I need to replace existing wiring in a bedroom/office. The panel is located in a basement and NM can be run up a chase to the attic. From the attic, access to receptacle locations can be made through the wall plates down to the receptacle locations. The question concerns cable length and the best way to avoid voltage drop.

The cable distance from the panel to the attic is about 20 feet. If the cable travels in series to each of the five receptacle locations, it will require an additional run of about 110 feet for a total run of about 130 feet. This is figured by continuing the run from the basement to the plate above the first receptacle, fishing cable down to the first receptacle and back up to the attic, over to the second receptacle location, down,up and so on until all 5 locations are wired. Obviously, a splice in the wire is made at each receptacle resulting in four intermediary splices before the final outlet.

An alternative would be to run from the panel to a j-box in the attic and splice to individual branches from there to each receptacle location. Doing this would result in a maximum cable distance to any one receptacle location of no more than 50 feet. However, this would also require a j-box large enough to accommodate the feeder line and five separate branches for a total of 12 conductors in the box plus grounds. Since each receptacle would be wired independently, there would be only one splice (in the j-box) between the panel and each receptacle.

The room is currently used as an office, but technically qualifies as a bedroom. 12/2 NM connected to an AFCI in the panel will be used.

Which solution results in the best (safest, most dependable... ) wiring scheme with the least voltage drop?

Thanks for the help.

Use #10-2 cable,for one circuit, from the panel to a 6" x 6" x 4" junction box, then use #12-2 from the JB to each outlet, all on a 20 amp AFCI breaker.

If you ever want to add another circuit later, the feeder can be a #10-4 cable,with four insulated wires, so you can have two 20 amp circuits, and no shared neutral.

I can see the value in the 10/2, but is that absolutely necessary? Also, there will likely be rewiring of another bedroom (used as a bedroom). Would it make sense to use the same wiring configuration and put it on a 15 amp AFCI?

Thanks for your quick response!

If a #10 wire had a 16 amp load at 130 feet, the circuit the circuit will have a 4.2% Voltage drop, and #12 is 8%,the max recommended is 3%.

Right, but if the feeder goes to the j-box and branches from there, the length of the feeder is about 20 feet and the longest branch would be about 30 feet. The other branches would run about 20 feet from the j-box.

What happnened to the 130 feet? If the length is only 50 feet, what is your question?

My original question posed 2 wiring options. One, wiring outlets in a series without a j-box, the other using a j-box and running branches to each receptacle. Your reply indicated using 10/2 to a j-box and 12/2 from there to individual outlets. As I explained in the original question, The first scenario (a series) would require a max run of about 130 feet. In the j-box scenario, the max run to any one outlet would be about 50 feet.

OK got it. Sorry got a little confusd by your original question.

Use #10 for the 130 foot option,#12 for the 50 foot option.

Thanks a lot for your time -- sorry to have confused you. Your insight has been helpful even with my confusion. What do you think of the number two option in general - branching out from the j-box? I'm not a big fan of wire nutting 6 conductors together.

Option 2 is OK just have some large blue wirenuts on hand , twist the splice firmly ,and be sure there is no bare copper exposed after twisting the wirenuts on.