15A (14-2) circuit and 20A (12-2) circuit in the same junction box?

I have a relatively straightforward question that I have had a hard time finding an authoritative answer for.

Does the NEC permit two separate circuits of different capacity and wire gauge to share the same junction box?

Some background: I am doing a complete rewire in the bedroom of my house. There is a ceiling box that I plan to use for a track light fixture, which has 14-2 cable feeding it from a 15A lighting circuit. Due to some cable routing issues, I also want to use that ceiling box as a junction for a 20A receptacle circuit wired with 12-2 cable.

The fill capacity of the box would not be exceeded. The 14 AWG and 12 AWG wire would be on separate circuits. Neutrals between the two circuits would be separate, but all grounds would be spliced together and pigtailed to the box.

My inspector said something about requiring everything in that box to be protected by a 15A breaker, but he might have thought I was planning to tie the 12-2 and 14-2 together on the same circuit.

Any feedback is appreciated!

 

Yes it does.

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No prohibition at all as long as box fill is considered which you say is good. All grounds spliced together.

 

Thank you for the quick reply gentlemen! That was my suspicion, but wanted to verify before moving forward.

 

When two or more branch circuits share a junction box, neutrals are kept in separate bundles and grounds are all tied together even if the ampere ratings of the circuits are the same.