12.8 amps too much for 15 amp circuit?? how to install new circuit?

[rives]

Section 215.3 of the NEC stipulates that the OCPD (that would be the breaker) needs to be sized at 125% of the continuous load, which means that they are expected to carry continuously 80% of their rated (nameplate) current.

MDS, you have a dangerous installation, regardless of your comfort level with it. You can do as you like, but the people on here need to be guided to conservative, safe installations.

 

[Bullfrog44]

Section 215.3 of the NEC stipulates that the OCPD (that would be the breaker) needs to be sized at 125% of the continuous load, which means that they are expected to carry continuously 80% of their rated (nameplate) current.

Great info, however does that mean that you don't have to take 80% of your total wire load? Common sense would say yes, but I believe the code says something to the effect of "shall not" exceed 80%. I need my code book, I will bring it home from work tomorrow. Is there an online source for the NEC book?

Edit: what year book are you getting that from?

 

[rives]

Great info, however does that mean that you don't have to take 80% of your total wire load? Common sense would say yes, but I believe the code says something to the effect of "shall not" exceed 80%. I need my code book, I will bring it home from work tomorrow. Is there an online source for the NEC book?

Edit: what year book are you getting that from?

I just Googled it - I'm on the road and don't have a code book with me, but the information was supposed to be from the 2008 book. If I remember correctly, a "continuous load" is a load that exists for 3 hours or more. If I am interpreting it correctly, shorter duration draws exceeding the 80% are allowable.

 

[irobot sd]

you are right anything over 3 hours is 125% of rated amperage.
example an air conditioner pulling 12 amps sounds ok for a 15 amp breaker right? Well if you plan to run it for 10 hours a day that would be a continuous load. 12 amp x 125% = 15 amps. so you would want the next size breaker 20 amp. I think the max watts you would want to run is 1440 for a 15 amp breaker. its always better to play it safe and leave room on the load

 

[Bullfrog44]

I just Googled it - I'm on the road and don't have a code book with me, but the information was supposed to be from the 2008 book. If I remember correctly, a "continuous load" is a load that exists for 3 hours or more. If I am interpreting it correctly, shorter duration draws exceeding the 80% are allowable.

Yea.....but that says nothing about breakers covering the 80% rule. I am still not convinced.

 

[rives]

Yea.....but that says nothing about breakers covering the 80% rule. I am still not convinced.

I'm not sure that I understand your question - could you restate it?

 

[supersmallgiant]

Also instead of running all of those floros why not just get a 600 and call it a day at 4.5 amps but more lumens

What 600w ballast only draws 4.5a? I thought galaxy ballasts were the lowest a 5a and most other digitals were in the 5.1-5.4a range with magnetics even higher than that.

 

[Marquis de Sod]

14 ga wire is rated at 20 amps. 20x80% is 16, so forcing the world to put 14g wire on a 15A breaker BUILDS IN YOUR DERATING for a continuous load. that is all i am saying. the code has "derated" this wire to allow for such things as this, as well as the obvious FACT that almost all of your wiring is run in your attic, which has a hi ambient temp. So it IS possible, that if your attic is hotter than hell AND you are running a continuous load, that if you get up there with a thermometer, and you derate your wire accordingly AND you want to run a load longer than 3 hours THAT YOU WILL HAVE TO derate the ckt accordingly. and how will you do that??? well you can either unload it or go find and special order a 10 amp breaker to put on your 14g wire.

FOR THE MOST PART you are fine to run 15 amps on a 15 A breaker all day long.

and, the FACT that you guys have found breakers that don't trip, isn't part of the equation, as there are alot of crap breakers out there, which is why i said to check your draw with an ammeter. no biggie.

i am just sick and tired of people here saying you have to derate 14g wire starting at 15 amps. that is not correct. if you want to derate the circuit because you have 60 degree C terminals on your equipment that is also a different story.

also if you HAVE to derate due to Ambient Temps, over filling a conduit, AND a continuous load, go for it. I NEVER said you NEVER have to derate 14g wire lower than 15A! there are plenty of circumstances to do it. but in a house, it's already done for you as far as most loading goes.

if your wire goes on the roof or attic and it's 100 degrees, then that needs to be derated. if your pipe has 9 wires in it, then it's only good for one half of 20. and all these things add up. see the bottom of 310-15B

but you just can't automatically use 15 amps as your starting point for derating and say that you can only run 12.

your 15A breaker is supposed to trip at 15Amps, so that is why i said up there you can run 14.9A, so that you dont cause the breaker that is working right to trip.

as for my insurance company paying for a fire caused by my 25A breaker? if it went to a non motor, non continuous load they would have to pay. but they are going to find a bunch of fried ballasts and pot plants, so.....aint happnin anyway.

PS, i am looking at the 2011 handbook, but the table is the same except they changed the number from 310.16 to 310.15B16. now THAT is something I CANT explain.

 

[rives]

14 ga wire is rated at 20 amps. 20x80% is 16, so forcing the world to put 14g wire on a 15A breaker BUILDS IN YOUR DERATING for a continuous load. that is all i am saying. the code has "derated" this wire to allow for such things as this

You are looking at it from the wrong perspective. The breaker is what is being derated to 80%(if it is a "continuous" load and if the breaker is not listed for 100% duty. Best rule of thumb? Use 80% of the breaker capacity). Once again, check NEC 215.3.

 

[Bullfrog44]

Even though it says the breaker is rated 125%, does that mean you don't have to follow the 80% rule when rating wire gauge? I hope I asked that better this time....

 

[rives]

Even though it says the breaker is rated 125%, does that mean you don't have to follow the 80% rule when rating wire gauge? I hope I asked that better this time....

As far as I can recall, the only conductor/current adjustments necessary beyond the fine print notes for 310.16 that stipulate the maximum amperages to be:14 ga - 15 amps, 12 ga - 20 amps, and 10 ga - 30 amps, are to compensate for anticipated voltage drops on long runs, multiple conductors in a raceway, motor starting current (125% of full load current) and temperature. I believe that the 80% rule (or 125% depending on which way you are working the math - they are basically the same thing) is for the circuit protection (breaker or fuse). If anyone has a different interpretation, I'd like to hear it.

 

[Marquis de Sod]

i never thought of having to protect a breaker. i cant give you any support for my belief tho.. to me the breaker is the protection.
and i dont know how to answer your question Bullfrog, other than to say that what determines the ampacity of the circuit is the size of the overcurrent protection device, not the wire. so if you have a 15A breaker on 10g wire it is considered a 15A circuit. you may have that small breaker on the bigger wire for a reason, v drop or maybe any of the reasons that rives said above, or maybe somebody down the line tapped into that 10g with a piece of 14g, in which case they had to put a smaller breaker on there to protect that: the weakest link. (dont do that either).

sorry i even brought this crap up. i reallllllly HATE giving ANY elec advice to home owners. give them an inch and they will take a mile, and do it wrong anyway. it is one reason i quit the BH&G elec forum; i prefer that NO home owners do ANY elec work. most of you out there dont want to risk an electrode telling the cops what you are doing so feel you have no choice tho. you should all get a licesened elec. contractor to do all you work. if you tell them you are an Orchid freak or growing your own herbs, they will not even ask you squat, and if they do tell them to STFU or you will fire them.
even so, i think i will just stay the fuck out of this forum from now on.

NO i am not trying to get people to circumvent the code either. you all are WAY better off to run less current than to try to stretch it to the limits as i have. but i will leave you all with this thought: have you ever seen a panel where it told you not to run a full load for more than three hours? or bought an appliance that warned you not to use it for more than three hours? no, and i have personally measured those new Electric fire places that imitate a real fire (without the fire) because of the customer complaining it tripped her breaker, and found that she had it plugged into a 15A circuit and the SOB "fireplace" was drawing 14.8 amps all by itself!! again, this would run all day if there was nothing else turned on in that circuit, but because there was, it tripped the breaker. btw dont reset a breaker more than three times in succession.

 

[Bullfrog44]

Never mind, I guess I can't articulate my question. Later guys.

 

[budman678]

this is a good discussion