Q. Can the lights in a dwelling unit bathroom be on the same circuit as the bathroom receptacles?
A. Maybe. There are two options when wiring bathroom outlets in a dwelling unit:
Option 1 [210.11(C)(3)]: One 20A, 120V branch circuit must be provided for the receptacle outlets required by 210.52(D) for all dwelling unit bathrooms. This 20A bathroom receptacle circuit must not serve any other outlet, such as bathroom lighting outlets or receptacle outlets in other rooms (Fig. 1). A 15A, 125V receptacle is rated for 20A feed-through, so it can be used for this purpose [210.21(B)(3)].
Option 2 [210.11(C)(3), Exception]: A single 20A, 120V branch circuit is permitted to supply all of the outlets (including outlets for lighting and equipment) in a single bathroom, as long as no single load fastened in place is rated more than 10A [210.23(A)] (Fig. 2).