# mixing 12 & 14 guage wires



## bethany14 (Jan 25, 2007)

It's ok to mix these, right?  I'm using scrap for the new porch lights and some are 14 and some are 12.  I can't think of why it would be a problem, but thought I'd check here.
Thanks!


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## glennjanie (Jan 25, 2007)

I know one local inspector who will not allow it because another electrician in the future may want to tie into the #12 wire thinking it is a 20 amp circut while the #14 is generally used for 15 amp circuts.
It won't hurt your work; its just for future reference.
Glenn


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## bethany14 (Jan 26, 2007)

good, thanks.  I hadn't thought of that...
Thanks Glenn, you're always here for me


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## Kerrylib (Jan 26, 2007)

Code does not allow wire gauge to change size.  Typical lighting circuits are 14 awg.
As glenn mentioned someone might see 12 awg and assume a 20amp circuit


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## petey_racer (Jan 26, 2007)

Kerrylib said:


> Code does not allow wire gauge to change size.


Who's code? Can you cite a section of code to support this??? I have NEVER heard of this being illegal. 
As far as an inspector "not allowing" it. I would politely ask him for a code reference as well. Contrary to popular belief, inspectors cannot simply prohibit us from doing things because they "don't like it".

Absolutely it is bad practice, but as long as the breaker is sized for the smaller wire there is nothing illegal about it.


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## Daryl (Jan 26, 2007)

As one who owns a home built in 1900 which has seen several "upgrades" it is not unusaul to find old heavier wire attached to lighter wire when a circuit was extended. I have also found new homes (less than three years old ) where I have opened up a 15amp receptacle (on a 15 amp breaker) to extend another outlet and found to my surprise 12 gauge wiring. Yet another circuit (15 amp) on the same level was ran with 14 gauge. After finding this more than once I always go by the circuit breaker in the box and not the wire size. I totally agree that they should not be mixed, just find it hard to see how they would reinforce 12 gauge not being used on a 15 amp circuit. Of course using 14 guage on a 20 amp is a no no but oversize on a smaller circuit seems to be used frequently even in new homes.


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## bethany14 (Jan 27, 2007)

If you know the circuit you're working with, it seems to me you'd go by the breaker size, not the wire guage, just like Daryl says.  And if you don't know the circuit you're on, you should find out.  And then look at the breaker.
If there is a problem with it, then I'm in trouble because the circuit I extended already had 12 guage, though it's a 15amp circuit.  When I extended the circuit I re-used some of the 12 guage, but mostly used 14 guage.  To correct it I'd have to go back through the PO's old work, back through my whole house.  I'll let you guys know what the inspector says...


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## Hube (Jan 27, 2007)

Kerrylib said:


> Code does not allow wire gauge to change size.  Typical lighting circuits are 14 awg.
> As glenn mentioned someone might see 12 awg and assume a 20amp circuit


_____________________________________________________________
When it comes to working  on  Electrical, you don't assume anything, you make sure by either  definite visual or  instrumentation checks.

Assumptions can sometimes lead to bad injuries.....(zap!)


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## Square Eye (Jan 27, 2007)

Code ..

LOL


I used to mix wire sizes often, sometimes because code requires it!

On very long runs, I would upgrade wire size to try to avoid voltage drop.
When Sharing a neutral I would upgrade the neutral.
When I had more than 3 circuits in one conduit, I had to upgrade.
And even in residential, I would often run all of my home runs to the panel in #12.


When you feel that you have a good reason for doing so, the inspectors I dealt with always let a larger than required wire size pass.

BUT

On a new home, seeing #12 and #14 mingled and mixed would probably get any inspectors attention. If he feels that you have no pride in your craft, he may decide to go over your job with a fine tooth comb. To avoid problems, make your jobs as neat as you can


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## bethany14 (Jan 28, 2007)

Here's the deal though, the original circuit was run in 12!  It's 15 amp circuit that runs receptacles and lights.  I bought 14 guage (which is the correct wire size for a 15 amp circuit!!!), and ran most of my new work in that.  When I started tearing out the front wall I pulled about 20ft of #12, and we're too cheap to let that go to waste   Welp it's all in there now, so we'll see.
Hopefully he/she understands, I definately see your point Square Eye...
<CROSS FINGERS>


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## Kerrylib (Jan 29, 2007)

I must humbly admit I misspoke.  I can not find any specific code references to mixed wire sizes within a branch circuit.  The closest I see is a reference to NO provision allowing a smaller conductor as a switch loop in a 20 amp branch circuit.

Wiring simply must be sufficient for the ampacity of the circuit protection.  Generally 14 awg is used on 15 amp circuits and 12 awg on 20 amp circuits.
A receptacle that is rated for 20 amps is not allowed on a 15 amp protected circuit, whereas a 15 amp receptacle is allowed on a 20 amp circuit.

I appoligize for my mistaken comment.

Thank you to those who corrected me for providing some good clear explainations to go along with the chastizing.


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