# US household wiring **URL:** \ **Category:** Factual Questions\ **Created:** [May 19, 2017, 8:18pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030 "2017-05-19T20:18:24Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [May 19, 2017, 8:18pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/1 "2017-05-19T20:18:24Z")
In electronics, black wire usually indicates ground. In house wiring, why is white neutral and the black wire is hot? ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [May 19, 2017, 8:34pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/2 "2017-05-19T20:34:13Z")
Technically, the National Electrical Code only specifies white or gray for the neutral, and bare or green for the safety ground. No other colors are mandated. But in practice, black is used for the normal hot wire, red as the other hot in a 240V circuit, and blue or yellow for other switched hots (ceiling fans, etc.). But why those specific colors were chosen? I don’t know, would be interested in that answer. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [May 19, 2017, 8:37pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/3 "2017-05-19T20:37:33Z")
Back in the 1920s, residential electrical wire used a cotton cloth braid for insulation. The cotton could either be left its natural color, which was grayish, or it could be bleached white. Either color could be used for the neutral. The cheapest and easiest dyes to use back then were either black or red, so those became the standard colors for the hot wires. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [May 19, 2017, 8:40pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/4 "2017-05-19T20:40:07Z")
Any solid color except white, green, and gray could be a hot wire. I don’t know why black is the most common color for hot wires, the codes go back nearly 100 years. Possibly black was the readily available insulation color when the code was first adopted. ---
**Author:** ![igor\_frankensteen](https://avatars.discourse-cdn.com/v4/letter/i/839c29/32.png) [@igor\_frankensteen](https://boards.straightdope.com/u/igor_frankensteen)\ **Post date:** [May 20, 2017, 7:38pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/5 "2017-05-20T19:38:38Z")
i suspect the reason for the lack of coordination between the house builders and the electronics designers, is simply that they don’t bother to talk to each other. And once something is established as a de facto rule, it’s not likely to change. ---
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [May 20, 2017, 8:14pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/6 "2017-05-20T20:14:45Z")
A related question. What is the history of red for positive and black for negative in DC applications? ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [May 20, 2017, 8:36pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/7 "2017-05-20T20:36:06Z")
> [@boffking](#): > > A related question. > What is the history of red for positive and black for negative in DC applications? Probably Benjamin Franklin’s mistaken concept of something “Positive” and “Negative” about electricity. Electron flow is the opposite of Franklin’s idea of current flow. “Negative” should be black. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [May 20, 2017, 8:37pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/8 "2017-05-20T20:37:23Z")
> [@igor\_frankensteen](#): > > i suspect the reason for the lack of coordination between the house builders and the electronics designers, is simply that they don’t bother to talk to each other. And once something is established as a de facto rule, it’s not likely to change. Probably also due to the fact that house builders were building houses & installing wiring well before there were ‘electronics designers’ around. The colors used in house wiring were probably well established by then, and electronics was a different field, and didn’t pay much attention to ‘construction workers’. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [May 20, 2017, 11:35pm UTC](https://boards.straightdope.com/t/us-household-wiring/787030/9 "2017-05-20T23:35:20Z")
> [@carnivorousplant](#): > > In electronics, black wire usually indicates ground. In house wiring, why is white neutral and the black wire is hot? This is why you never let an electronics guy work on house wiring. I had a friend (aircraft electronics tech) who ran over the cord of his circular saw, severing it with the blade. Rather than splicing the cord back together, he just bought a new plug and attached it to the cord. Luckily for him, the handle was insulated and he never touched the metal frame of the saw. Saw didn’t work, so he unplugged it. He told me about it, so I took a look at it and sure enough, he had connected the green to the hot lug and the black to ground. :smack: