Electrical Wall Plug Wire ID & Connections

How to identify the hot & neutral wires by color, by ribbing on the zip cord or lamp cord, or by a white strip on the zip cord or lamp cord to be sure that your wall plug is wired properly.

Watch out: mis-wired electrical wall plugs or any other electrical wiring is dangerous, risking fire or shock or even death. Electrical wiring should be performed by a licensed, trained electrician and should comply with the National Electrical Code and local regulations. This article series describes how to choose, locate, and wire an electrical receptacle in a home.

Electrical Wire Identification at a wall plug or line cord

How do we know which wire in a line cord should be wired to the neutral or wide-space of a wall plug?

Why is knowing this detail important? Here we answer those questions. Photo: a add-on line cord switch used to turn a bedside lamp on and off should be wired so that the switch interrupts the hot wire, not the neutral wire.

Our page top illustration shows an un-grounded lamp cord wall plug connected to an electrical receptacle.

Older non-polarized wall plugs may have just two connecting spades, each the same size. Still you can easily identify which wire is the "hot" and which is the "neutral" in these line cords and wall plugs by observing any of several indicators we list below.

If the plug is not a polarized model, why should you care which wall plug is hot and which is neutral? After all, our building's electrical circuits are mostly 120VAC or 240VAC - where "AC" means "alternating current".

An electrical device will "work" regardless of which way the plug is inserted.

The answer is that some electrical devices are unsafe if polarity is reversed. Some of the hazards are subtle. Here are examples:

1. A lamp bulb socket,
   
   connected properly, hides its "live" terminal as a spot deep in the lamp base, but if wiring is reversed, the more-easily-touched bulb socket shell becomes live and can shock or kill someone.
2. It is important that a line cord switch,
   
   (shown above) often added to a lamp cord or other electrical device, is wired to interrupt the "hot" wire, not the "neutral" wire. Otherwise power remains live at the input to the device that you think is switched safely-off, increasing the potential shock or fire hazard.
3. On some appliances
   
   such as the igniter circuit of a gas cooktop or range, reversed polarity can cause an electric shock on touching the igniter or burner top even when the burner is "off" - see details in reader comments found
   
   at GAS COOKTOP or STOVE IGNITER REPAIR

Details about the hazards of reversed polarity are

at REVERSED POLARITY ELECTRICAL DEVICES / CIRCUITS

[Click to enlarge any image]

How to Identify the Hot and Neutral Wires in a Line Cord or "Zip Cord" Wire

Look for any of the following:

1. The ribbed side
   
   of the line cord indicates the neutral wire, the smooth side, the hot wire.
   
   If we are wiring a line cord plug, the ribbed wire would connect to the wider space or neutral space on the plug itself.
   
   If we are wiring a line cord switch such as shown in our photo, we take care that the switch interrupts the "hot" or smooth wire.
   
   Below we show a closeup of the ribbing along the neutral side or neutral wire of a line cord.

Below: white stripe indicates the neutral wire in this line cord.

2. A white stripe
   
   on one side of the line cord indicates the neutral wire, as shown above.
   

A near-transparent lamp cord used to operate a table lamp provides an example of identification of the neutral wire by noticing that the neutral wire is silver while the hot or "line" wire is copper colored.

3. If the line cord is transparent
   
   you may see that there is a silver wire (neutral) and a copper-colored wire (hot).

Really? Not always. As we illustrate below, some clear or translucent line cords will use two copper-colored wires, and others may use two silver-colored wires.

In that case you should expect one side of that line cord to bear ribs along the length of the neutral wire.

4. The wider spade of the wall plug
   
   marks which side of the plug is the "neutral" and should be inserted into the wider slot in the electrical receptacle (and cannot be inserted improperly in most modern receptacles).

5. A wall plug that includes a ground prong
   
   will force the plug to be inserted properly into the receptacle, as we illustrate below.

Shown earlier on this page (discussing use of a white stripe to mark the neutral wire), this particular grounded line-cord plug does not sport connector-spades of different widths; both are the same, but as we illustrate above, it is impossible to insert this plug incorrectly into the wall receptacle.

Below: we illustrate that not all electrical receptacles and line cord plugs require polarity.

6. Non-Polarized Wall Plugs & Receptacles
   
   include this 240VAC electrical outlet and line cord plug in use in an apartment in Venice, Italy.
   
   These cord wires and line cord plugs will not distinguish between the two wires, and both wires carry line voltage, typically at 120VAC, to provide 240VAC across the circuit.

...

Continue reading at ELECTRICAL OUTLET, HOW TO ADD & WIRE - home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Electrical Receptacle Wiring Articles

• ELECTRICAL OUTLET, HOW TO ADD & WIRE - home
• ELECTRICAL WALL PLUG WIRING ID & CONNECTIONS
• SPLICING ELECTRICAL WIRES
• STRIPPING ELECTRICAL WIRES

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