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# Connecting at Junction Box 14/3 to 12/2

#1
01-04-07, 12:06 PM
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Join Date: Jan 2007
Posts: 2
Connecting at Junction Box 14/3 to 12/2

What is the correct procedure for connecting 14/3 (older existing) wires to new 12/2 (new renovation) at a junction box. This is the only 14/3 in the house and it feeds a 3way and 2way foyer/entry lighting switches.
Regards, Dave

#2
01-04-07, 12:18 PM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
The best way to wire a new addition is new circuits all the way back to the panel, or perhaps even a sub panel.

Generally, you do not attempt to attach to three conductor wiring, as three conductor wiring typically means a three way switch is involved.

Generally you do not mix 14 gage wire and 12 gage wire on the same circuit.

I suggest you do the right thing and run a new circuit.

#3
01-04-07, 01:40 PM
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Join Date: Jan 2007
Posts: 2
14/3 to 12/2 at junction box

racraft,
Thanks for your response. The 14/3 is a problem and we would replace the new 16 feet of 12/2 with original 14/3 to complete the circuit.
Regards, Dave

#4
01-04-07, 02:46 PM
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Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Dave, I do not understand your last post.

#5
01-05-07, 10:51 AM
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Join Date: Jan 2004
Location: Oregon
Posts: 1,219
You have two issues confused here.

14/3 means 14 gauge wire (the size of the wire) with _3_ conductors in the cable (possibly plus a ground)

12/2 means 12 gauge wire (thicker wire suitable for higher current) with _2_ conductors (possibly plus a ground)

There are good reasons not to mix 12ga and 14ga wire, but it is code compliant to do so if you use a 15A breaker. There are specific situations where benefits from mixing the two wire sizes outweigh the negatives, but I won't go into them at this time.

The real question is 'why do you have _3_ conductors'. You need to figure this out prior to doing anything else. A circuit requires 2 conductors plus ground. 3 conductors means something more complex is going on.

You could have 3 conductors for any of the following reasons:

1) Multi-wire branch circuit, where _2_ circuits are run in a single cable with a shared neutral. In this case you need to run 3 conductor cable back to your panel and wire it correctly.

2) 3-way traveller switch legs, where the cable is between two three way switches. In this case the cable needs to be run to the other switch, not back to the panel.

3) Spare conductor. The contractor had 14/3 on hand, and simply used it to provide the possibility of future expansion.

4) Switch leg. There is supposed to be a switch somewhere that you've removed. One conductor is supposed to be full time power, the other is supposed to be switched.

5) Monkeys. You never know what monkeys will do ( *grin* meaning some other reason that I've not imagined)

You need to figure out what the other end of these conductors are connected to, and only then can you define how they should be extended to/connected in your panel.

-Jon

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