The person who wired the lighting in my new kitchen used #12 wire and is using a 20amp breaker. The kitchen contains 5 cans, 3 pendant lights, and undercabinet lighting. I believe he also wired in 4 more cans and a ceiling fan/light from the new sunroom as well.
Someone told me that it is not good to use #12 wire for lighting. Why is that? Also, this person said it is not good to use #12 wire with a 15amp breaker. My contractor is using a 20 amp breaker, but I was wondering why it is “bad” to use a 15a breaker and #12 wire. This someone said the breaker won’t work correctly with a combination of #12 wire and a 15a beaker. I don’t get it. I would think a 15a breaker will trip when more that 15 amps goes through regardless of the wire guage.
Am I missing something?
Replies
using 12 ga wire for a lighting circuit with a 15 amp circuit is just fine. In fact it exceeds code which call for a 14 ga wire.
My opinion is that #12 wire is good (all them engeneers can't be wrong?) We see it spec'ed on most commercial jobs.
The only down side is terminating #12 can be tough to bend and splice on the smaller wire some fixtures use, but thats no big deal.
Having it on a 15 amp breaker shouldn't matter at all.
Anyone else?
who ever told you that is misinformed, #12 w/ 15amp breaker is fine, it is #14 with a 20amp breaker that is a problem
Sometimes you need 12 (or 10) gauge on a 15A to reduce voltage drop due to an excessively long branch circuit run. I have a 15A Square D QO breaker on my desk that indicates it is suitable for 1 or 2 10-14 gauge conductors. The device doesn't know what gauge conductor is connected, only the current passing through it.
Be seeing you...
Don't use a 20 amp breaker for lighting circuits even with 12 ga wire in Chicago. My house had been rewired with all 12 ga wire and 20 amp breakers (by a licensed electrical contractor). I recently converted the attic to living space (two bedrooms and a bathroom). The electrical inspector made the (different) electrical contractor change all of the 20 amp breakers on the existing lighting circuits to 15 amp. The inspector stated that even though 12 ga wire was used, the wiring in the light fixtures was not rated for 20 amps (kind of agree given the cheesy wiring in most fixtures).
The wiring in the fixtures ain't rated at 15 amps either.
It is probably more like 6-10 amps.
But SO WHAT!!!!!
Where are you going to find a 720 watt light bulb to over load the fixture wiring, not to mention the 1800 watt bulb to max out the 15 amp circuit.
The fixture is UL approved to used on a 20amp circuit. That is all the inspector needs to know.
What about the recptacles. Did you have to change those to 15 amp breakers also. You could plug a lamp with #18 wire in the recptacle.
Simply speaking, the guy was an idiot. Or to give him the benifit of the doubt he head something about this and never reasoned it out.
I agree, but still had to change it.
Unfortunately your inspector is pushing his authority a little too far. I think it should have been agrued higher up the chain.
The wiring in the fixtures ain't rated at 15 amps either.
It is probably more like 6-10 amps.
But SO WHAT!!!!!
So says the NEC, also (1996, anyway), unless I've read it wrong. Article 240-4 Protection of Flexible Cords and Fixture Wires. "...Fixture wire shall be protected against overcurrent in accordance with its ampacity as specified in Table 402-5.", which says that 18 gauge fixture wire has an allowable ampacity of 6A, but Exception No. 2 to 240-4 states "20 Where fixture wire is connected to 120-volt or higher branch circuit of Article 210 in accordance with the following: 20-ampere circuits, No. 18, up to 50 ft ... of run length."... Article 410-24(b) goes on to require fixture conductor size to be "... not smaller than No. 18.", along with other mentions of insulation, temperature, and the like.
I could be way off base here, but I've always taken that to mean you can connect lighting fixtures to 20A branch circuits. I'm not an authority on the subject, so I'd like to be straightened out if I'm wrong.Be seeing you...
Well I can say my 50 y.o. houseoriginal service panel had only 6 circuits and they were all 20 amp incl. the lighting circuit and no problems (of course it might need a little updating ) :>)At Darkworks we measure twice cut the cheese once
"I could be way off base here, but I've always taken that to mean you can connect lighting fixtures to 20A branch circuits. I'm not an authority on the subject, so I'd like to be straightened out if I'm wrong."
First I am not sure that wires being discussed are "fixture wires". One would have to really understand the WHOLE code and read the notes of the writting commitees. My "impression" is that the light fixture it'self is listed by UL and that defines the heat resistance of the wiring, etc and that a UL approved light fixture is suitable to be wired to the branch circuit.
Reading 402-10 and 402-11 (99 NEC) I get the impression that fixture wires are wires that you can run from the branch circuit to whatever connects are provided by the fixture manufacture.
But even if I am wrong the section that you call out is proof that the lights can be used on 20 amp circuit.
This inspector needs a remedial circuits class!
Fixtures have 18guage wire...rated at something much larger than they actually pull...right? For recessed cans, you might have a 150W bulb tops...because of thermal problems...and that's just over 1 amp. Since they are wired as drops on the line...the fixture wiring never sees more than this 1 amp or so. Never close to 15A, unless you short the socket!
So why would there be an issue?
Never have more than 15A flowing in a 14 guage wire...20 in 12guage. Never design for the limits either!
.....Never close to 15A, unless you short the socket! ...
I always figured this is exactly why the Code wants the 14-gauge to be protected by a 15-amp breaker: for short-circuit protection. With the newer 90-degree rated insulation on NM-B romex and thhn we know that #14 even embedded in a cable could handle 20 or so amps safely. But looking at the overcurrent/time curve of a circuit breaker shows that there could be enough more of a time delay under short-circuit conditions that there would be more chance of damage/fire if the larger breakers were to be used.
I could be wrong, but like I said that's what I've always figured about it.
Ed
The only down side which comes to mind is that #12 is a bit, not much, more expensive and difficult to work with. In some areas, for no logical reason that I know of, #14 is not allowed as house wiring at all. The entire house is then wired in #12 or larger. I have no problem with this. I just leave the #14 at the shop and bring extra #12.
The general rule, with very few exceptions, is that any circuit containing #14 house wiring, excluding fixture wiring and extension cords, must be protected at 15A or Less. #12 protected at 20 or Less.
Do not, as some have suggested, put any circuit that has any #14 wire in it, with the previous exemptions, on a 20A breaker. There are cases where this is both justified and according to code but most of these are fairly rare conditions dealing with dedicated motor circuits or A/C and should only be implemented by someone trained to make the call. An electrician or HVAC tradesman.
The chances of a #14 wiring bursting into flames and causing the fall of the western world are pretty slim. Even though I won't do it, with anything less than a large caliber gun held to my head, I have seen it many times. On the other hand it only takes one small fire, once, to hurt someone you love. Be safe.