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I know this question is way, way below the norm for this type of place, but I just want a straight answer and not something that I have to try to glean from other places answering a different question.

I'm replacing a light fitting in my house, except in the new one the junction box is basically affixed to the fitting itself, and I needed some longer wires to be able to fit it, the problem is the only type of wire I have is a spool of earth wire, and not one for live or neutral. I ran to Wickes to try to get some other types of wire but they only had earth too, but they did have electrical tape in red and black.

I realise that the wires are used for different purposes, however, is there any actual difference in the physical wires themselves? eg, would a section of piece of earth wire, wrapped in red electrical tape, work instead of the live wire? I assume they're all just copper wire, and the colour is just for identification purposes, but I just wanted a straight answer to the question from someone that knows

Thanks

  • Can you post photos of the inside of the box? – ThreePhaseEel Jul 14 at 22:28
  • Also, can you get some T&E or the likes that you can shuck for this purpose? – ThreePhaseEel Jul 14 at 22:28
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There are two separate issues here:

Bare Ground vs. Anything Else

A bare ground of a particular size is, nominally, no different from an insulated wire of the same size. However, wrapping a length of wire with electrical tape does not provide the same level of protection as manufactured insulation, and is not considered a reliable substitute. Among the problems:

  • If you miss a spot when wrapping, you have a real safety problem.
  • The ends (and there may be many "ends" as you wrap a long wire) of sections of electrical tape are more prone to catch on screws, other wires, parts of junction boxes, etc. than manufactured insulation
  • The thermal and/or electrical properties of electrical tape may be sufficiently different from manufactured insulation to cause a problem

Electrical tape is great for:

  • Patching up a nick in the insulation of a wire (ideal is to replace the wire, but that is not always so easy)
  • Wrapping around screws on a device (receptacle or switch) to prevent contact with ground wires
  • Marking wires for identification (within certain limits)

but not as a replacement for insulation on a length of wire.

Note that ground is the only wire that can be bare. That is because it is also, depending on other factors, often attached to metal boxes & conduit or to appliance frame/casing, all of which are (effectively) "bare metal". All other wires, including neutral wires that are nominally "same as ground", are insulated everywhere.

Changing Colors of Wire

The general issue of changing the color of a wire is an interesting one. The actual colors (except for ground = bare, green or green/yellow) vary significantly by country/region. Using the US as an example (I assume you are in the UK based on reference to Wickes), the normal colors are:

  • Neutral = white or gray
  • Hot = black, red, blue or any other color except green, green/yellow, white or gray

Within each category, wires can be marked using tape on the ends. For example, you can mark black wires yellow by putting a piece of yellow tape on each end for identification. However, you can't put white tape on black wire (to change hot to neutral) or red tape on white wire (to change neutral to hot). There are some exceptions with cables (e.g., to mark a switched hot), but this is a nearly universal rule.

The end result for your situation is:

  • Can't turn a bare wire into hot or neutral by wrapping with tape
  • Can't turn a green or green/yellow wire into hot or neutral by marking the ends with tape

You might be able to turn a green or green/yellow wire (i.e., insulated but wrong color) into hot or neutral by wrapping the entire length with an appropriate color of tape (i.e., does not have the "miss a spot" or "maybe not insulated well enough" problems). I wouldn't recommend it, but a UK code guru could give you the answer to that option.

  • A lot of "electrical" tape is suitable for marking/colour coding only, and it has not been tested to comply with the requirements for insulation tape. Red and black are also no longer appropriate colours and all new work should be brown (L) or blue (N). Stripping the individual wires out of some flex or cable is the easiest way of getting insulated coloured wires, although they can be bought on reels as 'singles' for conduit wiring. – Owain Jul 14 at 16:22
  • I thought there may be some difference in terms of resistance or insulation, to a layperson I assumed the internal wire is just copper wiring, and there'd be no difference, aside from helping to identify the difference. I've not ended up doing this anyway, I was just annoyed that I'd already been out twice, to pick up the lights and again to find a wire, and all the shops are shut now to get the proper stuff, so I wondered if it would be fine – Andrew Morris Jul 14 at 16:39
  • @Owain You're probably right about the colors for UK, but keep in mind that colors vary a lot around the world. Agree on "Strip the individual wires out of some flex or cable" - that is routine in the US with Romex. – manassehkatz-Reinstate Monica Jul 14 at 21:09
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I am surprised that Wickes did not have any lighting cable in stock (either 1mm^2 or 1.5mm^2) to enable doing the job properly.

Using earth cable is not advised even if it is the same copper diameter as if the tape falls off (which it can over time) would be very dangerous for any person working on it in the future.

Get the correct cable and do the job properly.

  • Yea they only had earth cable, even asked if they should have any but there didn't even seem to be place for it. What I've described above certainly isn't meant to be a suitable solution, I was just wondering if there was any actual difference, because I'd already been out twice, once to buy the lights, and again to try to get the wire, and it being a sunday everywhere will have shut by now to get the proper stuff – Andrew Morris Jul 14 at 16:36

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