For straight pulls, 314.28(A)(1) requires that the length of the box be at least eight times the trade size of the largest raceway. To correctly apply 314.28(A)(1), just multiply the largest raceway size by eight. The box must be at least as long as that number.

Allowable Conduit Fill Capacities

Trade Size

Look up the area of each conductor size in the tables, multiply by the number of conductors, add them for a total, multiply by 5 (5 x 20% fill) and then you have the minimum cross sectional area of your wireway.

The depth of a box for a straight pull is determined by the size of the largest conduit and by space required by locknuts and bushings. On the other hand, the pull box length must be at least eight times the diameter of the largest conduit: Assume a pull box has four conduit runs, and the largest diameter is 4”

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

32 inches

You can go as many feet as you want.. the code only restricts the number of bends between boxes or fittings like a LB to (360) degrees..

As a rule of thumb, pull boxes are used when conductors are pulled straight through a box and terminated down-stream. On the other hand, junction boxes can be used for splicing or tapping conductors. Larger boxes provide more capacity, and they make pulling, splicing, tapping or positioning the conductors easier.

For example, a pull box contains two conduits located on opposite walls. While one conduit has a trade size of 2 inches, the other has a trade size of 3 inches. The minimum length of this box is the trade size of the largest raceway (3 inches) multiplied by eight.

Since the conductors are without splice or termination, only six conductors are counted. 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.

How to Calculate Underground Pull Box Sizing

1. (Largest Raceway Size x 6) + Sizes of Raceways on the Same Row = Minimum Box Length.
2. For example, if you have a row with 3-3” raceways, and another row with 3-1” raceways:
3. Largest Raceway Size x 6 = Minimum Distance Between Raceways.

Re: Stacked Junction boxes Yes, as long as the wire fill meets code, and you have the required length of wire extending from the front of the extension ring.

You can stack as many as you like, as long as you meet 300.14.

To join two or more gangable boxes together, you’ll first need to remove the set screw from the side of the box that will be joined to an adjacent box. These set screws hold the removable side plates in place. Set the screws aside, because you will need them again to connect the boxes together.

Personal preferences: Device boxes are available either gangable or non-gangable. Gangable means that two or more boxes can be joined together, on the job site, to create a multi-gang box as required. Most boxes are also available with or without brackets.

Metal cable and conduit depend on the contact from its metal sheathing to the metal box to complete grounding. Even if the device does not complete the ground, Romex or NM wiring can always be used with metal electrical boxes by attaching the bare or green grounding wire to the box by a screw.

Because they are plastic, there is no need to attach a ground wire to it. Since it is made of a non-conductive material, switches and outlets cannot short out if they touch the side of the box. Plastic boxes usually come with tapped screw holes for easy attachment of switches and outlets.

Going without a ground wire When you screw the light switch in, it will make contact with the box, and as long as the box is grounded, it will pick up ground that way. If the box isn’t grounded, the switch will still work.

The appliance will operate normally without the ground wire because it is not a part of the conducting path which supplies electricity to the appliance. In the absence of the ground wire, shock hazard conditions will often not cause the breaker to trip unless the circuit has a ground fault interrupter in it.

If you are replacing a switch a ground is not required, as per the above exception. However, if you’re installing a switch; replacement or otherwise, into a metal box that is grounded. The switch will be ground via the devices yoke and mounting screws. So if the metal box is grounded, the switch is also grounded.

The short answer is: no, they don’t need to be grounded, but it is way safer if they are. Many, if not all, electrical codes require installed light fixtures of all types to be grounded. LED fixtures come in two types, 12V and 120/240V types.

If it’s a single pole switch with two terminals, the answer is no. One wire is the power to the switch and the other wire goes to the light. The black wire (hot) is switched so both black wires are connected to the switch. The switch may have gold and silver colored screws.

Self grounding means the switch must be installed in a METAL box that is grounded. The switch has a clip that will ground it to the metal box if you do not want to use the grounding screw. The screw is to use if installing in a pvc/ plastic box.

But here’s the catch: If you connect the circuit wires to the wrong terminals on an outlet, the outlet will still work but the polarity will be backward. When this happens, a lamp, for example, will have its bulb socket sleeve energized rather than the little tab inside the socket.