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for USA, Canada and countries running a 60 Hz power supply service.Running single conductor wire with two-wire cable for a three-way switch is illegal.

(LIFE SAFETY WARNING! [disclaimer]

Electricity is dangerous!

You can be injured or killed!

Improper installations can cause fire, injury and death!

Should you be doing this yourself?)

This is one of those questions - if you know this little, you shouldn't be doing what you are planning...

No disrespect intended, but this is SO basic that it suggests you have not studied the subject at all!

The practice of running an additional conductor along with the cable to give you enough wires for a three way is illegal and unsafe.


Install three conductor cable with ground.

For information on how to hook-up one light with two on-off switches, see the Related link "How to wire a 3-way switch, including a wiring diagram", shown below.


By asking this question you are probably not quite ready to take on this particular task. The correct answer to your question will depend on the exact locations of the switches and the switched fixture, its voltage and its power rating.

If you get any other answer here, you might attempt to do something you shouldn't be doing, and that may cost someone a shock, a home fire, or even their life.


As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.




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โˆ™ 2015-07-15 18:28:54
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Q: For a 3 way switch can a 3rd wire be added that isn't encased in the romex wire if it's the same gauge?
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Related questions

Can you use single conductor 14 gauge wire to wire a three way switch?

The key is the protection of the wires. If you are using single wires you will need a conduit of some sort. Don't just run the single wires in the wall. Multi wire Romex or metallic shielded cable are used to provided added protection to the encased conductors.

What gauge wire is romex?

Romex is a manufacturer's wire cable trade name and not a wire size.

What is the difference between thhn and romex?

THHN Is used in conduit, Romex is not.

How do you wire a light and switch with the 2 wire old romex?

with a standard 1 pole light switch (one switch operating the light) it is black wire to black wire and white to white (non grounded)

Can you add 14-2 romex wire to old house wiring?

Yes, if the existing wiring you are adding to is 14 gauge. If it is 12 guage then you must use 12 gauge. If you are running wire from the service panel it is fine as long as you install a 15 amp breaker.

How many watts and romex gauge is safe for a 15amp breaker?

Assuming 120 VAC in a residence maximum watts = 15 x 120 = 1800 Watts. For a continuous load you can support 1440 watts which is 80&amp; of maximum. You need 14 AWG gauge wire.

Is romex pure copper?

Copper or aluminium.

What is Romex wire?

ROMEX&reg; is a federally registered trademarked brand of non-metallic sheathed electrical cable originally developed by the former Rome Wire Company in 1922. The ROMEX Brand is now owned and produced by Southwire Company.

What size romex for 5000 watt dryer?

Assuming 220 volts service 5000/220 = 22.72 Amps. That equates to 10 AWG Romex.

What wire is commonly used in house wiring?

Romex, All you have to do is go to a hardware store and tell them you need house wire. It comes in a box. I am not sure how many feet. If you are just looking for the gauge, they will know that too.

What is romex in electrical terminology?

type NM cable

How do you wire a three-way switch when the power supply is in the light box?

to wire a 3-way like this you first need to run 14/3 romex wire from the light box to each of the 2 switch locations. at each switch connect wires as follows: white wire to common screw(usually black or brass) connect red and black wire to silver colored screws, does not matter which way. in the light box you need to identify you incoming power, once you have identified that wire connect one of the white wires from the new 14/3 romex to it,secure with wire nut.the red and black in each 14/3 romex are connected red to red, black to black. this should leave you with one white wire frm a 14/3 romex, this connects to the black wire of your light fixture, the white of your light fixture connects to the white of the incoming power wire.

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