn't mean it's approved for whatever you want to use it for. It means that it meets the specific requirements of a product that can be used as described by the UL section it is listed for. – Tester101 May 16 '16 at 19:11
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    UL White Book INSULATING TAPE (OANZ) Use This category covers rubber insulating tape for insulating joints and splices in electrical conductors where an outer covering of protective material, such as friction tape, is intended to be applied over the insulating tape. This category also covers thermoplastic tape intended for use as the sole insulation and covering of joints and splices in electrical conductors. This tape is suitable as electrical insulation at not more than 600 V and at temperatures not exceeding 80°C (176°F). – Tester101 May 16 '16 at 19:22
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    Tape is listed for insulating splices, not as a "splicing device". – Tester101 May 16 '16 at 19:23
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Edit- 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.

  • Doesn't seem worth the trouble .... – brhans May 16 '16 at 18:58
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    In the old days there was a requirement for 7 turns on a T tap, and a y type if a western union type splice it was a minimum of 4 on each wire for a total of 8 turns. I don't even know any body that teaches this any more. – Ed Beal May 16 '16 at 19:03
  • "the insulating tape should be 1.5 times thicker than the conductor"; do you mean the conductors' original insulation? – Jimmy Fix-it May 18 '16 at 5:47
  • @JimmyFix-it yes, thank you for noticing that. I made the correction. – Ben Welborn May 18 '16 at 12:36
  • I feel like this answer does more harm in good. The quick answer is "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." Some homeowner is going to see this and think it's fine to splice their wires with just some tape (probably buried, of course). Also, the question asks "How do I use electrical tape for making a splice?", while this answer is entirely about insulating a splice. It doesn't actually answer the question. – GManNickG May 18 '16 at 21:37

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