attempting to add a three way switch

leikolee · 11-10-2011, 09:07 PM

I am attempting to add a three way switch. I have 2 lights ran to one switch currently. I have pulled the switch out of the box and have noticed I have two black wires, two white wires and my grounds. The link below is the exact setup i have how can I make this setup into a 3 way setup? I don't have access to get to the last light in the circuit.

Billy_Bob · 11-10-2011, 09:13 PM

rjniles · 11-11-2011, 07:15 AM

Run a 3 wire cable from the existing switch box to the new switch location. You may have to replace the existing switch box to a larger one to accommodate the number of conductors.

Here's a diagram (bare ground wires not shown but must be connected):

Note if you are under NEC 2011, you will need a 4 wire cable to include the neutral.

joed · 11-11-2011, 08:35 AM

NOTE in the above diagram the COMMON screw is on the lower right. The common screw can be identified on the switch by being a different colour thatn the other two screws. It is usually black.

leikolee · 11-11-2011, 09:19 AM

If I add one 14-3 wire into that box then I have my power source black wire, my light source black wire then I have added a red and another black wire. There are not that many screws on a three way switch. Where do they all go on switch one?

rjniles · 11-11-2011, 09:48 AM

Quote:

Originally Posted by leikolee

If I add one 14-3 wire into that box then I have my power source black wire, my light source black wire then I have added a red and another black wire. There are not that many screws on a three way switch. Where do they all go on switch one?

In the original switch box you will have these connections( ignoring the bare grounds):

Black to the lights to the common of the 3 way switch
Black from the power feed in to the black of the 14-3
Red & white of the 14-3 to the other 2 terminals (travelers) of the 3 way switch.
Leave the other 2 whites connected as they are.

Color the white of the 14-3 with a black felt tip marker at both ends to show it is "hot"

leikolee · 11-11-2011, 09:56 AM

So now that I am making a white wire hot in box 1 how will it be wired in box 2?
White wire to the black screw on the 3 way
Red and Black as travelers?

CheapCharlie · 11-11-2011, 10:27 AM

Black wire always goes on the common screw, in both boxes. Travellers should be red/white

rjniles · 11-11-2011, 10:35 AM

Quote:

Originally Posted by leikolee

So now that I am making a white wire hot in box 1 how will it be wired in box 2?
White wire to the black screw on the 3 way
Red and Black as travelers?

No, black to the common, red & white are the travelers.

Just like the diagram I posted.

Remember what I said about the wire fill in the original switch box.

SD515 · 11-11-2011, 10:41 AM

Quote:

Originally Posted by CheapCharlie

Black wire always goes on the common screw, in both boxes. Travellers should be red/white

Not true. The white can be re-marked to feed the switch.
From the 2011 NEC:

200.7 Use of Insulation of a White or Gray Color or

with Three Continuous White Stripes.

(C) Circuits of 50 Volts or More.

The use of insulation

that is white or gray or that has three continuous white
stripes for other than a grounded conductor for circuits of
50 volts or more shall be permitted only as in (1) and (2).
(1) If part of a cable assembly that has the insulation permanently
reidentified to indicate its use as an ungrounded
conductor by marking tape, painting, or other
effective means at its termination and at each location
where the conductor is visible and accessible. Identification
shall encircle the insulation and shall be a color
other than white, gray, or green. If used for single-pole,
3-way or 4-way switch loops, the reidentified conductor
with white or gray insulation or three continuous
white stripes shall be used only for the supply to the
switch, but not as a return conductor from the switch to the outlet.

leikolee · 11-11-2011, 11:05 AM

thanks guys got it.

rjniles · 11-11-2011, 11:05 AM

Quote:

Originally Posted by SD515

Not true. The white can be re-marked to feed the switch.
From the 2011 NEC:

200.7 Use of Insulation of a White or Gray Color or

with Three Continuous White Stripes.

Actually that is the way I prefer to do 3 way switches by remarking the white as the power feed and using the red & black as travelers. The sketch I found on line used the black as the power feed so I went with it.

Remarking the white as hot is also consistent with a switch loop using the remarked white as the power switch feed.

But NEC 2011 will make all this go away with the requirement to bring a neutral to all switch boxes.

jeffnc · 11-11-2011, 01:55 PM

The cables in the top 2 diagrams do not have to be 12 gauge as they imply.

Billy_Bob · 11-11-2011, 02:40 PM

Note that when I am installing entirely new wiring, the walls are open, etc....

Then I like to just run the wires needed for the switch to the switch electrical box. And make all those connections elsewhere like at a light fixture or a junction box in the attic.

Or use an extra deep electrical box. (More room.)

Or I might use a 4 inch square electrical box with a single gang plaster ring. (Lots more room.)

I understand you are working on existing wiring, so you may not have the above options. But if you do, then maybe one of those suggestions might be helpful...