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bethany14 01-25-2007 11:33 AM

mixing 12 & 14 guage wires
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.

glennjanie 01-25-2007 02:46 PM

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.

bethany14 01-26-2007 07:41 AM

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

Kerrylib 01-26-2007 01:40 PM

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

petey_racer 01-26-2007 02:37 PM


Originally Posted by Kerrylib (Post 7712)
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.

Daryl 01-26-2007 08:28 PM

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.

bethany14 01-27-2007 07:03 AM

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...

Hube 01-27-2007 02:13 PM


Originally Posted by Kerrylib (Post 7712)
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!)

Square Eye 01-27-2007 02:34 PM

Code ..


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.


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 :)

bethany14 01-28-2007 06:22 AM

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...

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