pauls340
Well-known member
Is it OK to use 12-2 wire with a 15A breaker?
12-2 wire with 15A circuit?
- Thread starter pauls340
- Start date
dimarcelli
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- Jan 3, 2013
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- 45
Yep.
ddawg16
Well-known member
Yep.....done all the time. The electrical guys I talk to say that is all they use....instead of keeping two types of wire...they keep just the one....the difference in cost is not that much to them.
I think the exception is when they are running 3-wire...then they will use 14/3.
I think the exception is when they are running 3-wire...then they will use 14/3.
Speedy Petey
Well-known member
This make absolutely no sense unless they are only using 20A breakers.
For a DIY with some 12/2 left over and adding to an existing circuit or something like that it's fine. For a new install, unless you are trying to avoid excessive voltage drop there is NO reason to use a 15A breaker for #12.
Now this is just stupid. This prevents them from using a 20A breaker at all. The #12 is simply wasted.
The logic of some people amazes me.
ddawg16
Well-known member
The 3 different electrical guys I talked to recently told me that is what they do....
It's not what I did....I ran 14/2 for lighting....and 12/2 for outlets....I'm a cheap ba$tard.....plus the 14/2 is easier to work with....especially up high....
It's not what I did....I ran 14/2 for lighting....and 12/2 for outlets....I'm a cheap ba$tard.....plus the 14/2 is easier to work with....especially up high....
Aceman
Well-known member
It's a waste but there is nothing wrong with it.
PhysicsDude
Well-known member
12/2 is for 20A circuits, 14/2 is for 15A circuits. But of course you can use 12/2 for a 15A circuit, its just a waste.
For a garage I always put in 20A circuits. For the rest of the house 15A will do the job...
For a garage I always put in 20A circuits. For the rest of the house 15A will do the job...
Speedy Petey
Well-known member
Oh, I get that.
What I don't get is a professional electrician intentionally mixing #12 & #14 on a new install.
robertwhite
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- Feb 10, 2010
- Messages
- 433
Just had to ask if 14ga is common in other parts of the country today? My area is as backwoods as it gets, but you best not have any new work with 14ga in it.
jvitez
Well-known member
America is differnt than Canada. We use mostly 14/2 here. CEC says lighting circuits must be 15 amp max for residential work. We do quite a bit of multi-branch wire circuits too, using 14/3.
Nothing wrong with using 12 gauge wire protected by a 15 amp breaker, you're just not getting the maximum benefit of the thicker wire. Good for motor loads though and long runs where voltage drop is excessive.
Nothing wrong with using 12 gauge wire protected by a 15 amp breaker, you're just not getting the maximum benefit of the thicker wire. Good for motor loads though and long runs where voltage drop is excessive.
Dick in Wisconsin
Well-known member
Even the kitchen (coffee maker, toaster, 3 roasters, George Foreman, electric griddle, microwave) and bath (hair dryerS, curling ironS) outlets?
justanengineer
Well-known member
There is a perfectly good reason for it - you size the breaker for the load, not for the wire, so putting in a 20A breaker when you should have in a 15A could lead to issues.
Every electrician I know uses nothing but 12 ga partially for the reason ddawg mentions, it doesnt add squat to their cost (they pass it along to you), and if you ever need to upgrade you can without having to replace the wiring. Its simply good practice.
The 2 required kitchen small appliance branch circuits are required to be 20A, and since the adoption of the 2005 NEC the required bathroom receptacle(s) have to be 20A also.
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pattenp
Well-known member
This statement is just not right. Over current protection is sized to protect the wire(circuit). The circuit which is the wire and devices are sized to the load. And there's nothing wrong with having a 20A breaker on #12 wire if the load is less than 15A.
4xyota
Member
About to wire up my garage and im really thinking of running 12/2 wire on a 20 amp breaker for my plugs now
ishiboo
Well-known member
Around here 14/2 is quite common and I use it for ALL lighting circuits/etc. 12/2 is harder to work with, especially in switch boxes with several switches.
I use it by default in all receptacles, but in my experiences 15A is almost always enough for a receptacle circuit where the receptacles/circuits are properly done.
No, he's right... the breaker is sized for the load. The wire is sized to support that load. The point is even if you run #12 for convenience, you shouldn't automatically put a 20A breaker on it... it depends on how you are utilizing it.
I use it by default in all receptacles, but in my experiences 15A is almost always enough for a receptacle circuit where the receptacles/circuits are properly done.
No, he's right... the breaker is sized for the load. The wire is sized to support that load. The point is even if you run #12 for convenience, you shouldn't automatically put a 20A breaker on it... it depends on how you are utilizing it.
pattenp
Well-known member
ishiboo
Well-known member
What about if it's #8 with a known 15A load? Should you breaker for 15A or 40A? How is it possible the NEC allows 16 gauge extension cords to plug into a 20A circuit?
EVERYTHING is sized based on the anticipated load. You selected the wire size based on what that load would be, right? Wire size is also often sized due to voltage drop and not just ampacity. The reason is breakers protect from fault conditions resulting in overcurrent - which may not be over what the wire can handle, but it can be more than the device(s) on the circuit should be using.
It all comes into play.
pattenp
Well-known member
I'm glad you're reading all of that in it. I didn't see the part where he said the wire is sized to the load.
Falcon67
Well-known member
Your last sentence makes no sense - the device on the circuit uses what it uses. The breaker protects the wire, not the device. If the 15A device goes rogue/shorts/etc, the trip will be to protect the wire. If a 1A lamp catches fire at 10A but doesn't create a fault, the 20A breaker on the run cares not.
If you pull #8, might as well breaker at 40A because if you limit it to 20A, the n why did you pull #8 - unless its for voltage drop and nothing else?
ishiboo
Well-known member
I gave him the benefit of the doubt.
It sounded like how an EE or someone with basic knowledge describes the process and not so much an electrician.So... why not have 30A and 40A receptacle circuits on larger wire, with receptacles that have a higher pass-through? Because the lower you can reasonably limit the current at the breaker, the less fault current those devices can pull... thus the "safer" things are.
With receptacle circuits especially any idiot has have the opportunity to plug any size extension cord into them with no knowledge of electricity... so while the building wiring may be able to support 30A with no problem, two space heaters on a 16ga cord may not.
Why do you think many appliances have fuses in them if one can assume they're protected by the breaker?
For any wire leaving the panel there is a maximum sized breaker that can feed that wire and the breaker is there to prevent an overcurrent condition that will harm the WIRE. You design the circuit to handle the load but size the breaker to protect the wire in the building. The load connected to the circuit will (should) have its own protection.
lg
no neat sig line
Spudland_Dave
Well-known member
Getting back to the OP...I've heard the only place you can NOT use a 12-2 mixed in with 14-2 wiring, is right at the panel.
Long story short, if you used a piece of 12-2 to get to your first device, and then its 14-2 after someone could come along down the road and see that piece of 12-2 and assume the entire run is 12-2 and swap the breaker out to a 20A...which is an issue. So IN the panel it does matter.
No clue if thats covered in code, but made perfect sense to me. PERSONALLY I dont mix and match anything. 14ga-15A for lighting circuits, 12ga-20a for normal receptacles.
Long story short, if you used a piece of 12-2 to get to your first device, and then its 14-2 after someone could come along down the road and see that piece of 12-2 and assume the entire run is 12-2 and swap the breaker out to a 20A...which is an issue. So IN the panel it does matter.
No clue if thats covered in code, but made perfect sense to me. PERSONALLY I dont mix and match anything. 14ga-15A for lighting circuits, 12ga-20a for normal receptacles.
SlappyWhite
Well-known member
Just some additional thoughts:
-12 is good 20A so obviously it will not be an issue for 15A.
-It is a waste of money (and copper) but if this is not a concern then so be it.
-Make sure the receptacles are rated to take 12 (physically), they should all be fine but make sure.
-If the idea is it may be upgraded to 20A in the future the local code may not allow lights on a 20A circuit (here it is not allowed), so keep this in mind.
-Larger conductors may impact box loading and air space, just keep in mind, specially if using small boxes.
-It will be harder to stuff everything in the box.
-it will reduce the number of wires in one connector (marette), so you may have to use bigger ones.
-12 is good 20A so obviously it will not be an issue for 15A.
-It is a waste of money (and copper) but if this is not a concern then so be it.
-Make sure the receptacles are rated to take 12 (physically), they should all be fine but make sure.
-If the idea is it may be upgraded to 20A in the future the local code may not allow lights on a 20A circuit (here it is not allowed), so keep this in mind.
-Larger conductors may impact box loading and air space, just keep in mind, specially if using small boxes.
-It will be harder to stuff everything in the box.
-it will reduce the number of wires in one connector (marette), so you may have to use bigger ones.
pattenp
Well-known member
I know what you’re saying but your example is not realistic. If I have #8 wire and over current protect it at 40A then any outlet on that circuit would need to be rated at least 40A, so that negates plugging in any 15A equipment. If I did over current protect the #8 at 15A then I’d be limited to 15A outlets. Bottom line is that the statement “you size the breaker for the load, not for the wire” is wrong in itself. There’s more to it than that.
KPSquared
Well-known member
I don't care about most of this thread but the claim that the cost difference is mimimal b/w 14-2 and 12-2 is crazy. 14-2 Romex is $67 for 75 metres and 12-2 Romex is $97 for 75 metres. . .that's like a third more.
I guess on a big project a few hundred bucks is negligible but on a small job is could be a big hit.
I guess on a big project a few hundred bucks is negligible but on a small job is could be a big hit.
Speedy Petey
Well-known member
You're an engineer, so I'll speak slowly, over explain things, and use much larger and more complicated words than necessary so you can understand me.
By using 15A breakers on #12 you are simply wasting 5 amps of potential circuit capacity, NOTHING more.
The others have already explained that this is wrong.
My point is WHY "upgrade"????? If you run #12, use a 20A breaker. The load connected to that #12 DOES NOT CARE if the breaker is a 20 or a 15.
By using 15A breakers on #12 you are simply wasting 5 amps of potential circuit capacity, NOTHING more.
Speedy Petey
Well-known member
This is just plain dumb.
There are several reasons to use #14 on residential lighting circuits, and even some receptacle circuits. Money of which is near the least important.
And if you have a problem with carrying both #12 and #14 on your truck you are not a professional and need a bigger truck.
What if you need to extend an existing #14 wired circuit? Just throw some #12 in there and call it good? NOT me.
I think the "#12 minimum" crowd just has a blind "bigger is better" mentality.
matt151617
Well-known member
I use 14 gauge on my lighting circuits. It's way overkill to use 12 gauge, and 14 is much much nicer to work with. The outlets that really require closer to 20 amps are on their own circuit anyways.
pattenp
Well-known member
1Garageman
Well-known member
This was the best answer from the beginning.
Ya i was just wondering why I read about 20 other answers to that question.
theoldwizard1
Well-known member
That is exactly what I did when I rewired my daughters kitchen !
Rosco
Well-known member
I run 12-2 for everything because I like yellow
Its generally considered a poor practice to do what you mentioned, but there is nothing per say against it in the code book (at least the 2008 version). The breaker is sized off the anticipated load. The wire is sized off the anticipated load. Do many electricians use 12 gauge in a 15 amp circuit? Absolutely, it's done because of the reasons the guys mentioned but also due to heat distance relations etc. A breaker should never be upsized without absolute knowledge of the entire circuit and the gauge/length and to include the box devices to just just starters. There is so much more to it than what gauge is running into the main panel.
wssix99
Well-known member
This is not necessarily true. ALL of the posts (unless I've missed something) are not addressing voltage drop.
Depending on the length of the run on the circuit, code requires moving to a larger wire to reduce the resistance in the circuit and deliver an acceptable voltage to all of the outlets.
A 14ga wire is fine for a short 15A circuit. A longer one may require 12 ga and may even require 10 ga for a super long one! The NEC has tables where these sizing can be looked up.
BTW - I'd never hire an electrician who installs 12 ga on all 15A circuits because they are too lazy to do the math. With the price of copper and wire these days, (thank you China) I'd be paying them to waste my money. (I'd also be wasting a precious resource, which would provide more clout to a few developing countries, which are currently working to manipulate the commodities markets and put the US in a weaker monetary position... but that's a deeper discussion.)
The cord itself is already limited to 15A because it has a 15A plug on it. Extension cords are also made from stranded wire, which can carry a little more power than a solid wire safely. Since the cord is shorter than the wires in the wall and is presumably at the end of the circuit, there is some additional engineering leeway there. However, the cord could contribute to voltage drop. For this reason, the extension cords will come with maximum wattage/amperage ratings on them to keep things safe and this is also way code doesn't allow us to wire up our main circuits with extension cords.
That too. lmao
Falcon67
Well-known member
Me too! But the last 250' had a different shade and now the lines in the attic kinda clash.
I used 12-2 because it just wasn't worth buying a roll of 14 for a few bitty runs. One kind of wire in the pile was good enough.
justanengineer
Well-known member
Sorry fellas, somehow I lost track of this thread until tonight....
Not sure if you read the OP, but we know the wire is sized BEYOND the load. Thus, you size the breaker to the load, since the wire's integrity is given as being safe. No, my statement isnt true in ALL situations, but very few statements are.
Thank you kindly for cutting me a bit of slack, and you read my point exactly. In the case of household wiring where you have codes and hardware differences to protect you some of this stuff is admittedly a bit redundant, but in an industrial setting, a lab, or overseas being a bit paranoid and developing safe practices is important. Cant say I will ever regret being "too safe" tho some of these internet jockeys may regret not being so.
Since you are accomplishing nothing by being a **** and missed the same things that several others did in the OP, I too will speak slowly and hopefully with a bit more clarity....
My statement that you quoted about "upgrading" referred to oversizing wire to plan for the future possibility of having a larger load, and avoiding the cost/effort to replace wire. I believe you are asking something completely different - why would I install a smaller breaker now and later upgrade to a larger one as necessary if the load grows? ishiboo clarified it earlier, bc its good practice and installing a breaker takes what...5 mins? Just like you, I cannot predict the amperage at which SWMBO's antique lamps, my antique tools, or anything else in our house will catch fire. If I have a 15 amp breaker installed and something wont burn until it hits 18....Ive just prevented myself from starting life over a bit poorer compared to the 20.
I suppose I could hard wire a few of the various 1 hp motors on my machine tools into the 50 amp welder circuit, but for my own ease of mind I think Id rather not. Paranoid? You betcha.
Not sure if you read the OP, but we know the wire is sized BEYOND the load. Thus, you size the breaker to the load, since the wire's integrity is given as being safe. No, my statement isnt true in ALL situations, but very few statements are.
I gave him the benefit of the doubt.
So... why not have 30A and 40A receptacle circuits on larger wire, with receptacles that have a higher pass-through? Because the lower you can reasonably limit the current at the breaker, the less fault current those devices can pull... thus the "safer" things are.
Thank you kindly for cutting me a bit of slack, and you read my point exactly. In the case of household wiring where you have codes and hardware differences to protect you some of this stuff is admittedly a bit redundant, but in an industrial setting, a lab, or overseas being a bit paranoid and developing safe practices is important. Cant say I will ever regret being "too safe" tho some of these internet jockeys may regret not being so.
Since you are accomplishing nothing by being a **** and missed the same things that several others did in the OP, I too will speak slowly and hopefully with a bit more clarity....
My statement that you quoted about "upgrading" referred to oversizing wire to plan for the future possibility of having a larger load, and avoiding the cost/effort to replace wire. I believe you are asking something completely different - why would I install a smaller breaker now and later upgrade to a larger one as necessary if the load grows? ishiboo clarified it earlier, bc its good practice and installing a breaker takes what...5 mins? Just like you, I cannot predict the amperage at which SWMBO's antique lamps, my antique tools, or anything else in our house will catch fire. If I have a 15 amp breaker installed and something wont burn until it hits 18....Ive just prevented myself from starting life over a bit poorer compared to the 20.
I suppose I could hard wire a few of the various 1 hp motors on my machine tools into the 50 amp welder circuit, but for my own ease of mind I think Id rather not. Paranoid? You betcha.
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Kevin C
Well-known member
FYI to get NRTL approval with a device designed to plug into a 15 or 20 amp circuit, you need to demonstrate that your devices ground circuit can shunt a fault current of 40 amps for two minutes. This is to assure that a 20 amp breaker will trip before the device catches fire.
Short answer... Breaker is size is considered with regards to the devices that are plugged into a circuit.
If a device develops a short it must be capable of tripping the breaker without overheating the ground circuit.
This is an OHSA requirement. Its not directly stated, but the rules make it work out that way.
That is the part of where the sizing the breaker to the load comes into play. That is why you don't want to put devices designed for 15 or 20 amp circuits onto circuits that can deliver a much higher current ( 40 amp breaker that trips at a much higher current on short term overloads).
Yes, the first thing a breaker does is protect the wires in the wall. However, whats plugged into it is designed to be able to trip the breaker without over heating and creating a fire hazard. So if you see a UL or equivalent sticker on a device and it has a three prong plug, I will guarantee you that it was designed and tested to be capable of tripping a 20 amp breaker ( or 2x the rated current, what ever is greater).
I'm not up on the standards for double insulated, non grounded equipment.
As far as I know, you wont see this in any section of the NEC. You will see it in other standards that are part of certifying devices that are connected to mains.
What is an NTRL? NTRL's (nationally recognized test labs), certify products for the US market ( UL is a NTRL).
http://www.osha.gov/dts/otpca/nrtl/
Typical Certification Marks
http://www.osha.gov/dts/otpca/nrtl/nrtlmrk.html
Getting that cert is no small deal. The list of tests needed to assure safety is huge. Right now I am working with IEC / UL 61010-1. Buried in there are tests to show that the housing is rigid enough to prevent fire or shock after impact damage, heat damage dropping, internal shorts, blocked vents, jammed motors and so on.
The 40 amp tests is part of the north american version and requires the ground system be able to conduct a minimum of 40 amps from all possible fault points for two minutes ( or 2x the rated current).
EDIT: In short (pun intended), anything you can plug into a 15 amp circuit is designed do be able to clear a breaker on a 20 amp circuit (inferred by how US code is written). If you got creative and had a 120 v 30 or 40 amp circuit, the ground system of a device designed for normal 120v circuits may not be able to trip that large a breaker if the system had a short.
If your plugging in devices that don't have a NTRL stamp (UL, CSA. TUV ect) then its pretty hard to predict what would happen. Always a good idea to buy tools, heaters or whatever that have been tested.
Short answer... Breaker is size is considered with regards to the devices that are plugged into a circuit.
If a device develops a short it must be capable of tripping the breaker without overheating the ground circuit.
This is an OHSA requirement. Its not directly stated, but the rules make it work out that way.
That is the part of where the sizing the breaker to the load comes into play. That is why you don't want to put devices designed for 15 or 20 amp circuits onto circuits that can deliver a much higher current ( 40 amp breaker that trips at a much higher current on short term overloads).
Yes, the first thing a breaker does is protect the wires in the wall. However, whats plugged into it is designed to be able to trip the breaker without over heating and creating a fire hazard. So if you see a UL or equivalent sticker on a device and it has a three prong plug, I will guarantee you that it was designed and tested to be capable of tripping a 20 amp breaker ( or 2x the rated current, what ever is greater).
I'm not up on the standards for double insulated, non grounded equipment.
As far as I know, you wont see this in any section of the NEC. You will see it in other standards that are part of certifying devices that are connected to mains.
What is an NTRL? NTRL's (nationally recognized test labs), certify products for the US market ( UL is a NTRL).
http://www.osha.gov/dts/otpca/nrtl/
Typical Certification Marks
http://www.osha.gov/dts/otpca/nrtl/nrtlmrk.html
Getting that cert is no small deal. The list of tests needed to assure safety is huge. Right now I am working with IEC / UL 61010-1. Buried in there are tests to show that the housing is rigid enough to prevent fire or shock after impact damage, heat damage dropping, internal shorts, blocked vents, jammed motors and so on.
The 40 amp tests is part of the north american version and requires the ground system be able to conduct a minimum of 40 amps from all possible fault points for two minutes ( or 2x the rated current).
EDIT: In short (pun intended), anything you can plug into a 15 amp circuit is designed do be able to clear a breaker on a 20 amp circuit (inferred by how US code is written). If you got creative and had a 120 v 30 or 40 amp circuit, the ground system of a device designed for normal 120v circuits may not be able to trip that large a breaker if the system had a short.
If your plugging in devices that don't have a NTRL stamp (UL, CSA. TUV ect) then its pretty hard to predict what would happen. Always a good idea to buy tools, heaters or whatever that have been tested.
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Speedy Petey
Well-known member
Good practice??? Are you kidding me?
First and foremost, the breaker protects the wire, NOT the connected load. A 15A breaker will NOT prevent a fire compared to a 20. That is simply wrong.
HOW is something supposed to "catch fire" at 18A but not 15 or 20?
Your argument makes no sense and holds NO water.
Also, are aware of the ACTUAL amperage ratings of #14 and #12? 15 and 20A breakers are ALREADY undersized compared to the actual ratings. 240.4(D) is the only reason we are limited to 15 & 20A breakers respectively.