CABINETS, CUTOUT BOXES, & METER SOCKETS 70-293

(FPN): For protection against corrosion, see Section 300-6. (b) Strength. The design and construction of cabinets and cutout boxes shall be such as to secure ample strength and rigidity. If constructed of sheet steel, the metal thickness shall not be less than 0.053 inch (1.35 mm) uncoated. (c) Nonmetallic Cabinets. Nonmetallic cabinets shall be listed or they shall be submitted for approval prior to installation. 373-11. Spacing. The spacing within cabinets and cutout boxes shall comply with (a) through (d) below. (a) General. Spacing within cabinets and cutout boxes shall be sufficient to provide ample room for the distribution of wires and cables placed in them, and for a separation between metal parts of devices and apparatus mounted within them as follows: (1) Base. Other than at points of support, there shall be an air space of at least ¹/₁₆ inch (1.59 mm) between the base of the device and the wall of any metal cabinet or cutout box in which the device is mounted. (2) Doors. There shall be an air space of at least 1 inch (25.4 mm) between any live metal part, including live metal parts of enclosed fuses, and the door. Exception: Where the door is lined with an approved insulating material or is of a thickness of metal not less than 0.093 inches (2.36 mm) uncoated, the air space shall not be less than ¹/₂ inch (12.7 mm). (3) Live Parts. There shall be an air space of at least ½ inch (12.7 mm) between the walls, back, gutter partition, if of metal, or door of any cabinet or cutout box and the nearest exposed current-carrying part of devices mounted within the cabinet where the voltage does not exceed 250. This spacing shall be increased to at least 1 inch (25.4 mm) for voltages 251 to 600, nominal. Exception: As permitted in (2) above. (b) Switch Clearance. Cabinets and cutout boxes shall be deep enough to allow the closing of the doors when 30-ampere branch-circuit panelboard switches are in any position; when combination cutout switches are in any position; or when other single-throw switches are opened as far as their construction will permit. (c) Wiring Space. Cabinets and cutout boxes that contain devices or apparatus connected within the cabinet or box to more than eight conductors, including those of branch circuits, meter loops, feeder circuits, power I circuits, and similar circuits, but not including the supply circuit or a continuation thereof, shall have back-wiring spaces or one or more side-wiring spaces, side gutters, or wiring compartments. (d) Wiring Space - Enclosure. Side-wiring spaces, side gutters, or side-wiring compartments of cabinets and cutout boxes shall be made tight enclosures by means of covers, barriers, or partitions extending from the bases of the devices, contained in the cabinet to the door, frame, or sides of the cabinet. 70-294 NATIONAL ELECTRICAL CODE Exception: Where the enclosure contains only those conductors that are led from the cabinet at points directly opposite their terminal connections to devices within the cabinet. Partially enclosed back-wiring spaces shall be provided with covers to complete the enclosure. Wiring spaces that are required by (c) above, and that are exposed when doors are open, shall be provided with covers to complete the enclosure. Where adequate space is provided for feedthrough conductors and for splices as required in Section 373-8, Exception, additional barriers shall not be required.