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  1. #1
    Join Date
    Jul 2008
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    Default Different Gauges of Wire

    How do you determine what Gauge of Wire to use for projects ???. I had some 12/3 left over from an old project and was wondering if I could safely use it fro wiring your common Wall Outlet. I may also use it for "stealing" power from one outlet to power a switch leading to a cieling fan....could this be a problem ??....or is this OK to do

  2. #2
    Join Date
    Aug 2007
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    Default Re: Different Gauges of Wire

    Rule of thumb ......

    14 gauge copper wire is appropriate to use on regular circuits combined with a 15 amp breaker/fuse.

    12 gauge copper wire is appropriate to use on circuits conbined with a 20 amp breaker/fuse.

    however ...... you can use the heavier gauge wire for a lower rated circuit ..... 12 guage wire for a 15 amp circuit is fine.


    Hope this helps.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Jan 2008
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    Lakeland ,MN
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    Default Re: Different Gauges of Wire

    Quote Originally Posted by Beer Belly View Post
    How do you determine what Gauge of Wire to use for projects ???. I had some 12/3 left over from an old project and was wondering if I could safely use it fro wiring your common Wall Outlet. I may also use it for "stealing" power from one outlet to power a switch leading to a cieling fan....could this be a problem ??....or is this OK to do
    If you are not sure of the wire size the jacket covering the wire should be marked.
    example is a non metallic cable is typically called romex (old brand name) would be marked 14-2 type NM which means it has a black wire , white wire, and a bare wire this is used on 15 amp circuit.
    a 14-3 type NM would have all the wires mentioned above and also a red wire.
    Harry

  4. #4
    Join Date
    Sep 2008
    Location
    Indiana
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    25

    Default Re: Different Gauges of Wire

    Quote Originally Posted by Beer Belly View Post
    I may also use it for "stealing" power from one outlet to power a switch leading to a ceiling fan....could this be a problem ??....or is this OK to do
    It should be fine as long as the addition doesn't exceed the existing circuit's allowed amperage.

    For wiring receptacles, 12-3 is a little overkill unless you are putting receptacles on different circuits, alternating between black and red. I wired a master bedroom with double duplex receptacles (left black, right red). The bedroom had two separate 20A receptacle circuits.

  5. #5
    Join Date
    Jun 2007
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    Default Re: Different Gauges of Wire

    Although 12 ga. is rated at 20 amps, if any of the other wiring is 14 ga. the breaker for the circuit must be maintained at 15 amp. You can always use larger wire in a circuit but fusing or breakers have to match the smallest wiring used in the circuit. And if you use larger wire do not use the stab connections, connect the wires to the screws. This is a prefered practice even if you are using the right size wires.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Jul 2008
    Posts
    62

    Default Re: Different Gauges of Wire

    Thanks for the replies. Looks like I'm gonna be fine.

  7. #7
    Join Date
    Aug 2008
    Location
    British Columbia, CANADA
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    46

    Default Re: Different Gauges of Wire

    Beer Belly:

    One other issue with using 12/2 or 12/3 wire for connecting ordinary 15A receptacles and switches:

    the thicker gauge wire will likely require heavier wire nuts (aka "Marettes") to join them together. You may find that when all the wires are connected together, there is not enough room to stuff them back into the box. They are alot stiffer, and getting everything to fit might be a real problem.

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