I've been reading the threads to get advice on a small project I am working on. I am adding 3 new outlets to the second floor of my home. Here are my questions:

1) The home run is 14 gauge wire on a 15 Amp breaker. Is there any reason to use 12 gauge wire (feeding off of the 14 gauge wire) for each outlet? Is there any reason not to? The information regarding mixing different gauges of wire seems to not be entirely consistent. The reason I ask is I have 12 gauge wire, but will need to buy 14 gauge wire if I should not mix different wire gauges.

2) Is there any reason to not splice wires together in the attic? One option I see is splicing wires for the outlets together in a junction box (or probably two junction boxes given wire box fill compliance issues) versus daisy chaining from outlet to outlet.

 

No. You are still limited to 15 amps because of the #14. Reasons not to include slightly higher unneeded cost, slightly more difficult to work with, and confusion for the next person to work on it because they may incorrectly think they can increase the breaker to 20 amp. You can if you want but slightly more wire used and again if there is a problem more difficult to troubleshoot for the next person who won't be aware of the attic J-boxes. On the positive side you won't need to open walls so no wall repair when finished.

 

Mixing wire sizes on a 15 amp circuit is not prohibited, but it isn't a good practice.

Junction boxes are often installed in an attic, but if wiring a new home I would not install them there, they'll probably end up covered with insulation and never be found again.

 

If you are adamant about the attic jbox, mount it higher up on the center of a truss so it is visible and not likely to get covered. Staple your cables up so they dont get stepped on.
Write the circuit number and what it serves on the box cover.
At the panel, write "Attic Jbox" beside the circuit number as well.
Who knows, maybe you develop memory issues and end up screwing yourself in the future and not just the next owner.

 

Thanks all for the helpful advise. I'll go with daisy chaining instead.