I had a rough electrical inspection and was told I cannot mix 14-2 and 12-2 wire on the same circuit. Is this valid? Why?
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Replies
Depends on what is downstream from what. My inspector, at least, allowed me to use 12-3 for a three way switch even though the lighting circuit was fed by 14-2...just because that's what I had on hand. But in this case the heavier wire is downstream from the lighter wire.
The reason, though, that they don't allow you to wire 14AWG downstream from 12 AWG is that there is potential for overheating the 14 AWG with a load greater than its capacity...before the breaker trips. So the rule is to protect the wiring in the wall.
It's confusing because it's perfectly OK to wire a lighting fixture that has, say, 16 or 18 AWG feeders to a 20amp 12AWG cicuit. But that lighter wire is outside the wall. Similarily, it's common to use a 14AWG extension cord plugged into a 20amp 12AWG circuit, but, again, that lighter extension cord is outside the wall. Will it still melt before the breaker trips? Maybe maybe not, but presumably you will notice something awry before it catches fire. Maybe not so if it was in the wall.
At least that's the way I understand it.
Edited 3/9/2004 12:12:11 PM ET by johnnyd
"It's confusing because it's perfectly OK to wire a lighting fixture that has, say, 16 or 18 AWG feeders to a 20amp 12AWG cicuit. But that lighter wire is outside the wall. Similarily, it's common to use a 14AWG extension cord plugged into a 20amp 12AWG circuit, but, again, that lighter extension cord is outside the wall. Will it still melt before the breaker trips? Maybe maybe not, but presumably you will notice something awry before it catches fire. Maybe not so if it was in the wall."
That is partically it.
But for permanately fixed things like light fixtures they are still concealed.
The NEC only covers the wiring up to the fixture. The fixture is covered by UL listings.
But also look at it from a logical standpoint. While you might drastrically over lamp the light fixture you would probably have a hard time putting in more than 300 watts of bulbs in a fixture and the small wire can still carry that safely. (But the heat from the bulbs would fry the wire, socket and probably the rest of the room).
But also look at it from a logical standpoint. While you might drastrically over lamp the light fixture you would probably have a hard time putting in more than 300 watts of bulbs in a fixture and the small wire can still carry that safely. (But the heat from the bulbs would fry the wire, socket and probably the rest of the room).
That's why I think it should be allowed to go ahead and wire a switch leg to a light box with 14 AWG, even though the switch box is fed with 12 AWG! But Nooooo.
I suppose someone COULD stick a screw-in recepticle in there and load it up even more....
"That's why I think it should be allowed to go ahead and wire a switch leg to a light box with 14 AWG, even though the switch box is fed with 12 AWG! But Nooooo."
But that is on the NEC part of the system.
The main problem with doing that is not the any direct safety issue, but they you have great confusion about how the system is being wired. And you can always run more lights off the first one.
Likewise is switch box that I am moving. It is in the center of 2 3-ways and 2-4ways. Power comes to this box and the lights controlled by the switches are run from this point. So all of the wiring between the 3-ways and 4-ways are "switch legs". And I did the whole thing with 14-3 because a) there is only lamps on this circuit and b) it is reto work and I did not want to have to snake and pull 12-3 in a bunch of odd locations.
Now if I had mixed 14-3 switch legs and feed it with #12 wire there would have been nothing, but confusion as to what was really going on.
" Is this valid?"
Not exactly.
You are limited by the size of the overcurrent protection (circuit breaker). 15 amps for #14 and 20 amps for #12.
Long runs or derating might require a larger wire size. So in case like that you might run #12 for a long run and then at the end have #14 wire going to the outlets. But that would be limited to a 15 amp.
Otherwise mixing 14 and 12 is legal if you limit it to 15amp breaker, but mixing it without any reason would be seen as "bad practices".
Only a non professional electrician would do that. But it would be OK if its on a 15 amp breaker not a 20 amp. Those that mix wire tend to make electrical inspectors check even harder, because its a sign of a amateur electrician. Its armature wiring that kills people.
When someone sees # 12 wire, they wont know #14 is upstream and will think its normally on a 20 amp breaker not 15 amp
As others have said you cannot have 14 gauge wire anywhere in a 20 amp circuit, except in a light fixture in which case it might even be 16 or 18 gauge. Go figure.
I think the inspector was busting your balls because you're doing it yourself and he didn't like the look of it. If he knew you were a licensed electrician he might have let it slide... as long as the breaker was right.
The trouble with just having the breaker right on a mixed 12/14 circuit is that if some unknowing person has to replace that breaker in the future, they may look at the #12 wire in the panel and think "Oh, here's the problem. This should have been a 20 amp breaker." So they put in a 20 with #14 downstream on the circuit.
-- J.S.
The breaker is a 15amp on the #12wire but it is a single line to the garage door opener only as the garage required one home run. Therefore, if the breaker is changed to a 20amp then it is only an upgrade I suppose.
All the 14ga is downstream from the 12ga. Is this an acceptable condition as all of the thinner 14ga was existing wire in the house that runs back to 15amp breakers. In the instance where I added a line used the 12ga. which made sense to me since the longer runs out to the garage would be more efficient.
Yeah, there should be an exception for when heavier wire is used for a long run. But I don't know that there is.
So why not run 14AWG from a 15 amp breaker to the first box, or a junction box, and then if you want to, run 12AWG from there to wherever. No-one would mistakenly replace that breaker with a 20 amp, and if somone tapped into the 12AWG thinking it was a 20 amp circuit, it would still be protected, and if they tried to run a big load on that and the breaker kept tripping, they would soon find out what was up...They would be (&%^%'d though....so I do really see why the no-mix rule.
> All the 14ga is downstream from the 12ga. Is this an acceptable condition
No. This is what could lead to a breaker replacement mistake.
-- J.S.
what everybody has said is correct, cannot mix wires, It would be illegal here. They are trying to make 14 ga illegal here, make everything 12, lights, everything. they have already made 12/3 illegal in the kitcern circuit.
That's what I do, make everything 12. Easier than bothering with two different kinds.
-- J.S.
I notice that all the new #12 wire is yellow. I'm guessing that this is a new rule to make it easier for the inspector to tell which is which.
i like the idea that every thing runs on 12,but i got into box fill problems on some 3and 4 way light circuts. so i wired the entire circut with 14. will put a 15 amp breaker on it.does this seem like a logical solution to box fill problems or should i have done something different? larry
>> ... or should i have done something different?
Deeper boxes? Two gang boxes with single gang mud rings?
I might not have the jargon exactly right on that. I saw it in FHB years ago. Contractor used only deep 4" square boxes, even for one switch or one duplex outlet. Said it reduced the number of different parts he had to carry and eliminated wire fill problems. Made a lot of sense to me.
Edited 3/10/2004 2:15:05 AM ET by Uncle Dunc
That's a 4" square box (called 4S or in some areas, a "1900" box 'cuz that's the part number...). Use a deep one and a mud ring (single or double gang) , and you'll have room to spare--even with 12 gage wire.
Using a 4S and a mud ring also allows you to orient the receptacle horizontal, which some people think looks cool for the kitchen countertop receps.
Cliff
I am guessin the mud ring goes on b4 sheetrock..other wise ya got 4" holes cut out?...
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Whatever winds your clock.
I always rough in with 2 gang metal boxes (Raco bracket boxes to be specific) and then use mud rings. I'm not one of those guys that can twirl three feet of #12 wire inside a single gang box along with 5 wire nuts and make it all look like it grew there. Mud ring goes on before the rock and I usually back bevel the hole in the rock with my knife (not using a rotozip) so that the mud ring is tightly surrounded.
Dang, wish y'all had said this stuff about 2 weeks ago..I just now am getting my rock..all the boxes are insulated in..oh well, next time.
Thanx for the info.
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Sphere,
Yep, 'lessin you're a mud artist.
Had one case where I was working wirh an owner-builder, and he said he'd put the mud rings on in the kitchen. Got most of them oriented the same way. He became a mud artist. Saving grace was that the wall was tiled.
Cliff
How about 4 11/16" square boxes?
-- J.S.
Agreed--if the wire in the panel is #12 then all the wire in that circuit should be #12. I was imagining that the #12 was mixed in somewhere mid-circuit and buried in a wall. Even so, someone could come along later and tie into the #12 and think they can run a 20-amp load on it. I'm not saying it's good practice to mix them, and most of the time an inspector would ding it, except maybe if they know the electrician and he's got a reason for it. Mainly it's just what might happen if you run out of #14 wire.
Even if you wire the circuit to a 15A breaker, the inspector will worry that someone will see the #12 wire coming into the breaker panel and assume that the breaker can be swapped out for a 20. I think some inspectors will allow the mixing if the wires in the panel (and anywhere else where confusion might occur) are specially labeled, but many won't allow it, or even having #12 downstream from #14.
After all, it's a lot easier to enforce a rule if you never allow for exceptions.