![]() For each yoke or strap containing one or more devices or equipment, a double volume allowance is required for each yoke or strap.The hickey is no longer popular and has been replaced with hanger straps that are fastened to the box. A hickey is a fitting that can be described as a coupling that has threads the same size as the fixture stem and has an oval-shaped hole on one or more sides for the fixture wires to exit inside the box. A fixture stud is a fitting that mounts to the top of the box, usually inserts through the knockout of a metal box and is threaded to accommodate the fixture stem. Where one or more fixture studs or hickeys are present in the box, a single volume allowance is required to be made for each type of fitting in the box.No allowance is required for small fittings like locknuts and bushings.A calculation must be made of the cubic inch capacity that is required where conductors of different sizes are installed as in section 314.16(b) Box Fill Calculations. This number of conductors permitted in various boxes, as shown in the Table, applies only where all conductors are the same size.The minimum cubic inch capacity for each size is given along with the maximum number of conductors of sizes #18 through #6 that are permitted in the box. A “standard” box is one that is included in the Table. The NEC Table 314-16(a) covers the maximum number of conductors permitted within a standard metal box.Where practicable, an extension ring that is the same shape as the box can be installed that will add adequate space so the original box does not have to be replaced. Sometimes more conductors end up in boxes than were originally intended.The box must have a cubic-inch capacity that equals or exceeds the total of the contained items. The cubic inch area required for each wire, clamp, support fitting, device and equipment ground is added together. The total volume determines the number and size of conductors and wiring devices that are permitted to be contained in the box.Boxes described in Table 314.16(A) that have a volume larger than is designated in the table shall be permitted to have their volume marked as required by this section. ![]() ![]() Boxes 1650 cm3 (100 in.3) or less, other than those described in Table 314.16(A), and nonmetallic boxes shall be durably and legibly marked by the manufacturer with their volume.The volumes of standard boxes that are not marked with their volume shall be as given in Table 314.16(A).
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