Ok to mix wire gauges?


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Old 10-07-04, 05:42 PM
Whiteknight55
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Ok to mix wire gauges?

I realize the problem with using smaller gauge wire in a circuit that has a larger gauge, (i.e. adding 14 gauge to an existing circuit that uses 12 gauge), but what about the reverse? I have some left over 12 gauge and I would like to add an outlet to an existing 14 gauge line, assuming all connections and components are approved for 12 gauge? Thanks.
 
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Old 10-07-04, 06:05 PM
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You could use any size wire you like, as long as you protect it at the lowest capacity value for the smallest wire in that circuit. For example, if you have a 15A breaker serving #12CU then #10CU then#14CU then the receptacle, that's ok, because the 15A breaker is the correct size for the smallest wire (#14CU)
 
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Old 10-07-04, 06:09 PM
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Angry Thats my question too!!!!

I just found out that my (while unemployed) wiring job (doing EXACTLY what you speak of) was totally rejected such that the HEAVY lines 12-3 7 12-2 needed to be replaced with 14-3 & 14-2 "in Lowell area of MA". (I USED THAT LINE BECAUSE THE OWNER HAD PLENTY OF IT) I am outraged and confused so please someone post a reply. I know that it varies per town and state but what is the deal in general and WHY? Thanks in advance.
 
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Old 10-07-04, 06:11 PM
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oops 12-2 is bigger than 14-2. Fat fingered it.....

oops 12-2 is bigger than 14-2. Fat fingered it.....
 
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Old 10-07-04, 06:13 PM
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Thanks HandyRon

That is what I figured.... Can't figure this inspector out....
 
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Old 10-07-04, 08:27 PM
J
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racket7, I'm not sure what kind of response you are looking for. Although the NEC has nothing against mixing wire sizes as long as the smallest wire size is big enough, many municipalities do require all wire on the circuit to be the same size. Either they are worried about future mistakes caused by confusion, or they are just trying to simplify the job for their inspectors.
 
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Old 10-08-04, 05:14 PM
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Regardless of what anyone has "left over", there is no reason at all to intentionally mix wire sizes. It's just not necessary. If you have left over wire keep it for the next project you will more than likely do.

As to being tagged for it. ???? Maybe it actually is a local code, in which case you have nothing to do but comply.
 
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Old 10-09-04, 10:02 PM
hex2k1
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while reading this post something else (relevant) came to mind that i never really thought about. article 210 has a couple of tables 210.21(b)(3) & 210.24 that state that you can have recepticles rated 15A on a 20A circuit provided you have more than one recepticle on a circuit. now that being said is it permissible to feed the 15A recepticles with 14 awg provided you feed your first recepticle with 12 awg and mix and match wire sizes accordingly to the recepticle ratings down stream. this is just for personal knowledge not for installation purposes. i thought it would be a good question to discuss. i had a similar question when i was testing for electrical certification in california.
 
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Old 10-10-04, 05:04 AM
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You cannot have 14ga branch circuit wiring protected by a 20A breaker, even if you are feeding a 15A receptacle. There are situations where smaller gage wire can be on a 20A breaker, eg the 'fixture wires' for a lamp, but these exceptions never apply to receptacle outlets on general purpose circuits.

Remember that most common 15A receptacles are duplex receptacles, and you could in theory plug in two 10A loads.

Also note that the 15A receptacle is rated for 20A feedthrough; the only thing 15A about it is the _shape_ of the hole arrangement, so as to restrict the loads which may be connected to the receptacle.

-Jon
 
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Old 10-10-04, 07:08 PM
hex2k1
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Jon thinking about it some more you should have 12 awg wiring throughout the circuit for the simple fact that if you make your first recepticle 20A the next one 15A and a third one 20A you could in theory draw more current from the third recepticle than the 15A wiring (14 awg) can handle and we dont want to do that. i guess i got into reading the code a little to much and forgot about the common sense aspect of it.
 
 

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