plaster rings to increase number of conductors

#Plaster rings to increase number of conductors how to

Popejoy is a licensed electrical contractor in Sacramento, California.

Throw on a single- or double-gang plaster ring that comes flush with the drywall, and you’ve got a box that’s hard to overfill.Ĭlifford A. conduit bodies enclosing conductors 4 AWG or larger shall also comply with the provisions of 314.28. junction box solves most box-fill problems. Although smaller is cheaper, larger may avoid box-fill violations. Single-gang boxes come in three sizes, 18 cu. What’s the minimum box volume needed?Ģ conductors per 14/2 cable x 2 cables = 4 If a box contains different gauges of wire, use actual volume factors for the wires and the largest volume factor for ground wires, devices, and clamps.Ī PVC box has two 14/2 cables, one 14/3 cable, and one receptacle. Multiply the number of conductor equivalents (total from step one) by their volume factor in cubic inches (listed below)ġ4-ga. A single gang square ring will work fine for a 30amp or smaller device, and with devices that have a single yoke. The threaded holes on round rings center are 8/32, on square rings the are 6/32. Step oneĪdd up the wires and devices, A K A “conductor equivalents” (wires that start and end in the box - pigtails - aren’t counted) rt66electric said: A round ring is typically used for lighting.

#Plaster rings to increase number of conductors how to

Here’s how to figure the size box that complies with the NEC. If it’s not, you can measure the inside dimensions of the box and figure it yourself. The volume in cubic inches is usually marked inside nonmetallic boxes. This applies to all equipment grounds except for an isolated equipment ground often installed on computer circuits.Box-fill calculations are done to make sure there’s enough room in an electrical box to accommodate safely the wires, splices, cable clamps (usually none in plastic boxes) and outlets or switches that you intend to put in the box. The allowance is based on the largest equipment grounding conductor.

Where one or more equipment grounding conductors enters a box, a single volume allowance is required to be made.

If a receptacle has #12 wire connected to it, a volume allowance of 2 x 2.25 or 4.5 cubic inches must be made. For example, if a switch has #14 wire connected to it, a volume allowance of 2 x 2.0 cubic inches or 4 cubic inches is required. Each device or equipment is considered individually where more than one item is contained in the box.

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. A 4-inch square extension ring, having a depth of 1.5.

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. A plaster ring, clearly marked with a cubic-inch capacity, increases a boxs volume by that amount.

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).