Am i thinking of this right?

[bluedude2288]

I just built an ssr box, in the box I have 16 channels, 4 boards with 4 channels a piece, I am using 14gauge wire inside my box, I have all the commons from all 16 outlets tied to one 14 gauge wire, now if i calculate right, i am only going to have at max two 100 mini lights per channel, so .33 Amps * 2per channel = .66Amps per channel,( .66Amps per channel * 16 channels = 10.56Amps), so if im looking at this correct, the total load on that wire would be 10.56Amps, so i should be ok tieing all the outlets to one common, right?

Ps: I am just worrying about the wiring inside the box which is like 2 feet long at max, I will have a large grade connecting the box to the powers supply for the long run

PSS: I bought the reel of wire from home depot, the kind that is single wire on a black reel, it says its 14AWG, but to me it seems, kinda small, is there different ratings for different types of wire?

[xmus]

You should be fine
http://www.planetchristmas.com/WireSize.htm
14ga can run up to 15A less than 25 feet.

[xmus]

but to me it seems, kinda small
Do you have a way to measure it accurately? There are tons of gauge to diameter charts online. Own a micrometer?

[bluedude2288]

Nah i dont have a way to measure it, how would i? The 14awg is printed on the jacket of it so i assumed it was correct

[xmus]

Nah i dont have a way to measure it, how would i? The 14awg is printed on the jacket of it so i assumed it was correct

It probably is correct, but the only way to double check it, would be to measure the dia of the wire and compare it to the charts online.

[Macrosill]

You should be fine
http://www.planetchristmas.com/WireSize.htm
14ga can run up to 15A less than 25 feet.

The charts referenced above are somewhat misleading. You can safely run 15amps on 14awg conductors on longer runs than 25 feet. Actually if you look at the NEC 14 awg conductors have an ampacity of 20 amps but there is an 80 percent derating factor on all "allowable" ampacities. So thats why 14 awg conductors are used for a 15 amp circuit. 12 awg can handle 25 amps but is derated to 20 amps. There are other factors to take into account, like voltage drop. Voltage drop does not become a realistic issue until you get well over 100 feet of conductor length and another important factor to consider is whether is is a single feed 110v circuit or a 220v circuit with 2 hot legs. There are too many factors to take into account to come up with a reliable chart as an end all solution for every situation. This chart is way off base. It takes into account a voltage drop of less than .5%, yes less than 1/2 percent when the allowable voltage drop as stated in the NEC can be up to 5 percent, more than 10 times higher than the percentage used to come up with that chart.

Now take a standard circuit in your house. All lighting circuits are on 15 amp circuits because that is what the fixtures are rated for. I know my house has lights more than 25 feet away from the electric panel. The chart also states for a 35-50 amp load at a distance of 10 feet you would need 8 awg. I know my electric range is more than 10 feet from the electric panel.

I would hate to see someone run 4 awg conductors to bring 20 amps to a relay that is 28 feet away from the electric panel. I think I have 4 awg feeders are used in most older instances around here for power distribution, pole to pole and pole to house, in residential areas. Now I know this is a free air scenario but most of what we do would be considered free air as it is laying on the ground with no covering.

[xmus]

Brian, is there a power rating/AWG chart that you think is more realistic that you could point us to? I also am amazing at searching around, depending on who you ask, you get a different answer.

[NogginBoink]

Xmus,

Part of the reason you always get a different answer is that the NEC has different ratings for different applications. For instance, 14awg for 15 amps for lighting circuits, but I found when I ran wire for my welder I could use MUCH smaller wire than I thought I'd have to, because the welder has a 10% duty cycle rating.

[bluedude2288]

Thanks for the replies guys! I feel pretty confidant i will be alright!

[Macrosill]

This one is directly taken from the NEC.

http://www.lappusa.com/14030.16description.htm

[xmus]

GA 60C 75C 90C
18 .... .... 14
16 .... .... 18
14 20 â€* 20 â€* 25 â€*
12 25 â€* 25 â€* 30 â€*

So, does this mean, 18Ga should never be used for >14A, and that I should expect the temp of the wire and insulation to reach up to 90C at 14A?

And how do you adjust for lengths of wire? What if I want to run 14A for 1000feet on 18ga?

[Macrosill]

Are you being sarcastic or serious?

[xmus]

Are you being sarcastic or serious?

Totally serious. I have no idea how to interpret/understand the NEC, that is why i've been favoring the planet Christmas wire chart, I actually can look at it, and understand it :)

[Macrosill]

The temps listed are for the thermal properties of the insulations listed below them. There is no data for 18 and 16 because they are not made with those insulations. Their is a calculation known as temperature derating but it does not apply in our uses.

The wire length does not effect its amperage capacity. The voltage is effected by the wire length and it is know as voltage drop. The formula can be found online easily. As a basic explanation to counter act voltage drop over long runs you would need to use larger size wire.

[xmus]

I see, so a given gauge can handle a given current (even when horrendously long) but the down side is, the voltage at the end, may be lower than you intended/desire unless you do the calculations of ohms/feet or something.

So being completly serious here: Most folks on this site are going to be using SPT1 or another 18ga wire, from the NEC code, the only column populated is the 90C column (14A) but you said "the temp ratings don't apply to us".

Is it true to simply say that 18ga can carry a max of 14A?

[Macrosill]

yes and no
18 awg can carry 14 amps but it should be derated by 20% to find its safe ampacity. So you should not load 18 awg conductors with more than 11.2 amps.

[xmus]

yes and no
18 awg can carry 14 amps but it should be derated by 20% to find its safe ampacity. So you should not load 18 awg conductors with more than 11.2 amps.

Ok, so then, the bottom line is with the NEC chart:
use the right column, and multiply by .8 to find the ampacity for a given gauge. And for really long runs, you wont melt anything down, but you might find that the voltage at the destination is undesirable.

[Macrosill]

in a nut shell yes.

[bluedude2288]

Hey thanks fpr the help guys, i know this isnt the right section but i figured id post what you guys helped with http://s5.photobucket.com/albums/y159/bluedude2288/christmas%202007/

[Omnicef]

The temps listed are for the thermal properties of the insulations listed below them. There is no data for 18 and 16 because they are not made with those insulations. Their is a calculation known as temperature derating but it does not apply in our uses.

The wire length does not effect its amperage capacity. The voltage is effected by the wire length and it is know as voltage drop. The formula can be found online easily. As a basic explanation to counter act voltage drop over long runs you would need to use larger size wire.

Hey there!

Not to beat a dead horse but he may have misunderstood what you were trying to get across. Given the voltage drop along the distance of the conducter, the current draw on that conductor will increase by a geometric factor equal to the drop in voltage if the load demand remains constant. Or I had too much beer tonight and it was a factor of 2. But nothing is free. Less inductance, more current.