installing a basic light

[Cheeky]

what is the best way to install a light (new fixture, no hook-up):

i have a light switch at the top of my basement stairs that controls the basement lights. there is no light at the top of the stairs, and i would like to install one. somebody told me to run a line from one of the lights downstairs and back up. is this the best way, or is it possible to safely do it off the line from the light switch at the top of the stairs?

[LarryG]

It will depend on where that switch is physically located in the circuit. You'll need a hot (black) and a neutral (white) conductor for the new light. If the switch is electrically "upstream" of the existing lights, the switch will interrupt the black wire and the incoming and outgoing white wires will be tied together in the same box. (IOW, the white conductors will simply pass thru the switch box, using it as a junction box; the switch will not interrupt the white conductors.) If this is the case, then you can fish a wire from your new light to the switch box and tie the black and white conductors to the ones that are already there.

If, however, the switch is "downstream" of the existing lights, there could be a black wire on one of the switch's two terminals and a white wire on the other. This is what is usually called a "switch loop" and it means that you'll have no neutral conductor available for the new light (even though one of the wires is white). In this case, you'll have to tie the new light into the existing lights.

[Tequila]

Here's a simple way to tell. Take the cover off the switch and pull the switch out of the box (turn off the breaker first of course). If the only wires in the box are connected to the switch, then you've got a switch loop and will need to connect to the light downstairs.

If there's extra wires in the box, then you'll almost certainly be able to connect the new light directly from the switch box.

[Cheeky]

thanks guys.

i opened up the switch, and there are 2 sets of wires. one set has a red, black, white and ground. the red and black goes to the switch (although the black is also tied to the black from the other line), and the white from that one is tied to the white from the other set (the second wire set has black, white and ground, which appears to be going downstairs to the lights).

[jessrice]

is this a 3 way switch, is there another switch at the bottom of the stairs to turn the lights on and off from either the top or bottom?

[LarryG]

the red and black goes to the switch (although the black is also tied to the black from the other line)

Hard to know without seeing it, but I will hazard a guess that there's an outlet (or outlets) on this same circuit with the lights; or other lights on the same circuit that are controlled by a different switch. The black wires are connected together so that the outlet(s) or those other lights will be hot regardless of the state of this particular switch. The additional red conductor goes to the basement lights and allows them to be switched on and off independently of whatever else is on this circuit.

[TheRic]

Cheeky you will need to find out what wires are coming from the panel box / which ones are hot. If you have a voltage tester, and know how to use it, it should be easy to find out.

I think Larry is correct, but there are several other options. In old houses I have seen some VERY strange wiring.

[Cheeky]

Hard to know without seeing it, but I will hazard a guess that there's an outlet (or outlets) on this same circuit with the lights; or other lights on the same circuit that are controlled by a different switch. The black wires are connected together so that the outlet(s) or those other lights will be hot regardless of the state of this particular switch. The additional red conductor goes to the basement lights and allows them to be switched on and off independently of whatever else is on this circuit.

geez, you're good.

i turned off the switch on the box marked basement lights. it looked like all the outlets in the basement still worked (the basement lights were killed). but when i came upstairs and hit the switch for the dining room light, it didn't work. then i realized that an electrician added a light in the dining room a couple years ago (ceiling fixture, none existed before), which explains why one of the wire sets goes up to the ceiling, and most likely over to the dining room.

i want to learn/understand wiring and electrical work so bad.

[crokett]

Cheeky, based on the above for the new light, pull a cable from the new light fixture to your switch box

At the light: connect black wire to black lead on light and white wire to white lead on light. wrap black tape around the white wire to show that it is switched hot.

At the box: connect the black wire to the red wire coming from the switch. connect the white wire to the white wires coming from the basement lights. Wrap black tape around the white wire coming from your new light to show it is swtiched hot.

You said you want to learn electrical basics. If you want an explanation why it is wired this way, PM me.

[reddog552]

try this link

Im going to try to post this site . I have had friends that used it helped themhttp://www.electrical-online.com/wiringdiagrams.htm I am a Industrial electrican of 30+ years

[LarryG]

At the light: connect black wire to black lead on light and white wire to white lead on light. wrap black tape around the white wire to show that it is switched hot.

At the box: connect the black wire to the red wire coming from the switch. connect the white wire to the white wires coming from the basement lights. Wrap black tape around the white wire coming from your new light to show it is swtiched hot.

I agree that this is the way to wire the new light, but unless I'm missing something ... why would you wrap the white wires with black tape??? To my knowledge that's only done when the white conductor is used as a hot lead, typically for a switch loop at the end of a run. That's not being done here. The new light is simply being added on in parallel to the existing lights.

[crokett]

Larry,

I've always done it to show the white wire is hot and not being used as a neutral. At the light at least it is on the hot leg of the circuit, so it gets taped. I was taught that as a teen by an electrician friend of my Dad's.

[TheRic]

But the white wire WILL BE the neutral, NOT hot!! The hot will be the black wire out of the box, the white will give you neutral to the light. The hot is coming from the box, NOT the light. There is no switched hot. The black is either hot or dead at the light, depending on the switch being on or off.

Said another way, at the light if the white is a switched hot, then what is the black wire?? Where is the neutral???

I think you need to look at it again.

[LarryG]

David, if that's truly what you were taught, you were taught wrong. Ric is 100% correct: the white in this case IS a neutral; it is NOT hot. It can't be. If it were hot and you tied it to the neutrals at the switch box, you'd have a direct short at that point.

If the white were hot, and needed to be marked with black tape, then so would the whites for the existing lights. Electrically, they are no different than the wiring for this new light.

You may be confusing the new light in this situation with a new switch. With a switch, at the light the incoming (from the panel) black wire would be tied to the outgoing (to the new switch) white wire, which would be marked with black tape (or other method) to indicate it is hot. It goes to the switch as the "send" wire and the black conductor in the same jacket is used as the "return" wire back to the light. This allows the connections at the light itself to be entirely normal: black wire (returning from the switch) to black on the light, white incoming wire (from the panel) to white on the light. In this scenario, in which the new switch is at the far end of the circuit physically, the white wire going to the switch must be taped to indicate that it was used as a hot as a matter of convenience (because the white conductor is already there, in the jacket, with nothing else to do).

[crokett]

Ric/Larry,

I know that the white wire is indeed the neutral return to eventually the breaker box. However I was taught by an electrician who always advised me to consider both legs as the hot until the wire gets back to wherever the switch was. He told me that it would make it easier to figure out wiring and that one day it would save me from some trouble. He was right on both counts.