wire size distance limit

The home depot manaul says that 14 gauge wire can be used for upto 50 feet for 15A lines. It has to be 12 gauge for 50 to 100 feet.
Is there a way to bypass that, like adding a junction box? I may have a couple of 15A circuits that runs 70 to 80 feet, and I would like use the standdard 14 gauge wires.
Thanks.
Y.
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no. the reason you shouldn't use them is because of their resistance. #14 wire has more resistance than #12 wire and the voltage drop will be high on a long wire. you can get a 300 foot roll of #14 wire, you can physically use it but then with a high load the voltage will drop below the minimum allowed and your equipment might not work properly.
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On 15 Dec 2003 11:39:11 -0500, Yi Jin wrote:

12 ga is not much more expesive than 14
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>On 15 Dec 2003 11:39:11 -0500, Yi Jin wrote: > >> The home depot manaul says that 14 gauge wire can be used >> for upto 50 feet for 15A lines. It has to be 12 gauge for >> 50 to 100 feet. >> >> Is there a way to bypass that, like adding a junction box? >> I may have a couple of 15A circuits that runs 70 to 80 feet, >> and I would like use the standdard 14 gauge wires. >> >> Thanks. >> >> Y. > > 12 ga is not much more expesive than 14
Thanks all. The main reasons for the smaller cable is: 1. I already bought the wire. 2. 14 gauge is much easier to deal with than 12 gauge, particularly in the electrical boxes.
I guess I'll use the wire on the light circuits, which don't draw much amps. And use 12 gauge on the outlets.
Y.
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Yi Jin wrote:

I would run 12 gauge wire from the panel to the first outlet or light on this new circuit, then use #14 wire from that point on because it's easier. Or use #12 wire for the whole circuit but put #14 pigtails on all the recepticles and fixtures because it is so much easier to work with inside the electrical boxes.
I'm doing something very similar in my garage; I want #12 wire all the way to my garage door opener to minimize the voltage drop. All the rest of the wire on this circuit (going to lights and light switches) will be #14, and I'll use a 15A breaker.
Best regards, Bob
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On 15 Dec 2003 11:39:11 -0500, snipped-for-privacy@wam.umd.edu (Yi Jin) wrote:

NO. The junction box will be much worse than a straight run. If you already have the 14 guage, then just make another run with it and connect securely at both ends.
PJ
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True.
It'd be just as easy to replace the circuit with 12ga, and you can up the breaker to 20A. You can't with paralleled 14ga - because you can't be sure how well the current will divide between the two legs.
Besides, it's a NEC violation to parallel wire that small.
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Chris Lewis, Una confibula non set est
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Chris Lewis wrote:

It will divide evenly between the two legs because the resistance of copper increases with temperature. If copper had a negative temperature coefficient, one side would end up taking most of the current and would overload.

Yes it is. It doesn't need a justification.
Just replace the longest unbroken section of cable with #12, then use #14 to do the rest of the circuit, and use a 15A breaker. Short #12 wires are a PITA to work with. Long wires are not significantly harder to work than #14.
Best regards, Bob
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"Divide evenly" presuming everything is the same and the connections are really solid. Connection resistance could dwarf the conductor resistance without being a hazard by itself, and thus the positive temperature coefficient may not help (enough).

I suspect it's part of the NEC's and CEC's justification. As far as my reading seems to indicate you _cannot_ parallel wires to increase ampacity. Only to reduce voltage drop. Thus the breaker is still sized for the smallest conductor.
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Are you really going to have a 15 amp load? If you are then use 12 gauge, if not try this web page http://www.electrician.com/vd_calculator.html NEC says the voltage drop should be less than 5 volts or is that 5%. Pretty close either way
According to the calculator 12 is light for 100 feet with a 15 amp load.
I have wired homes with 14 to bedrooms,( not bathrooms) with runs of over 100 feet.
Just because the over current protector is set at 15 it does not mean that the circuit will draw that much.
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circuit is held to 3%.
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If you add a junction box, you still have an 80 foot run. Worse, you have an 80 foot run with a couple wire nuts in the middle. Intersting idea, though.
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