15 &20 amp breakers
- Thread starter rcollins
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- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
There are at least two conflicting viewpoints on this question. Mine is that the code does not give a limit. Those who think otherwise are likely to ask you whether or not you are talking about a dwelling unit.
claytazdaisy
Member
it wont be how many Switches can be on a circuit. its how many lights and the watts that the lights use. what is the max you use on a circuit? 85% right? if it is a 15amp 120volt circuit you have 1800watts and 2400watts on a 20amp. if your talkin 277volt 15amp you got 4155watts and 20amp you have 5540watts available. basic electrician math. just count your circuit out just like an engineer would. its not in the code though. the 85% is. somewhere. cant find it. could be 80%
if i understood the question correctly. lol
if i understood the question correctly. lol
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No, you can load a circuit to 100% for up to 179 minutes 59 seconds.
It would be 80% for continuous loading.
Roger
claytazdaisy
Member
you got the timing down huh. wow.
why only that long
why only that long
brian john
Senior Member
- Location
- Leesburg, VA
Little thing called the NEC and continuous loads Article 100 Definitions
claytazdaisy
Member
sooo. i grabbed my code book and scanned through article 100. all 7 1/2 pages. didnt see anything under continuous loads that amounted to 179 m and however many seconds. howd you come up with the number
claytazdaisy
Member
even dont see anything in 210.19
Article 100
Continuous Load.
A load where the maximum current is expected to continue for 3 hours or more.
3 hours x 60 = 180 minutes
180 minutes - 1 second = 179 minuites and 59 seconds
Not a continuous load
:grin:
claytazdaisy
Member
well, yess. thats a continuous load calculated at 125%. so if you lighting load is 1000watts, and its figured to run continuously you count it at 1250watts. i was stating that you never cram pack your circuit to 100%. only count it to 85%. or 80% what ever it is in the code. its not in article 100. and in the definition of continuous load it says nothing about a time limit running a circuit at 100%( 20amps out of 20amps)
claytazdaisy
Member
i think the 85% is just the way i was taught. 220.18 says total load shall not exeed the rating of branch circuit. no time limit though
It doesn't have to say anything about a time limit, if it's less than 180 minutes it's not a "continuous load", so the definition of "continuous load" doesn't come into play.
Roger
claytazdaisy
Member
dont understand why you said it like that.
1 more second wont make your load jump to 125%. and if you count out your circuit to 100% with a countinuous load. 125% rule should be accounted for.
i was just stating that i was taught to only count my circuits to 85% with everything applicable accounted for. Thats so when your pulling a full load on the circuit and you plug in a vaccum you dont trip a breaker. In residential some bosses are cheap and like to run 15 amp circuits to rooms to cover lighting and recepts. I like to run 15 amp lighting only circuits and 20 amp recept only circuits. Thats so when you plug your vac in the lights dont even dim.
so back to the original question. its not how many switches and boxes you can put on the circuit. its the wattage that the lights and devices use that have to be accounted for
mivey
Senior Member
Because that's the way the code is written
No it won't change the load but it does change it to a continuous Load.
Now we're getting on the same page. :wink:
Not saying that is not good practice but, many rules of thumb and myths dye hard sometimes
If you have a fully loaded circuit and plug a vacuum in it better trip and that has nothing to do with being continuous or non continuous.
I don't think it is being cheap if a 15 amp circuit is all that is needed, some people are happy with a Kia and that is all they need while others want Cadillacs
Agreed.
Roger
- Location
- Massachusetts
surf more
Senior Member
- Location
- eastern NC
funny--had this talk at work a couple days ago---cost--
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
That's the one thing you've said that I agree with. :smile:
But, the NEC does back up what the other guys are telling you.
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