installing a 3 way switch to existing single switch

I would love to be able to turn on my garage light from inside the house. I am willing to sacrifice a non related switch on the opposite side of the wall, directly behind my existing single garage switch.

Will additional wiring need to be run from the garage light or can I wire directly from the existing single switch?

does anyone have a link that may be able to show me the easiest way to accomplish this?

 

Is this an attached garage? If so easiest is to run a three conductor cable (plus ground) between the two switches. Then run power to one switch with a two conductor cable and run power to the light from the other switch using a two conductor cable. How ever there are other ways. With out knowing if power currently comes in at the light or switch it isn't possible to say which method best suits your situation.

Below uses cable but since you list Chicago your local jurisdiction may require conduit. When you apply for a permit ask if you can use flexible metallic cable or non-metallic cable. It will be easier then EMT.

 

Ray, the OP is from Chicago. He probably needs everything in conduit.

 

Thanks. I didn't notice that. I've added a note to the post.

 

Ray, this is a really clear illustration of wiring a pair of three-ways. Thank you for the link. I do wish they'd included a wire tying each of the switches to ground, though.

 

BLD, to answer the question you asked in your title, >>installing a 3 way switch to existing single switch,

 

According to at least one pro here the switch does not need to be grounded if it is a metal box and the box is properly grounded.

 

I hear that a lot, Ray. It may be true, but I always tie ground to the switch. Then, and only then, is it grounded when it's not attached to the grounded metal box. Just in case some dummy -- like me -- re-energizes the circuit before I've got everything re-mounted!

 

Hello BLD

Here is a quick Drawing that I made. That I think will work for you..
Also I wrote a few directions on how to wire your switches.
Follow Rays picture on how to connect the Ground Wires

You can use all the existing wiring as is. But of course you still need to run a new 14/3 or 12/3 cable from the location of the existing switch to the location of the new switch. Suppose "X" and "Y" represent the two existing wires connected to the existing single pole switch. Buy a pair of new 3-way switches. Put one (called switch "A") at the location of the existing switch.
Put the other (called switch "B") where ever you want the new switch. Run a new segment of 14/3 or 12/3 cable between switch "A" and switch "B". Connect "X" to the common screw on switch "A" (common screws are usually black in color). Connect "Y" to the black wire of your new 14/3 or 12/3 cable. Connect the red and white wires of your new 14/3 or 12/3 cable to the other two screws on switch "A". At switch "B", connect the black wire of your new 14/3 or 12/3 to the common screw, and connect the red and white wires to the other two screws. There may be other wires in box "A" not shown in the drawing. (white neutral wires twisted together or Green Grounding wires. Leave these wires alone. DO NOT MESS WITH THEM. )

If the “Y” wire happens to be white, mark the ends of it “BLACK” with a marker or tape

USE 14/3 + Ground for a 15 amp breaker

USE 12/3 + Ground for a 20 amp breaker




Hope This Helps


Have A Nice Day


Linesman

 

Linesman, that's thw way I would do it, with one slight difference. I would tape-tag the white wire in the new cable black and splice it to the hot feed wire. I would tie the red and the black wires on the new cable to the terminal screws on each switch. At the existing switch location, I would splice the neutrals as you have shown and terminate the load hot wire to the point screw on the new switch. At the other box, I would terminate the white wire from the new cable to the point screw on the new switch there, after tape-tagging it black.

IOW, I would convert the neutral to a current-carrying hot wire and retain the red and black as the travelers.

 

Linesman's picture and instructions are fine, unless you are in a location that uses the 2011 code. Then a neutral is required in every switch box.

For more info about grounding switches to metal boxes see 404.9(B)(1) (2008)

(B).... Snap switches shall be considered to be part of an effective
ground-fault current path if either of the following conditions is met:
(1) The switch is mounted with metal screws to a metal
box or metal cover that is connected to an equipment
grounding conductor or to a nonmetallic box with inte-
gral means for connecting to an equipment grounding
conductor.

 

Thank you, Tolyn. My take on that is that the code is one thing and good practice is another. I explained in my original post why I always tie switches to ground -- I want the protection to be there when the switch is not mounted to the box. I can understand why it's not required. The code is primarily concerned with the safety and reliability of electrical devices and systems when they are complete and in use. The reason that I will do it whether the code requires it or not is that I'm also concerned about maintaining the highest degree of safety I can while someone is working on the system.

 

You are correct. I just want to differentiate between what is the code, and what is personal practice/opinion. There is nothing wrong with your procedure.

 

That is also why some posters don't rely on self-grounding receptacles and always attach a ground wire although it isn't always required.

 

The picture below is the single switch that currently controls my garage light. I hope this makes it clear where the power is coming from

This next picture is the switch inside the house and directly behind the garage switch. This is a 3 way switch that controls a light in the laundry room.

this is a pic of the garage light, its switch to the right of the door.

is tiny url not allowed here for some odd reason?

 

Nope. Tiny urls are not allowed on this site. Post your pictures on a hosting site like photobucket and link them here.