Three-way switch installation


Old 07-21-06, 08:45 AM
Thread Starter
Join Date: Jul 2006
Posts: 7
Three-way switch installation

This is really cool. This is my first post, so hopefully, I'll provide enough info for somebody to make sense of my gibberish.
I'm replacing an existing installation consisting of two single pole switches controlling a ceiling fan, and a backyard spotlight from the kitchen (indoor), with a two three poles switches so that I can control the fan and the light from both the kitchen and the back screen porch. I had to run another wire back to the two original switch box housing the kitchen switches. I didn't have enough 14-3 wire, so I got creative and used a single run of 14-2 to get to those first switches from a gang box in the basement. From Basement gang box I was able to use 14-3 wire. The circuit is powered at the first switch, goes to the Basement Gang box, out to another gang box in the Garage (I had to break the original 14-3 that fed the Fan and Spot light, so I chose a good spot in the garage directly above the point where the back porch switches would go), then on to the Porch switches, back to the Garage gang box, and finally up and out to the Fan and light via the original 14-3 feed.
It's really the last switch box that I'm stuck with (the one on the screen porch). And of course, I'd feel better having somebody eyeball this install. I do have a brother-in-law who's a licensed electrician, but he probably won't be up to check this out for a couple of weeks.
Oh, I got into this because we decided to install two new lights on the wall of the screen porch. They are daisy-chained, switched only from the screen porch, and are powered off of an electrical outlet feed in the garage. You'll see those wires poking in/out of the switch box diagram/pic located on the screen porch.
Lots of pics. I wish I could post attachments, but it seems to be disabled, so I'll try cut and pasting my wiring pics/diagrams immediately below.
Here we go..

Basement Gang Box
Clockwise from Lower Left cable

1. Old 14-3, goes directly to Porch switch, ultimately controls Fan.
B- 3B
R – 5B
W- 3W
2. New1 4-3 run. Goes to Garage Gang Box, ultimately controls Spotlight.
B – 4B
R – 5W
W – 4W
3. 14-2, from Kitchen switch, controlling Fan
B – 2B
W – 2W
4. 14-2, from Kitchen switch, contolling Spotlight.
B – 1B
W – 1W
5. 14-2, Traveler wire for both kitchen 3-way switches. Blck=Fan, Wh=Light.
B – 1R
W – 2R

Garage Gang box
( Clockwise from Upper Left cable)

1. To Porch Sw, controls two new lights. NOT WIRED YET
2. B (Light) – 5B
R (Fan) – 3B
W - 3W

3. Porch Fan Switch
B – 2R
W – 2W

4. B – 6B
R - 6R
W – 6W

5. Porch Light Switch
B – 2R
W – 2W

6. B- 4B
R- 4R
W - 4W

Porch switch box
Left to Right

1. Not shown yet. I’ll pull this in tonight or tomorrow. This will be incoming power for the Porch switches, I guess. 14-2. I’ll pull power off the plug outlet in the garage.
B –S1, C
W – 2W
2. 14-2 outgoing. Porch switch
B –S1, C
W- S1, T1
3. 14-3, incoming from basement gang box, Kitchen Fan Switch
B – S2, T1
R – S2, T2
W – 4W
4. W 14-2, out to gang box in garage. Spotlight Switch
B – S3, C
W – ST, T1
5. 14-3 from garage gang box. Originates on Spotlight switch in Kitchen
B- S3, T1
R – S3, C
W – 3W
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Old 07-21-06, 08:58 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
I have no idea what your notations mean. They make absolutely no sense to me.

I don't like what I hear.

To go from a single switch to two three ways means running three conductor cable from the existing switch location to the new switch location where you install a three way switch, and replacing the original switch with a three way switch. The run to the new switch is wired as a switch loop. Using two conductor cable in any way to accomplish this is wrong.

In your case, you need two runs of three conductor cable from the existing location in the kitchen to the new location on the back porch.

Remove everything you have and do what I just stated. Do not use any extra junction boxes and do not use anything but 14-3 cable (assuming this is a 15 amp circuit).

Utilizing extra junction boxes, while not wrong, introduces additional points of possible failure and only complicates the installation.
Old 07-21-06, 09:27 AM
Thread Starter
Join Date: Jul 2006
Posts: 7
Sorry, my notations probably would have been somewhat clearer with pictures. But here's the secret code:


The number preceding the wire color signifies the cable that conductor is contained within. The conductor position the gangbox is defined in the clockwise order (in the pictures)
Thus the notation "1 R - 4 B", says the red wire of cable #1 is connected to the black wire of cable(wire?) 4.

The Basement gang box was already in place. It's role seemed to connect the two 14-2's originating from the two single-pole switches in the kitchen, to a single run of 14-3 terminating at the Fan and Spotlight located out on the screen porch.

The two kitchen switches are not easy to get at. They're located on an exterior wall, behind a tile counter backsplash. Rather than pull the two 14-2's, and replace them with two new 14-3's, I chose to use the existing two 14-2's already in place. A third 14-2 become the third wire (wires?) for each of the two switches, but only so far as the basement junction box. From there, the runs are indeed two separate 14-3 between the two 3-way switches.

Anyway, thanks for reading my post.

Old 07-21-06, 09:46 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973

Using a third wire in the manner you did to create wiring for three way switches is wrong. It creates a current imbalance in the three pieces of 14-2. You do not want this, and it is a code violation.

Abandon the existing pieces of 14-2 to the kitchen switches. You don't have to remove them, they can stay in the wall, just push the ends out of the boxes. Instead use 14-3 and do the installation properly.

From the sounds of things you have also created a code violation by having too many wires inside a box. This would be a fire hazard. I'm sure you don;t want to burn your house down.

One final comment, the setup you describe with the basement box being used to combine two 14-2s into a single 14-3 is in itself a problem. This should not have been done, and you should fix this ASAP.

A job worth doing is worth doing correctly.

Peter, from the sounds of your post, you need an electrician to correct the existing unsafe code violations, and to properly wires in your 3 way switches.

Last edited by racraft; 07-21-06 at 10:06 AM.
Old 07-21-06, 10:04 AM
Thread Starter
Join Date: Jul 2006
Posts: 7
ok. It'll certainly make that basement junction box a lot simpler, but I hate the idea of pulling out the dishwasher again. Oh well. Do I really have to abandon that basement junction box? Wire cost have skyrocketed (copper, I guess), and I'd prefer not to have to buy a 200ft reel of 14-3, unless I have to. The distance from basement junction box to the kitchen switches is probably less than 10 ft. The real stretch in the circuit is traveling from there out to the screen porch.

What is the code-defined limit for wires in a box?

Does anybody know the words to that song "Burnin' down the house..."?

Old 07-21-06, 10:10 AM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
If you are going to use a junction box in the basement, use a large one. Make it a square (double gang box).

Box fill calculations are not difficult, but there are many factors to consider.

Re-read my last post, as I added to it after I originally posted it.
Old 07-21-06, 11:28 AM
Thread Starter
Join Date: Jul 2006
Posts: 7
Thanks Bob,
Yes, the gang box in the basement is a big one, steel, properly grounded, and even has a lid screwed on it.

I've been wondering how that two 14-2 going into a single 14-3 works, anyway. It was fashioned by an electrician, so I assumed it's ok. It's been in service for almost twenty years. I guess the return loop coming back from either/both loads ( light and fan) share the same neutral wire. Definitely a creative job, and it'd be a real pain to re-route with two separate 14-2's to each load at this point. At least now we've cut down the distance the 14-3 goes solo from the second switch out to the light/fan loads.

As I said, I'm planning to have an electrician check this out next week. I don't know how you guys do this stuff. There's must be dozens of ways to wire a 3-way switch. All of them confusing.

Thanks again,

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