40
\$\begingroup\$

Seemingly obvious question, but. There are electrical supply companies that sell insulation tape in boxes of 12 or 24 units. Seems that there's quite a demand for the stuff.

No commercial product I've ever seen uses insulation tape. They use connectors, solder, heat shrink, etc. I don't think that electrical code allows for wiring up a house by twisting the wire cores together and taping them. You're not supposed to extend a lampshade flex by twisting on another length and covering the joint with tape.

I've used loads of the stuff for setting out road pin levels and concrete slabs. It's very good for that. I once saw a video of a 10KV splice being made and they used lots of tape for it, but that didn't seem to be the stuff from the DIY shop.

I'm curious as to what the approved use of insulation tape is? And if there isn't one, why isn't it banned for electrical work?

STOP THE PRESS...

I've just put up a fluorescent light fitting. It's from Wickes, a UK DIY store. This is from the instructions:-

Tape example

This is the first example I've ever seen of insulation tape being mentioned in a retail device. I now know what it's for...

\$\endgroup\$
  • 6
    \$\begingroup\$ Like coat hangers and paper clips, it has a main purpose but can be used for many reasons. It is made with PVC, so it has limits as to what it can do. \$\endgroup\$ – Sparky256 Jul 5 '16 at 0:13
  • 4
    \$\begingroup\$ @JJOz: This is a use electrical insulation tape is explicitely not designed for. \$\endgroup\$ – Ariser Jul 5 '16 at 7:36
  • 26
    \$\begingroup\$ It's for when you want to make a gummy mess, but not immediately \$\endgroup\$ – Scott Seidman Jul 5 '16 at 12:59
  • 3
    \$\begingroup\$ @Lamar, are you sure you're not speaking about gaffer tape? \$\endgroup\$ – Henning Makholm Jul 5 '16 at 13:14
  • 3
    \$\begingroup\$ @lamar if they are using electrical tape for that, hit them. That's what gaff tape is for. None of the sticky leftover residue! \$\endgroup\$ – Passerby Jul 5 '16 at 15:51
39
\$\begingroup\$

Four ways electricians use black vinyl 'electrical tape':

Wrap around an outlet or switch, to cover the live electrical terminals, before stuffing the outlet or switch into its electrical box. This prevents surprises in later opening the (possibly live) box, and protects against contact with the bare ground wire in that box. Other 'live' metal (like big splices) gets more elaborate treatment, but taped twisted-wire splices are sometimes encountered in elderly wiring.

Repair loose insulation (old cloth especially) when reworking an old device. Sometimes even covering a nicked or scorched bit of damaged insulation, if replacement is not feasible.

Identifying different wiring use: if you run a black/white/green cable to a distant switch, the white wire is not 'neutral', but 'switched hot', so is given a wrap of black tape to mark this variant function. Green (or bare) cannot be given a different use, it can ONLY be ground.

Pulling wires, like in a conduit, with a steel 'fish tape'. You twist the wire into the fish tape's end, then cover the edges of the assembly with vinyl tape so it doesn't catch. At the end of a big job, there's a lot of short twists of wire with black tape, and maybe pulling lube, in the discard bin.

\$\endgroup\$
  • 5
    \$\begingroup\$ I use it (right or wrong) to tape then end of the wire nut. Stick two wires in a wire nut and twist in the normal fashion, then a layer of electrical tape around the bottom before shoving them back into the wall. To my mind it only helps keep the wire nut in place, even though it shouldn't need it. \$\endgroup\$ – coteyr Jul 5 '16 at 21:50
28
\$\begingroup\$

The primary purpose of electrical tape is to insulate wires after they have been spliced in an approved manner. The US National Electrical Code permits splices to be made in various ways:

110.13(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. Soldered splices shall first be spliced or joined so as to be mechanically and electrically secure without solder and then be soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an identified insulating device.

So if you really want to, you can wire your house by twisting the wires together soldering them and taping them with electrical tape. I have actually seen this in old houses. But nowadays you will find it easier, quicker, and cheaper to use readily-available wire nuts. (A wire nut would be a combined "splicing device" and "insulating device".)

Electrical tape is still widely used when splicing larger conductors which are too big for wire nuts. Often splice bolts are used. These are bare metal clamps which bite down on both wires. Once the bolt is installed it is wrapped in multiple layers of tape. You can often see these splices at the service entrance where the wires from the street join the cable leading down to the meter.

The reason electrical tape may not be used to splice a lamp cord is that splicing of such cords is not allowed at all (NEC 400.9).

\$\endgroup\$
  • 3
    \$\begingroup\$ Great answer. Can add that for the large bolt-type splices, we first wrapped the splice in a thicker, foam-like tape before covering the lot thoroughly in electrical tape. The foam built-up the shallow areas and gave extra protection to the sharp corners. \$\endgroup\$ – JS. Jul 5 '16 at 18:23
  • 4
    \$\begingroup\$ Electrical tape is also used on top of wire nuts to prevent other wires intruding into the nut, and to help ensure that the nut doesn't become loosened with time. \$\endgroup\$ – BrianFreud Jul 5 '16 at 18:59
  • 1
    \$\begingroup\$ I've also heard of multiple wires being pre-wrapped to hold them together for wire-nutting. \$\endgroup\$ – rrauenza Jul 5 '16 at 20:48
  • \$\begingroup\$ This is what I saw on the 10kV splice. They needed a socket set and wrench to do up the splice bolts. \$\endgroup\$ – Paul Uszak Jul 9 '16 at 0:10
13
\$\begingroup\$

In addition to the excellent answer from Whit3rd, some other uses for vinyl electrical tape are:

Insulating low-voltage splices and connections.

Securing wire or cable to a stationary or supporting beam or post or cable.

One of my hobbies is doing professional Pyro and Fireworks. We use e-tape by the dozens and dozens of rolls in a single show. In addition to all of the other uses previously mentioned, we'll use tape to secure large Roman candles to their racks, tape bundles of small cakes together so as to make them more stable and not able to tip over, dozens of other similar uses.

For What It's Worth, early electrical tape was made of cloth and often referred to as "Friction Tape". Most houses and many commercial buildings were wired with twisted copper connections which were then insulated with friction tape. Sometimes, those twisted connections were soldered before being taped up - but not always.

\$\endgroup\$
  • 2
    \$\begingroup\$ By my understanding, the term "friction" didn't refer to electrical resistance, but to mechanical friction, since one of the uses of friction tape was to improve traction or grip on various surfaces. I'm not sure whether tape designed for electrical use acquire the other use and name, or whether electricians found that friction tape which was useful for other purposes also suited their needs. \$\endgroup\$ – supercat Jul 5 '16 at 17:15
  • 2
    \$\begingroup\$ The problem with friction tape is that it dries out and becomes fragile with age - I've seen old friction tape literally turn to dust when touched. It also can easily lead to fires, with the cloth catching the spark from a short. \$\endgroup\$ – BrianFreud Jul 5 '16 at 18:58
3
\$\begingroup\$

I would like to offer a different take on this, in particular aimed at readers in countries which follow IEC derived wiring regulations (most places other than North America) as opposed to US/Canadian National Elctrical Code (NEC) https://en.wikipedia.org/wiki/Electrical_code

Electrical insulation tape is actually an oxymoron. It generally does not have an insulation rating in V, kV, etc, therefore it cannot be guaranteed to provide insulation for any given voltage (other than maybe for extra low voltage systems <55VAC/120VDC). Also PVC has a relatively low melting point of 60 deg C and the tape is quite thin so liable to mechanical damage. Over time the adhesive gets sticky, migrates and loses adhesion, so there's no guarantee it wont slowly peel off. How many turns are required to limit the risk from the above factors?? This is never specified.

There is a key difference between countries with follow NEC where wire nuts are allowed and those using IEC derived wiring regulations where they are not. In IEC countries, flexible conductorswires are usually fixed in screw/sprung terminals (or occasionally crimp terminals) and are always terminated so the insulation is covered by the terminal/connector shroud so there is no bare conductor exposed. All new electrical panels and enclosure use IP21 'touch proof' terminals and connectors. Therefore there should be no need to use insulation tape in formal electrical engineering if best practise is followed.

For identification of cables coloured sleeves and alphanumeric markers are available.

For insulation in proximity to high temperature lamps and heating elements woven fibre glass can be used.

For application such as covering soldered joints in electronics work, a better solution is to use sleeving such as heat shrink sleeving.

For protection outdoors denzo tape or similar can be used.

\$\endgroup\$
  • 1
    \$\begingroup\$ While I am sure these are all fine and likely even better ways to make electrical connections, the central premise of the answer, that "electrical insulating tape is actually an oxymoron" is false. Electrical tape does in fact have an insulation rating, usually 600 volts. It is an electrical insulation device with regulatory approval as indicated by the Underwriters Laboratories seal on the roll I have right here. Thus the intended purpose of electrical tape is to insulate wires, whether or not such use is approved in IEC countries. \$\endgroup\$ – David42 Jul 6 '16 at 22:24
  • \$\begingroup\$ Also, how would you insulate a split bolt? They don't lend themselves well to heatshrink type sleeving (too knobby), and don't exactly come with insulation by default. \$\endgroup\$ – ThreePhaseEel Jul 6 '16 at 22:49
  • 1
    \$\begingroup\$ Insulating a split bolt is usually done with rubber 'fusion tape' which adds bulk, with maybe an overall cover of vinyl tape. There is also a 'liquid tape' product sometimes used. Simple vinyl tape wrap would be an unusual way to do it. \$\endgroup\$ – Whit3rd Jul 7 '16 at 5:36
  • \$\begingroup\$ @Whit3rd -- I was asking SolarBrian because I'm not sure what he'd do with those things :) I know what's done in the US (aka what you describe) \$\endgroup\$ – ThreePhaseEel Jul 7 '16 at 11:42
  • \$\begingroup\$ It appears that electrical tape is a thing under the IEC too: webstore.iec.ch/preview/info_iec60454-2%7Bed3.0%7Den.pdf \$\endgroup\$ – David42 Jul 7 '16 at 13:16
0
\$\begingroup\$

It's primary use now is to cover up the flashing clock on your DVD player, cable box or stove after the power fails and you are too lazy to reset it...

Seriously though, it's kind of like the "Duck Tape" of the electrical world; you can't describe the potential use for it until that moment when you need it, then you are cursing yourself for not having bought enough.

And no, the term is not "Duct" tape, that's a common misconception that came about AFTER people in the HVAC industry started using it for air duct sealing. Technically, it's horrible for that because it doesn't last with all the temperature changes. The official kind of tape to use for that is foil tape.

\$\endgroup\$
  • \$\begingroup\$ "duck/duct tape" isn't a formally defined term at all, just a nickname, so both are okay in my books. Also, there are heat-resistant varieties that can be used for HVAC work. \$\endgroup\$ – FlashCactus Jul 12 '16 at 10:16
0
\$\begingroup\$

It's just an established name, like the "duck tape" (which presumably is neither made out of ducks, not made for taping ducks) or "panzer tape" (which may or may not be used to fix tanks) or ... - the meaning of a thing does not always get reflected in the name, perfectly.

You can use it for lots of things (except insulating relevant amounts of voltage), and it is very useful for insulating things like 5V/3.3V circuits.

\$\endgroup\$
  • 5
    \$\begingroup\$ duck tape is called duck tape because it is made from Cotton duck fabric. Why cotton duck ? its dutch "doek = "linen canvas" \$\endgroup\$ – JonRB Jul 7 '16 at 9:41
  • 1
    \$\begingroup\$ There's also a Duck Tape company. \$\endgroup\$ – user2943160 Jul 7 '16 at 13:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.