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I bought a custom length of a 16/2 cable (two 16-gauge stranded wires, individually insulated). The two wires have identical colors and insulation; the only thing to tell them apart is that along one, there's printed specs of the wire, such as 600V and max temp.

I plan to use this wire for a ceiling light, and there's a chance that someone else will have to deal with this light if I move out and leave it installed.

Of course, it's possible for someone else to figure out how the lamp is wired either by looking at the lamp's own color-coded wiring or by tracing an individual wire from the power receptacle. But is there a good way to label the two wires of my cable, to make it clearer which is the hot?

Is there already a standard like, "the cable's side with the printed specs is the hot one"?

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    Might there be a ribbing on one side or a slight white stripe?
    – bib
    Jul 9, 2013 at 21:37
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    Polarized solid black, white or brown insulation -> Ribbed, grooved or striped side is neutral, smooth side is hot. Clear insulation lamp cord, silver conductor is neutral, copper conductor is hot.
    – Fiasco Labs
    Jul 9, 2013 at 22:13
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    @FiascoLabs walks like an answer, quacks like an answer...
    – HerrBag
    Jul 10, 2013 at 3:21
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    @HerrBag - You're right, converted it to a more complete answer below as I wanted to consult NEC. I dealt with this as a kid working on a hot chassis tube radio. Wire it right or get the bite. I even pulled the plug style fuse out of the panel and replaced the socket so I could have a polarized plug. Ahh, the freedom of rural rentals and the Boy's Book of Electricity. No more 110V tickle.
    – Fiasco Labs
    Jul 10, 2013 at 5:19
  • @FiascoLabs Ahh, the memories. My first large electronics project was a Heathkit SW Radio... had said tubes. (sorry for the hijack Philip)
    – HerrBag
    Jul 10, 2013 at 11:45

4 Answers 4

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NEC 2008 400.22(E & F) For lamp cord, the following conventions are followed:

Polarized solid black, white or brown insulation
Ribbed, grooved or striped side is grounded (neutral), smooth side is ungrounded (hot).

Clear insulation lamp cord
Silver conductor is grounded (neutral), copper conductor is ungrounded (hot).

Grounded (neutral) goes to the threaded shell of the lamp and is wired direct without break to the wide blade of a polarized 2 prong plug or in the case of a suspended lamp, to the grounded (neutral) white wire. Switching goes in the ungrounded (hot) side. You never want the thread shell to be hot (switch in off position in the neutral side with intact filament).

If the conductors are both the same color, the insulation is a single color and the printing is on one conductor's insulation only without rib (feel it with your fingers) or stripe, then that will be your continuous marker and grounded (neutral) indicator. The whole idea on zipcord is that you have some definite identifier as to what is grounded (neutral) to keep a continuous connection and wire properly to the lamp socket and wall plug.

National Electrical Code

ARTICLE 400 Flexible Cords and Cables

II. Construction Specifications

400.22 Grounded-Conductor Identification. One conductor of flexible cords that is intended to be used as a grounded circuit conductor shall have a continuous marker that readily distinguishes it from the other conductor or conductors. The identification shall consist of one of the methods indicated in 400.22(A) through (F).

(E) Tinned Conductors. One conductor having the individual strands tinned and the other conductor or conductors having the individual strands untinned for cords having insulation on the individual conductors integral with the jacket.

(F) Surface Marking. One or more ridges, grooves, or white stripes located on the exterior of the cord so as to identify one conductor for cords having insulation on the individual conductors integral with the jacket.

Note: National Electrical Code (NEC) is the US standard and quoting it defines this answer as being for US electrical power. If your country differs, feel free to post your own answer with your country or jurisdiction identified.

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  • In Philip's case, if the cord is not so obviously marked, a piece of black electrical tape on each end wouldn't go amiss (on the 'hot' (ungrounded) side).
    – HerrBag
    Jul 10, 2013 at 11:48
  • Hope you don't mind that I made your answer more prettier.
    – Tester101
    Jul 10, 2013 at 12:18
  • You did not say which countries this applies to. I can assure you this is not acceptable in a few countries.
    – Piotr Kula
    Jul 11, 2013 at 8:32
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    Citing NEC (National Electrical Code) pretty much defines it as US. Please add your own country specific answer.
    – Fiasco Labs
    Jul 12, 2013 at 2:17
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Within DC applications the cable with writing / line / strand is the negative.

Unfortunately in AC you should conform to colour standards in your country. But end of the day copper is copper. If you take the measures to label the wire up where ever you are connecting them (LIVE and NEGATIVE) or something that makes sense to anybody with the least technical knowledge - That is just as good as using the colour specification.

This is good enough ...

enter image description here

.. but since you making the effort its best to label up as standard.

enter image description here

Please note though

Obviously both would fail an electrical inspection and could put your home insurance into a void clause. In the event of a fire and inspection revealed uncertified installation could put you liable to service and damage costs. Just so you know now and don't go "nobody told me" later

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    I'd suggest using "electrical tape" of the proper color instead of the transparent tape. Electrical tape will have been approved for use in electrical boxes. In the United States, the neutral would get white tape and the line would get black (or some other non-green color)
    – Pigrew
    Jul 9, 2013 at 20:00
  • Its a good idea BUT it requires the OP to go and buy that coloured tape for single use only :) I suppose contractors use this tape in the US allot since you say its approved. In EU Countries that wont pass at all. And when I did my NVQ there was no mention of this either in the Home Building regulations (South Africa)- It might be omitted if it was a "temporary" cable ran on top of the plaster and not inside condiut or "fixed" in to the structure of the house. But I cant comment on that.
    – Piotr Kula
    Jul 9, 2013 at 20:03
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    The only color of electrical tape you need (in the U.S.) is black. You can't use a black wire that you put white tape on as a neutral. (Unless it is over a certain size) You can use black/red/blue/brown tape on a white wire and use it as a hot wire. (Commonly used for light switches)
    – Brad Gilbert
    Jul 11, 2013 at 5:34
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When wiring a grounded power cord to an appliance:
The SMOOTH (right) side is hot = connect to BLACK.
The GROOVED (left) side is neutral = connect to WHITE.
Sound correct?

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    I can't tell if you're asking or answering due to your inclusion of "Sound correct?"
    – Doresoom
    Feb 17, 2015 at 20:21
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I'm in Canada. Usually smooth side with writing is hot/black.

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