When wiring up normal 3-prong outlets, does it matter if I switch the black and white wires on a single outlet in the run?
I've heard the polarity doesn't matter...but want to make sure I'm not going to short it out or something else horrible.
Also, when wiring up lights, does it matter which color wire I run to the switch? Most of the how-to articles show cutting the white wire...does it make any difference?
Yes, it does. Don't do it.
You didn't hear that from anyone who knows what he's talking about. Polarity
*does* matter. Among other things, you could wind up making the housing of whatever you plug in there, live.Yes.
No, they don't. You'd better look again. The switch should always go on the hot side, which (in the US and Canada, anyway) is the black wire.
It matters.
It matters. And I doubt your last paragraph correctly describes those articles.
The concern relates to safety and failure modes. Either way will appear to work. But the wrong way will be unsafe and violate code.
Yes it matters that the white wire goes to the larger hole side of the outlet and the black wire goes to the smaller hole side of the outlet.
Then when things are plugged in, they are safer if the outlet is wired properly. For example a table lamp with one prong larger than the other. You can only plug it in one way. The larger prong (white wire) goes to the "ring" part of the light bulb. The smaller prong (black - hot) goes to the switch and then to the contact down in the center of the socket.
You can get electrocuted if you touch the black hot wire. It is safer it this is the wire going to the contact in the bottom of the light socket. It is easy to accidentally touch the metal ring of a light bulb when changing a light bulb. Best if it is connected to the white (neutral) wire and NOT to the black hot wire!
So wire your outlets properly and wire lamps and appliances properly. Get a book on wiring or call an electrician. These things are done to protect YOUR life and the lives of YOUR family.
In addition to what was written above, your nonstandard wiring would pose a problem for anyone who worked on it inthe future.
It matters. That is why they use different colors.
Not only does it matter, it can be unsafe, it is against all known codes and it can cause your home to fail inspections. You don't want to do it.
kj:
The black wire (which can be any color, actually, except white) is the 'hot'. The white or 'natural gray'-insulated wire is the 'neutral'. Think of the 'hot' as a permanently pressurized 'pipe', and the neutral as a 'drainpipe' which only carries electricity when the 'faucet' (switch, appliance, etc) is using it.
Now, lights and other plug-in appliances are designed so that the 'hot'
is less accessible than the 'neutral'. Ex.: the bulb 'shell' is connected to the white 'neutral', and the contact at the socket bottom is 'hot'.
This ensures that if somebody is removing a dead bulb with the light switch still on (for instance) and brushes against the shell, they are unlikely to get a shock (unless something else is wrong with the wiring). If the hot and neutral are reversed, this shell would be connected to the 'supply pipe' and not the 'drain pipe', and the user would be shocked. (Note that it is still possible to get shocked by a neutral, but it is less likely).
Moral of the story: Safety dictates that hot and neutral must be properly connected. Follow the manufacturer's directions. If for some reason it's easier to do it the wrong way, that's too bad. Do the job right.
Now for switches. Switches must always control the 'hot' side of a circuit, cutting off the 'supply pipe'. That way, with the switch off, the only unbroken connections (if the light is properly wired) are to the 'drainpipe', the neutral side. When a switch is in the neutral it will still stop current from flowing; the light will turn on and off with no problems. However, even with the switch off, all terminals and wires in the lamp will be 'hot', part of that pressurized pipe of electricity, waiting for somebody to provide a path to ground. ZAP.
Moral of the story: Switches must be in the 'hot' wire, never the neutral. This is a common problem in old houses, where some damfool cut off and reconnected an old K&T run (where the conductors may be hard to tell apart) without bothering to check which was which.
There is one situation where you may find a white wire on a switch. Power may go to a lamp or other switched outlet,then out to a switch and back to the outlet on the two conductors of one cable. This is known as a 'switch loop'. If you find a switch with only one
2-conductor cable coming into its box, and something goes on and off when you flip it, you are definitely dealing with a switch loop. In a switch loop, all wires are considered 'hot'. If using cable, code allows the white wire to be used as part of a switch loop, but it is not a neutral, is not connected to any other neutrals, and must be permanently reidentified some other color where the wire is exposed inside the boxes.Story time. My brother found an (overstuffed) j-box with a questionable receptacle in it, in a basement. Removing the receptacle, he proceeded to wirenut all whites and all blacks together, then turned on the power. All well. Then he flipped the basement light switch. ZAP. One of the white wires was actually part of a hacked switch loop. He had created a bolted short. Unfortunately, the circuit was also part of an absurd multiwire circuit (which split 6' from the service panel) which was equally hacked, with overstuffed boxes, insecure connections, and puny wire nuts, and one leg of this circuit was overfused. Both breakers tripped. My brother, being sensible, switched off the offending light, and turned the breakers back on. Well, some lights went poof, and the phone, and some other electronic gadgets, now acted really funny in a not-working way. Apparently the neutral of the multiwire circuit had failed somewhere. Rather distressed by this, he shut off both breakers (I told you he had sense) and we later straightened everything out. This involved replacing one 4" octagon box with two
4S boxes and eliminating such idiocies as the elusive "switch threep"- one wire to the switch, one wire from the switch to each of two boxes, using two pieces of 12-2 with one wire unused. Ugh.
Moral of the story: learn what you are doing before you do it. There are good books out there. Get a permit and get your work inspected. It costs less than burning the place down. Finally, don't use USENET as your sole source, and definitely don't use the home center. House wiring is not as simple as some think.
Cordially yours: G P
Hire a qualified electrician.
Yes. Correct it.
It's not polarity (this is AC, where polarity is changing 120 times a second), but connecting it right still matters.
I guess I missed those articles. I always switched the hot (black) wire, the obvious way to do it.
or green?
One time, while changing a switch, I held a hot wire and felt absolutely nothing. I was careful not to touch anything else electrical at the same time.
They do have a lot of people who don't know much.
Yes, it does make a difference.
As another poster mentioned, switch on the wrong wire allows switched devices, such as lamp sockets, to be hot - you get shocked if you touch such items and ground.
As for outlets - those have designated hot and neutral terminals that should not be reversed. Many appliances have polarized plugs. If a lamp has hot and neutral reversed, then the exposed part of the base of a partially screwed-in lightbulb will be hot - even if the lamp's switch is off!
Also keep in mind that in some fluorescent lamps, reversing hot and neutral can adversely affect the electric field distribution within a bulb that is trying to start, and that may impair starting.
- Don Klipstein ( snipped-for-privacy@misty.com)
To be safe & meet code, all 120V outlets will be wired with the neutral (white) connected to the neutral terminal on the outlet, indicated by the silver screw; hot (almost always black, sometimes red) connects to the brass colored screw; and ground, which is bare or green insulated, connects to the green grounding screw on the outlet. (or to the grounding screw of the outlet box, if box & outlet are designed for this; usually the case when metal boxes are used)
If by "switch the black and white wires" you mean connect them opposite to above description, then doing so will create a potentially unsafe condition. OTOH if you mean to install a switch to control that outlet, then only the black or hot wire should be switched. The neutral or white should always connect directly to the outlet. In either case, there is only one correct way.
The term "polarity" has to do with positive & negative, and is important in direct current systems, e.g. automotive. It really has no bearing on a discussion of alternating current house wiring.
As far as connecting a light to a switch, there are a couple different ways the wiring can be routed, that will make a difference as to which color wire should go where; However, in all cases, the current carrying neutral will connect to the neutral of the light fixture and is never switched.
Why not get a good DIY book on house wiring? There are several that do a good job of explaining both safe wiring and safe work practices. Black and Decker sells a good one.
Please, hire an electrician.
OP doesn't necessarily have to hire an electrician, but does need more knowledge before attempting to DIY this job
Electricians aren't born with their knowledge. They have to learn it. There's no reason a person of ordinary intelligence cannot learn, in a reasonable length of time, how to safely perform simple, basic tasks like wiring an outlet, switch, or light fixture.
In short, yes it matters, and you have to know why. Home Depot and Loew's sell good books on home wiring.
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