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Electrical wiring colour codes:
This article describes the electrical wiring color code conventions for 120V or 240V AC circuit wiring in buildings in Canada, the U.S., the U.K. and the I.E.C. Quoting from authoritative codes & standards for each region we provide a table summarizing the current and prior wiring color code conventions used by electricians in building wiring.
For each color code table we include authority citations and links to sources of codes, books, standards and wiring guidelines. We point out with photo-examples that while wire color code theory is nice and all that, in the real world of working on existing buildings, wires are not always reliably color-coded and colors may in fact be impossible to discern. Some of the wire color images here were adapted from data provided by the Malta Resources Authority's excellent document on Harmonisation of Wiring Colour Codes - cited below.
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But as we will illustrate below, on some older buildings spotting any color at all in the wiring insulation or jacket can be difficult or even impossible. Here are links to the electrical wiring color code conventions used by various countries.
On older wiring such as this rubber and fabric-jacketed household wiring from a U.S. home, figuring out what the heck the wire colors are can itself be a challenge.
Look closely at the fabric covering of the two wiring strands in our photo.
The upper wire is the "white" or neutral wire.
The lower wire, whose fabric insulation is black with red and white tracer threads is the "black" or hot wire.
But sometimes there is no clear color distinction between the two wires: you'll need to trace the wiring and use a DMM or VOM to figure out which wire is "hot" and which is neutral or ground.
This knob-and-tube electrical wiring photo has useful information for the electrician or building inspector.
First we can see that if we're in luck, the fabric portion of the wiring insulation may be intact and may clearly show that one conductor is white (neutral) and the other black (hot). With age the white insulation may have become tan or even brownish in color.
Second I'm a bit nervous about how that white wire is stripped back and is in contact with the hot black wire (arrow).
Finally, of course there is no protective ground on this circuit - we've got just two wires with which to contend.
This wiring shown above - well don't even think about figuring this out by color codes. Someone has just grabbed a piece of yellow wire and a blue wire, left an open splice, and jury-rigged something (not shown in our photo).
But when you see obviously amateur electrical--wiring like this it's a red flag to watch out, asking "what else did this fellow wire in this building?"
Continue reading at ELECTRICAL WIRING BOOKS or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
(Mar 12, 2014) Keith E. Davis said:
In the U.S. UL (the Underwriter's Laboratory) has published wiring color acronyms and abbreviations. We have included the standard wiring color code abbreviations along witht the full color name in our tables of wire color standards in the article above. Thanks for asking.
Also see UL Standard 83 - Thermoplastic-Insulated Wires and Cables
Question: ok to reverse red and black wires?
(July 18, 2014) Eric said:
Eric without knowing what's being wired all we can say is ... Yes it might.
Generally in house wiring the red wire is a second 120V circuit on a different "phase" such that it can either provide 120V to a device or if wired along with the black wire to two terminals on some devices (such as a 240V motor) the circuit will be provided with 240V. In a 240V circuit generally which terminal gets the red and which the black won't matter.
Question: wiring an electric 600V water heater in Canada
(Sept 11, 2014) Bob said:
For Canada, 600V unit, water heater, does the ground wire have to be green/yellow or just green?
I'm referring to internal wiring, sorry.
Bob Here's a quick summary of colour conventions for the protective ground wire:
The protective ground wire (listed as green-yellow in CURRENT codes & standards) is green with yellow stripe in the UK and IEC.
In the U.S. the ground wire might be bare, or green-yellow (preferred) or green (alternative)
In Canada the ground wire (Protective Ground or labelled PG) can be green-yellow OR green.
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