/diy/ - Do It Yourself

>>1742935
You will increase the voltage drop using higher gauge wire. Resistance goes up as cross sectional area goes down. You are giving the current a smaller path to go through, increasing the charge density.

>>1742949

If I start out at 10 gauge for 50 ft the voltage drop would be 2 volts leaving 118 . Then at the splice for 12 gauge it would start out at 118 right? so If i ran that about 20 ft from the 12 gauge it would stay under 3% drop for the total would that work right?

>>1742955

Jesus fucking Christ. Learn Ohm's law (first week of any EE babby course) before you do anything electrical.

Goddamn. V = IR. If you can't handle that, give up.

>>1742949
The more you know

>>1742955
Yes, that’s the way to figure this one.
Cheers!

To save what, $8.00?

You'll spend that on the junction.

>>1742935
Yes. You're on the right track with this. Technically you only need to use 12ga here since the Vdrop is still under 5%, but using 10ga for the straight run back to where the circuit branches out (outlets or whatever) will be more efficient (less loss in the run) and will give you more power at the end point. Run the 10ga for as long as it's practical for the lowest drop. It's the size where splicing starts to become a pain in the ass, so minimize the junctions along your run and pay attention to get your splices nice. A bad splice can easily add more resistance than you removed by using 10ga.

>>1742955
Your use of the website works, but the best way to model this is as a total of resistances. 10ga copper is 0.9989 ohm per thousand feet. 12ga is 1.588 ohm per thousand feet. If you add (round trip) 100' of 10ga and 40' of 12ga that gives you 163.4 milliohms, which at 20A is 3.268Vdrop (E=IR), so 116.73V at the load.

>>1742935

Yes. This is the basic idea behind a breaker box (you have massive wires going in for the "long haul" and then 14 gauge wires to fan out to the individual circuits.

In fact, this is probably what you should do, you shouldn't have any concealed connections inside walls or anything.

Just make sure you DO NOT put a 30 A breaker in there at the source. Use a 15 A breaker since you are using the 10 GA wire just to lower the voltage drop, the ultimate current carrying capacity will still be the 12 GA wire (which could overheat at 30 A).

>>1743185
>you shouldn't have any concealed connections inside walls or anything.
Good point. Usually the heavier gauge wire will terminate in an exposed junction box in a basement/attic/wherever, or at the first outlet/switch, as long as the maximum capacity of the box with the larger wire is accounted for. You don't need a subpanel or anything, but junction boxes are required to be accessible.
>Use a 15 A breaker
12ga can carry a 20A branch circuit by national code in the US.

>>1743313
>12ga can carry a 20A branch circuit by national code in the US.
Cant use more than 80% of what the breaker (and I think wire too) is rated for. But yeah he could get away with a 20A so he can draw 15A without tripping anything.

>>1743346
The circuit capacity isn't defined by the continuous load limit of the breaker, but the intermittent rating. You don't go and buy a 12.5A breaker. You buy a 15A one. You look up 15A in your NEC book and find 14ga specified. You don't have to derate anything unless you're running lots of wires in a conduit or are otherwise expecting a high ambient temperature.
You can for sure draw 20A on a 20A circuit. You can draw that for several minutes in most cases, and might even be able to draw it for ten minutes or more depending on the ambient temp. You can even draw 40-60A out of most 20A breakers for a few seconds. This behavior is required to prevent nuisance tripping when motors kick on. The absolute instant-trip limit of a breaker depends on the design, but it's usually around 10x the intermittent rating. After that the trip time is measures in single digit milliseconds or microseconds.

>>1743157

thanks for showing how the calculation is done.

>>1743185
>>1743313
>>1743346
>>1743381

The Splice will be done in the attic in a junction box and I will label the wires in my Circuit breaker panel with tape as 20amp max and use a 20amp breaker thanks all.

>>1742969
That's Kirchhoff's law dude

>>1743917
Like he said, you will loose any benefit of the bigger wire size by having a junction since you will probably just use marettes like everyone else does. 100ft is fine for 12ga if it means you avoid junctions

also, that calculation is slightly wrong. just to be technical, you use impedance on AC circuits, not resistance. all the added capacitance in the circuit effectively lowers the resistance

tl;dr just do it all in 12ga, save yourself the additional cost of 10ga and remove a junction

>>1745966
>V = IR
I=current
R=total resistance of all wires, so R=R12+R10 where R10 is one wire and R12 is the second
V=Voltage drop

idk if that was a bait or not but...

>>1746065
Well yea, if you look at it that way, but Kirchoffs second law is about sum of voltage drops in closed loop. Anyway, pretty basic stuff.

>>1746004

I'm using the 30Amp Wago connectors.

>>1746463

I twist, solder, marette, and tape per each connection. But that's just me.

It's also a good idea to put a 2000 w heater on the end of the outlet, and run a flir infrared camera over the wiring and connections to check for any hot spots.