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sherlock 06-30-2006 11:33 AM

How do I add switch to pull-chain light
In my basement I have an unfinished room that has 2 pull-chain incandescent lights. I intend to change them out with flourescent light fixtures. I will also need to add a switch. There are a couple of things downstream from the current lights - one is an outlet, not sure where the other one goes as it goes up through the ceiling.

How do I add a light switch into this circuit so that it turns the lights on and off, but doesn't affect the rest of the circuit?

IvoryRing 06-30-2006 12:11 PM

Your circuit will branch at the light. One branch of it goes downstream, the other branch goes to the lampholder and then out to the switch.

The way I would wire this, and have done so at the light over my main panel...

At the box where the light is:

The incoming EGC (bare) gets wirenutted to the box, to the outgoing EGC and to the EGC in the cable going to the switch.

The incoming neutral (white) get wirenutted to the outgoing neutral and a pigtail that goes to the white/silver screw on the lamp base.

The incoming hot (black) gets wirenutted to the outgoing hot and to the black on the cable that goes to the switch.

This leaves only one wire unaccounted for in this box - the white in the switch cable. This I wrap with a piece of black electrical tape (i.e. you are marking the insulation of this wire as 'not white' -- you still strip to the copper) and then wire to the yellow/brass screw on the lamp base.

At the box for the switch, I wire the EGC (bare) to the box, then the white gets a piece of black tape wrapped around it, and then wired to the switch. The black also gets wired to the switch.

sherlock 06-30-2006 12:29 PM

Ok, thanks for the explanation. I understand the process for one light, but not sure I can extrapolate for 2 lights. Now, where do I put in the wires for the 2nd light if I want the single switch to operate both lights, and still leave the downstream items unaffected? Is there a way to insert the switch cable at the downstream light? It's closer to where I want to install the light switch.

IvoryRing 06-30-2006 01:26 PM

Oops, you did say 2 lights, didn't you... Let me paint a picture to see if I understand you correctly... the cable runs like this:

A - panel
B - first light
C - second light
D - downstream devices

You now want to have a switch near C, which controls both B & C.

If that's the case, you'll need to replace the wire between B & C. You likely have 'black/white/bare' there now, you need to replace it with one that has black/red/white/bare. If your current cable is 14/2 wg, you need to replace with 14/3 wg, if it currently is 12/2 wg, you need a 12/3 wg. The red in between the two will be a traveller (sorta).

At B, black comes in and gets wirenutted to the downstream black, not stopping at the lamp itself. white comes in and goes to a wirenut with a pigtail for the lamp (goes to white screw) as well as the downstream white. The red running to C goes to the brass screw on the lamp. Bare comes in, goes to a wire nut, which as a pigtail for the box as well as the bare going downstream.

At C, upstream black comes in and goes to a wirenut with black to the switch as well as black going downstream to D. upstream white comes in and gets wirenutted to downstream white as well as a pigtail going to the white screw on lamp base. coming from the switch, your white gets relabelled as black (well, for consistency, I'd probably use red tape in this case), wirenutted to a pigtail that goes to the brass screw on the lamp and also to the red wire coming from B. EGC (bare) comes in and gets wirenutted to a pigtail for the box, as well as the bare for the switch cable and the bare going downstream. If it was me, I'd probably get a box extension for C.

At the switch, it's just a matter of EGC to the box, black to the switch, white taped as red and to the switch.

In both cases, I would tape over the lamp screws after making the connections before assembling the box - with all those bares in there I'd be likely to end up shorting to one of the 4 screws.

By the way, the switch being closest to B or C makes no difference - you could wire it either way.

sherlock 06-30-2006 03:01 PM

Actually, hot power comes in to the first light, then downstream peels off to the left, and wire to 2nd light peels off to the right. but based on that description, I think I can figure it out from here. Thanks again. Will see if I can find time to do this over the long weekend.

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