Article 314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures
314.24 Dimensions of Boxes.
(B) Depth of Outlet and Device Boxes with Enclosed Devices or Utilization Equipment.
(4) Conductors 12 or 10 AWG. Boxes that enclose devices or utilization equipment supplied by 12 or 10 AWG conductors shall have an internal depth that is not less than 30.2 mm (13/16 in.). Where the equipment projects rearward from the mounting plane of the box by more than 25 mm (1 in.), the box shall have a depth not less than that of the equipment plus 6 mm (1/4 in.). Where wiring enters the center portion of the rear of a box opposite to the equipment, the minimum clearance shall be increased to 13 mm (1/2 in.).
(C) Clearances for Side-Wiring Entrances. Where devices or equipment are mounted in boxes having side-wiring entries, the conductors entering from the side shall be protected as covered in (1) or (2), as follows. The term side applies to any wall of a box other than the one opposite to the opening.
(1) The rearward projection of the device or equipment shall not extend beyond the centerline of the wiring knockout or other entry.
(2) The clearance from the box wall to the installed device or equipment shall be not less than 13 mm (1/2 in.).

Material taken from the National Electric Code. is reprinted with permission from NFPA 70., 2023 edition. National Electrical Code®, Copyright 2022, National Fire Protection Association, Quincy, MA. All rights reserved.