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Running new circuit dedicated for Xmas lights. Merry Christmas!

Running new circuit dedicated for Xmas lights. Merry Christmas!

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  #1  
Old 12-17-05, 11:17 AM
EricT
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Running new circuit dedicated for Xmas lights. Merry Christmas!

Hi all-

Upgrading my electrical to add some outdoor outlets for the high draw of too many xmas lights. To explain-

What I have now - a house built in 1986 in arizona. Code? Yeah, we have it... now. Back then, you only needed one gfi circuit that could, and does, include bathroom outlets (in 3 baths), outdoor outlets, some garage outlets and the outlet my timer for the recirc pump on my hot water heater. Obviously, plugging a constant 15 amp pull into this setup puts it right about to the throw point on the breaker, which is 20 amp. No good. Plus, from heat/resistance of the load, the bathroom outlets in the master bath get so hot they actually warped a night-light. Aghk, not safe.

What I am up to-

Ive already installed a new 20 amp breaker with one outdoor gfi outlet, which powers my automatic sprinkler timer. Very low draw. And, I should add, I did this a year ago with alot of help from this forum, thank you DIY guys! This pull is all 12-2 romex, about 75 feet.

I just knocked out a window and put in a slider, looking to add 2 outdoor outlets and 2 light sconces outside, each on seperate switches. Then, a short run later, 3 more exterior outlets dedicated for xmas lighting.

I am planning on feeding the juice off of this 20amp breaker, mainly because I pulled the wire, I know its new and its all 12 guage, not 14. All of the pulls are under the house, nice crawlspace room there.

Im not sure when I am adding too many outlets, so let me type out here the diagram, and see if you guys think this is too much.

Breaker box with 20amp breaker - 75 foot run to outdoor GFCI outlet - 50 foot run from GFCI plug (so its in the middle and will throw everything from here) to pop out in a double wall switch. Feed is wired to two wall switches here. Switch one- runs 2 outdoor wall sconce lights, short runs on both. Switch 2 - runs 2 exterior covered outlets for the same area. At the furthest of these 2 exterior outlets, I am going to coninue the run another 30 feet or so to a set of either 2 or 3 (undecided) covered exterior outlets, at the front of the house, for xmas lights. End run at last outlet.

All cabling is 12-2 right now. The entire run would GFI off the first outdoor outlet. I can pull the light sconce feed off of existing wiring in house if need be. I want to switch all those outdoor outlets on the same switch for ease of turning on and off the xmas lights. I am also considering putting in a "timer switch" that would run them on a timer - however, I am not sure such a switch would handle the amperage. Another option - if the 12-2 and gfis would handle it, I could replace the 20amp breaker with a 30.

Thoughts, comments - any ideas welcome. I just ran the first and most difficult part of the electrical run, but ran out of cable staples! So thats it for today. I am obviously pretty comfortable adding a circuit and running cable, installing switches - but I admittedly do not know the rules of how much cable is too much, how many outlets are too many. Comment on any part of my little project if you will!

Thanks,

Eric
 
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  #2  
Old 12-17-05, 01:22 PM
A
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Originally Posted by EricT
new 20 amp breaker with one outdoor gfi outlet
This pull is all 12-2 romex, about 75 feet.

looking to add 2 outdoor outlets and 2 light sconces outside
a short run later, 3 more exterior outlets dedicated for xmas lighting.
Im not sure when I am adding too many outlets

Breaker box with 20amp breaker - 75 foot run to outdoor GFCI outlet - 50 foot run from GFCI plug (so its in the middle and will throw everything from here) to pop out in a double wall switch.
coninue the run another 30 feet or so

All cabling is 12-2 right now.
I am not sure such a switch would handle the amperage.
if the 12-2 and gfis would handle it, I could replace the 20amp breaker with a 30.
Limit your voltage drop to 3% per NEC 210-19(a). At 120 volts that is 3.6 volts. Your voltage may vary.

Examples:
1. Total distance 75+50+30 = 155 feet.
Voltage drop E = (K * I * L *2)/CMA
E = voltage drop
K = Wire gauge, 12 AWG
I = Your calculated amperage, let's say 15
L = Length, 155 feet.
CMA for 12 AWG is 6530, for 10 AWG it is 10,380, for 8 AWG = 16,510

12*15*155*2 = 55,800
divided by 6530 = 8.5 volts.

For 10 AWG:
10*15*155*2 = 46,500
divided by 10,380 = 4.47 volts

For 8 AWG:
8*15*155*2 = 37,200
divided by 16,510 = 2.25 volts

So based on those assumptions you should use 10 or 8 AWG. 10 keeps you under 5%, which is the allowable drop from the feeder, and 8 keeps you under 3%, which is the allowable drop in a branch circuit. Someone more knowledgeable would have to better explain this.

Code does not allow #12 AWG on a 30A breaker under these circumstances.

Generally speaking there is no maximum number of outlets per branch circuit.

Formulas are from Electrical Wiring Residential, 13th ed. by Ray Mullin.
 

Last edited by ArgMeMatey; 12-17-05 at 01:23 PM. Reason: Corrected NEC section number
  #3  
Old 12-17-05, 01:46 PM
EricT
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Cool.

To simplify things- there is an existing outlet right by where I want to put in the switch. I am going to slave the outdoor lighting onto that, and add the outlets on thier own run, so as to save on some of the wire run, cut down on resistance and minimize the voltage drop illustrated (so nicely, might I add) above.

Going to keep the 20amp breaker as well. So the run will be:

20amp in main panel, about 85 foot (looked in my notes for that job) to GFCI, about 50 foot to wall switch, down a few feet to outlet 1, 8 feet over is outlet 2, about 25 feet over is outlet3, 20 feet over is outlet4. All dedicated for xmas lights.

The only variable left here, is whether I can get a timer switch that will fit in the wall plate, and handle the current flowing through. But for the time being, this year, I think I will throw it on a switch, and if we want just leave my existing timers plugged in and the switch on all the time.

Thanks for the math argh- and cool nic indeed!

Eric
 
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