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I'd like to get some expert/nec compliant advice on my wiring layout. This week I'll be wiring the foyer, porch, living room, patio, kitchen, dining, gallery and hallway to master bedroom.

I was planning to use 10-2 for right-side of house vs. 12-2 because of distance and voltage drop from breaker panel. Would I be able to use 10-2 on a 20amp breaker? I am also think 6-3 for electric stove.

Thanks.

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    Some 20A breakers are listed for #10 and I have used 10 in the past. You May need to pigtail the devices (outlets, switches) to #12 wire unless they are listed for #10. also the box fill will need to be calculated because this is unusual inspectors really look it over critically. In one case the inspector said it could not be done because he had never seen it but it can be done. – Ed Beal Mar 7 '17 at 15:03
  • Wouldn't you drop to 12/2 at the first remote box? – isherwood Mar 7 '17 at 15:39
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    You do reduce size at the junctions to device but I did several Jobs for a very unique individual that wanted 10 at a minimum. With all the individual circuits he could have used 14 with less than 3% drop but he wanted 10 had a heck of a time with the inspection because he had never come across this had to show all the box fill calculations and prove to him it was legal before he would sign off on the first job. Oregon has a rule the inspector must cite the code to write a violation. – Ed Beal Mar 7 '17 at 19:54
  • I guess if you had 300W halogen lamps, the 3kW surge might cause a dip in other shared outlets, but more likely the user thinks heavier wire will reduce EMI effects like a bath fan timer cutouts that induce flyback voltage cannot be suppressed with thicker wires. An RF cap across the dry contact switch is all that’s needed to reduce the risetime with say a 1nF plastic X safety rated part to reduce stray EMI. Yet a 3% drop in voltage is 9% drop on power. Which is just inside 10% nominal tolerances – Tony Stewart Sunnyskyguy EE75 Sep 5 '20 at 16:37
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Unless the run is extremely long (we're talking 200 feet) or has a high sustained load you won't have any problem with 12/2. Most tools/appliances I know of are designed to work properly down to 110v. Assuming a voltage drop of 3% you are still comfortably above 110v, unless you anticipate a sustained heavy load near max capacity (20A) that will start heating up the wire more than usual.

Working with 10/2 is much more cumbersome than 12/2 in in standard receptacle boxes if you're pigtailing (parallel circuit). It's even more cumbersome when it's not necessary.

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12\2 can be run up to 400 feet on 20 amp breaker

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