Can I mix 12 and 14 gauge wire in a junction box?

Greetings,

I have a 12 gauge wire (yellow) coming directly from the circuit breaker into an outlet. It's the only thing on that circuit. I need to move the outlet, so I'm going to disconnect the outlet, pull the wire through the floor (basement ceiling) and put a junction box there (I'm moving the outlet higher on the wall and don't have enough slack as is, thus I need the junction box). I plan on running two separate 14 gauge wires (white) from the junction box. It's nothing high drain, just a standard outlet and two overhead light fixtures on a dimmer. In this case, the 12 gauge wire (yellow) would be providing the power from the breaker box (to the junction box), and the 14 gauge wire (white) would be providing power to the fixtures/outlet (from the junction box)

Thanks for your help!

V

You sound unprepared to do this work, based on your statements.

If the wire from the breaker is 12 gauge, the breaker is likely 20 amp.

Unless the house was wired by uncle Joe and cousin Moe.

You cannot switch downstream to a thinner gauge 14 gauge wire, unless you intend to burn down the house someday.

The breaker is sized to protect the wiring.
Not to protect the load of the device you might plug into it.

But yes, sometimes a heavier wire than needed is used, so check the breaker first.

Also, a yellow wire is never run directly from the breaker, unless installed by an amateur.

A hot wire direct from a breaker would typically be black, but could be another dark color, blue, purple, etc.

A yellow or orange wire is an indicator that it is coming from a switch.
Sometimes red, if the switch is a three way setup with two switches.

The outlet might be fully or partially controlled by a wall switch.
Sometimes, only one of the two sockets is switched, the other side might be always hot,

White wires are only used as neutral wires, never as hot wires.

And they are never to be switched.

Please consult a pro before doing any of this work yourself.

I believe that the OP when referring to "yellow" and "white" wire is referencing "romex" sheathed cable. "Yellow" being 12 gauge and "White" being 14 gauge - I do not believe the OP is referring to colors of individual wires/conductors unless it is a conduit setup and someone used different color wires.

VYacheslav-It really is not a good practice to mix gauge wires like that. More than likely the 12 gauge is protected by a 20amp breaker thus requiring 12 gauge conductors. I would also not always go by the color of the sheathed cable to determine the gauge. Always best to read the imprint on the cable to be sure. Some older 12 gauge was white colored sheathing at one time.

If the 14ga. conductor is your choice, then change the breaker too a 15amp, unless you do not have one available, then while you are at the store, P/U some 12ga. conductor.

Yes, I was referring to white and yellow as Romex (the outer jacket or covering). 14-2 Romex is white, 12-2 Romex is yellow. My house was built in 1947 but was completely re-wired in 2005, so all of the Romex is from 2005 or newer (I've added some). I'm obviously very cautious and triple check everything, but I wasn't sure about this, so I wanted to be sure.

I just checked my circuit breaker box and it is coming from a 20 amp breaker, so it looks like I'll have to use 12-2 gauge wire (Romex) coming from the junction box as well.. Does that include all wires that are powering the devices from that junction box (2 overheads and an outlet)? In other words, even if I am daisy chaining things together, would I have to use 12-2 gauge Romex for every connection? I'm assuming so but I want to double check.

Just out of curiosity (I'm NOT going to do this), what would happen if 14-2 gauge Romex was run from a 20 amp circuit? Is 14 gauge only rated for 15 amp circuits? I assume you could use 12-2 Romex on a 15 amp circuit with no issues? Just wondering. Thanks,

V

12ga through out.

In a heavy amperage load the conductors will heat and prolonged use can subsequently de-rate the insulation, and a short will occur.

Yes, the 14 gauge wire could overheat with 20 amps running through it.
It could short out, melt, or cause a fire.

It is always ok to use a heavier gauge than required, because sometimes in the future the electrical demand might increase, and changing to a higher amp breaker is then possible.
As long as that heavier gauge was used throughout the entire circuit.

Part of the confusion of your original post is that you were using the term “wires”, when you really meant “cables”.
Plastic cables which contain several individual wires or conductors, with their own insulation which is colored, or a bare ground wire.

I just wanted to thank you guys for the answers because I did not know some of this. I'm taking notes.
I need to stop calling cables "wires".

First of all, I agree with everything that has been said. If it is 12 gauge, use that throughout. If it was 14 gauge up to the outlet, and all you had was 12 gauge, you could use that and overbuild it, although I do NOT recommend it because it will cause confusion to the next person that has to handle that, and possibly problems from there. Also, when daisy chaining, keep in mind that the resistance increases with the length of the cable. So, if the end point that you'll be daisy chaining to makes it a lot farther from the circuit board, then consider running a direct connection. (By the way, a very long connection could be a reason to go with 12 gauge (lower resistance) even on a 15-amp breaker.)

Jeff Handy said:

Part of the confusion of your original post is that you were using the term “wires”, when you really meant “cables”.
Plastic cables which contain several individual wires or conductors, with their own insulation which is colored, or a bare ground wire.

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Jeff, your knowledge and help in this forum is without equal but keep in mind that just because someone doesn't know the right names doesn't mean that they are ill-prepared to do the work. I witnessed a electric supply shop guy give a speech to a guy also because he used the wrong name for something; little did he know that that guy has a PhD in electric engineering. That guy with the PhD might not be familiar with certain specifics of the craft but I sure as hell prefer him handling the electric system in my house rather than the moron that wired it the first time.

In almost all trades region to region I find people use slightly different terminology, sometimes brand names become a generic name etc. The information is correct given above in this thread. I guess I’m getting old because I have a couple rolls of white 12-2/G & 12-3/G out in the workshop and someone had almost a whole roll on Craigslist of 12-3/G for next to nothing so now I have yellow as well.

When you think about it you run 12 or 14 up to the light Jbox and then you connect 18 or 22 to it to attach the fixture. So if the light shorts you still have some light gage wire in the circuit.

The breaker or fuse is intended to protect the house wiring, the cables or conductors (wires), not the appliances or fixtures plugged into that circuit, or attached to a ceiling box, etc.

Sometimes an appliance or device will have its own fuse, inside the plug or on a circuit board or in the cord.
Or a built in circuit breaker with a reset switch.

But otherwise, they are on their own, skinny wires and all.

Nowadays, safety improvements like gfci and afci outlets are actually moving some protection out to the user end, where the appliance plugs in.

Bud16415 hit the nail on the head with regions using different terminology.

Overall, we in this forum who assist DIYers, in my opinion try to correct an OPs terminology or clarify their intended terminology mainly so we can get a grasp on exactly what it is they are asking so we can be more apt to give them solid advice more so than putting them down and telling them they are not qualifited. Although there are times that a DIYer has made it clear in their written text or their replies that maybe the project they are involved with is a bit over their heads or that they need to do more research on it. We do this not so much to "put them down" but to make them aware of the fact that "a little knowledge can be dangerous" especially when it comes to electricity in your home.