Why do we calculate box fill?

Part (B), “Box Fill Calculations,” describes the method for determining how much volume (fill) may be occupied by conductors, clamps, support fittings, devices (switches or receptacles) or equipment, and equipment grounding conductors.

How many #12 wires are in a 4 square deep box?





nine 12 AWG

Table 314.16(A) permits a maximum of nine 12 AWG conductors in a 4-inch square box that is 1 1/2 inches deep. This installation is Code compliant.

How do you count the number of wires in an electrical box?

Each item in an electrical box counts as a different number of wires. Each insulated wire, all cable clamps combined, all uninsulated wires combined, and each support for light or another fixture count as one wire. Each switch, outlet, or other device counts as two wires.

What is box fill in Electrical?

Box fill isn’t just the number of wires in the box — it’s the total volume of the conductors, devices, and fittings in a box. Every outlet box has a specific amount of space for conductors, devices, and fittings.

How do you calculate volume of a box?





To find the volume of a box, simply multiply length, width, and height — and you’re good to go! For example, if a box is 5×7×2 cm, then the volume of a box is 70 cubic centimeters. For dimensions that are relatively small whole numbers, calculating volume by hand is easy.

Do you count ground wire in box fill?

314.16(B)(5) Equipment-Grounding Conductor Fill



Equipment-grounding conductors and equipment-bonding conductors are not counted the same as other conductors. Each grounded (neutral) conductor and each ungrounded (hot) conductor, originating outside the box and terminating inside the box, counts as one conductor.

How many wires can be connected in a box?

For example, the smallest 2-by-4-by-1-1/2-inch-deep box can comfortably splice only two cables (four or five conducting wires), while the largest 4-by-4-by-2-1/8-inch-deep boxes can handle as many as four to six cables (up to 18 individual conducting wires).

How many 14 2 wires can you put in a receptacle box?

Plastic Box Fill Capacities



Single Gang Boxes: A total capacity of 18 cubic inches allows for nine #14 gauge wires, eight #12 gauge wires, or seven #10 gauge wires. This is a wires-only capacity. With one device added to the box, subtract two wires in each category.

What is a 1900 box?



A 1900 Electrical Box is defined as a standard 4 inches (4”) square electrical switch box which is the combination of a gas and electrical box. It is the most commonly used box when a simple switch box is not big enough.

What is an 8b box?

4″ octagon outlet box 1-1/2″ deep or 2-1/8″ deep and varying K/O sizes.

What is a 2100 box?

Top Definition



This electrical box is slightly larger than the standard 1900 or 4″ box. Called a 5″ box because of its 4-11/16″ size, it is used for a wide variety of applications where heaver cables are needed or bulky wiring devices require a higher volume box.