Free Republic
Browse · Search
General/Chat
Topics · Post Article

Skip to comments.

Question about electrical supply to overhead ceiling box

Posted on 08/18/2006 3:36:00 AM PDT by rudy45

I am working on an overhead ceiling fan, which is wired to an electrical box in the ceiling. That box and fan are powered by a wall switch. Also, I have located the circuit breaker that controls that box.

Instead of turning off the circuit breaker, why couldn't I simply turn off the wall switch, if I want to avoid the chance of electrical shock? Wouldn't turning off the switch prevent current from getting to the ceiling box? Or is there still a danger of shock, even though the switch is off?

I DO intend to turn off the breaker, but still am curious. Thanks.


TOPICS: Hobbies; Miscellaneous
KEYWORDS: electricity; homerepair
Navigation: use the links below to view more comments.
first previous 1-2021-29 last
To: Lonesome in Massachussets
I know that if "you know what you're doing" you can do this safely, but the folks who really know what they're doing follow the rules.

That is right. I'd never recommend an "Edison Circuit" to anyone.

21 posted on 08/18/2006 6:04:26 AM PDT by 300magnum (We know that if evil is not confronted, it gains in strength and audacity, and returns to strike us)
[ Post Reply | Private Reply | To 18 | View Replies]

To: rudy45
Would you leave the safety "off" your weapon because you know there isn't a round in the chamber?

That being said, I used to sell electrical distribution equipment. One day, a contractor came in somewhat shaken. He was doing an easy job, and almost forgot to check if the circuit was "hot." Turns out that the entire house was wired with the black and white wires reversed. He'd been in business for 30 years and never seen anything like it.

That being said, when I was in college, I wired/installed a ceiling fan "hot." Not for the faint of heart, and you need to get used to working (primarily) with one hand.

22 posted on 08/18/2006 6:05:56 AM PDT by 1rudeboy
[ Post Reply | Private Reply | To 1 | View Replies]

To: Lonesome in Massachussets

That's what I meant about making a mistake in having admitted to it - having someone else misunderstand that as recommending that they do it, too.


23 posted on 08/18/2006 6:14:06 AM PDT by tacticalogic ("Oh bother!" said Pooh, as he chambered his last round.)
[ Post Reply | Private Reply | To 20 | View Replies]

To: Dumpster Baby

OK, wait a minute. Now you're saying that maybe there's a problem even if the BREAKER is off?? How can that be? Thanks.


24 posted on 08/18/2006 6:21:14 AM PDT by rudy45
[ Post Reply | Private Reply | To 17 | View Replies]

To: rudy45
The breaker and/or wall switches only turn off the hot line. The neutral and ground wires are not switched. In almost all cases the neutral and ground wires really are at ground potential, but very rarely they're not at ground potential due to a poor or failed ground connection at the breaker box or on the line drop coming in from the pole. The neutral and ground wires have about a 99.999% probability of being properly grounded, but one should be aware of the possibility they aren't - and take appropriate precautions against getting between ground (copper water pipes, etc) and ANY part of the circuit being worked on.

If the work is done wearing rubber soled shoes, on a wooden ladder, on a carpeted floor, etc, etc, there's very little way to establish a path to ground through your body. You should always be as insulated from ground as possible, and have the breaker and switch for that circuit turned off.

Here's a scenario: You kill the breaker on the circuit you're working on. While you have the box open you find several neutral and/or ground wires connected together with a wire nut. You have to separate those neutral and/or ground wires to make a new connection. Those multiple wires in that wire nut might be the result of two or more different hot breaker circuits sharing the same neutral and/or ground wires in the return path back to the breaker box. When you separate those grouped neutral and/or ground wires, some of them are still trying to be the return path for energized circuits on another breaker that's still turned on. This "shared" neutral and/or ground return path is NOT supposed to exist in wiring that's done properly and according to electric code, but it really does occur far more often than you would think. When you break apart multiple neutral and/or ground wires that are all supposed to be a ground potential, you may actually be "ungrounding" the return path for another energized circuit on another breaker. The "ungrounded" return path thus created will go back to ground by any path you provide it - including your body.

If this doesn't make sense, let me know and I'll try to explain it more clearly.

25 posted on 08/18/2006 6:54:06 AM PDT by Dumpster Baby ("Hope somebody finds me before the rats do .....")
[ Post Reply | Private Reply | To 24 | View Replies]

To: rudy45

The last time I did this my wife walked into the (semi dark) room and, you guessed it, turned the switch on.


26 posted on 08/18/2006 1:39:49 PM PDT by VRing (Happiness is a perfect sling bruise.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: rudy45

If you are alone in the building you may just turn off the switch. If there is another electrician or other person in the building turn off the breaker. For consistency and so that you need not worry it is best to habitually turn off the breaker.


27 posted on 08/18/2006 1:42:38 PM PDT by RightWhale (Repeal the law of the excluded middle)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Dumpster Baby

lol can I put it in language I can understand lol? It sounds like even if I turn off the circuit breaker for that box, other wires in that box COULD be associated with ANOTHER circuit breaker, and if that second circuit breaker is on, I could have a problem?

I guess to be REALLY safe, I should turn off the MAIN circuit braker? Thanks.


28 posted on 08/18/2006 2:23:23 PM PDT by rudy45
[ Post Reply | Private Reply | To 25 | View Replies]

To: rudy45
That is *exactly* the problem with SHARED neutral and ground returns, most common in older houses that have had the wiring and sockets changed here and there over the years. Ideally, each breaker's branch circuits have their own isolated neutral and ground returns not connected in any way to another circuit's returns. When neutrals and grounds are shared between switched-off and live circuits, and you undo a bundle of neutrals or grounds in a wire nut, then *some* of those neutrals and/or grounds dangling loose are still connected to ground at the breaker box and *some* are connected to live circuits. Unless you know absolutely for sure that neutrals and grounds are not shared, you need to treat each and every wire as if it could be hot while they're dangling loose.

In practice this means don't put yourself between any two wires in the box, or between any wire and a real earth ground.

29 posted on 08/18/2006 2:38:47 PM PDT by Dumpster Baby ("Hope somebody finds me before the rats do .....")
[ Post Reply | Private Reply | To 28 | View Replies]


Navigation: use the links below to view more comments.
first previous 1-2021-29 last

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
General/Chat
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson