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09-29-2007, 01:57 AM   #1
Newbie

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I'm converting my attic into a bedroom and about to ad a 20 amp breaker to my box using 12/2 wire

The question that i can't find the answer to is how much is ok to put on this new circuit

right now I'm planning to put - 2 light fixtures (both with one bulb that i will be using the 13 watt fluorescent bulbs in) and 3 to 4 outlets

the outlets won't be used for anything major (typical bedroom stuff)

is this ok or is it too much??

if some one could give me the rated watts of a 15 amp and a 20 amp circuit that would be great

thanks

09-29-2007, 05:44 AM   #2
Electrician philosopher

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The short answer is the twentyA circuit is plenty. In commercial applications the code tells us that you allow 180VA(watts) per receptacle. Using Ohms Law: I=P/E allows us 13 receptacles for 20A circuit. In a dwelling unit it falls under general lighting loads at 3VA per sq./ft. But..... thats only for calculating the service. There are no restrictions(In the USA, Canada is different!) on the number of outlets on a circuit. All that being said, ytou are in good shape with what you have and could actually downsize it to 14/2 and 15A breaker

Edit to add: Using Ohm's Law p=e*i 20A=2400W 15A=1800W

Last edited by Andy in ATL; 09-29-2007 at 05:48 AM.

 09-29-2007, 09:15 AM #3 Member   Join Date: Jul 2007 Posts: 308 Rewards Points: 250 My opinion only: I would put the lighting on a different circuit than the receptacles, or split the receptacles and lighting between two circuits, regardless of the branch size. The reason for my thinking is that if the breaker trips, you don't want to throw the entire room out. That said, it would be a total waste to bring up a second branch just for this purpose. Perhaps you could use an existing circuit already available in the attic for the lighting. FW

 09-29-2007, 11:11 AM #4 Member   Join Date: Jun 2007 Posts: 3,709 Rewards Points: 78 I like to keep lighting and receptacles seperate, but in this situation one 20 amp circuit would be fine. You could use 15 amp, but why? You have to run the wire anyway. Use 12/2 and 20 amp breaker. No limit on recepts either. I like the idea of using an existing lighting circuit for upstairs if possible. Its nice to have lights when installing the recepts...lol Don't concern yourself with watts. You can add up the lamp watts, but you can't determin watts on recepts without knowing what your plugging in.
 09-29-2007, 11:39 AM #5 Electrician philosopher   Join Date: Aug 2007 Location: Lilburn, GA Posts: 838 Rewards Points: 500 Don't concern yourself with watts. You can add up the lamp watts, but you can't determin watts on recepts without knowing what your plugging in.[/quote] Nor should you worry about it! Even though you are the homeowner you are also the new head electrician on this job! The fact is, on any given circuit you can plug in 15 hairdryers and force the breaker to trip. As far as seperating lights and receptacles, that is up to the head electrician (you). If I had extra money I would consider running 15A for my lights and 20A for the recps. That being said, as a real "head electrician" if it was my house i'd run 15A and call it good.
 09-29-2007, 04:19 PM #7 Electrician philosopher   Join Date: Aug 2007 Location: Lilburn, GA Posts: 838 Rewards Points: 500 Stubbie, why only 16A? I didn't really think anything in a house was considered continous load.
 09-29-2007, 04:40 PM #8 UAW SKILLED TRADES     Join Date: Jan 2007 Location: Kansas Posts: 5,341 Rewards Points: 2,652 Andy There is no requirement for 16 amps on the total circuit. I see where I was rather confusing in my sentence structure . What I was trying (not so good) to say was that you should not plug anything into one outlet that is over 16 amps. I agree... I did a poor job of using my own words to explain NEC 210.21(b)(2). Sorry Andy.... sometimes I get to typing away and I make a goof now and again. Good catch though just the same. Stubbie __________________ " One nice thing about the NEC articles ... you have lots of choices" Stubbie
09-29-2007, 07:47 PM   #9
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Thanks guys this has been a lot of help

and the reason that i don't split up the lights and the outlets is because the wiring in this old house is a mess - the north side of the room is already powered by one circuit and the south side by another

i wish i could just redo the hole room but there are parts that i couldn't get to unless i ripped everything out

again thanks to everybody who responded its a big help

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