**Pull And Junction Boxes**

The requirements for sizing pull and junction boxes are in...

Article 314.28(A): For raceways containing conductors of 4 AWG or larger that are required to be insulated the enclosure dimension is to be calculated based on the diameter of entering raceways.

The purpose of calculating box dimensions (width and height) are meant prevent damage to wire insulation. But, another reason is to help prevent “bleeding knuckles” on wire pulling electricians.

Article 314.28(A): For raceways containing conductors of 4 AWG or larger that are required to be insulated the enclosure dimension is to be calculated based on the diameter of entering raceways.

The purpose of calculating box dimensions (width and height) are meant prevent damage to wire insulation. But, another reason is to help prevent “bleeding knuckles” on wire pulling electricians.

Straight Pulls

*314.28(A)(1): In straight pulls, the length of the box shall not be less than eight times the metric designator (trade size) of the largest raceway.*

In the box diagram above we have two 3” conduits on opposite sides enclosing the same group of conductors. This qualifies as a straight pull and the length of the pull box would have to be a minimum of 8 times the trade diameter of the largest raceway...

8 x 3” = 24”

Angle Pulls And U-Pulls

*314.28(A)(2): Where splices or where angle pulls or u-pulls are made, the distance between each raceway entry inside the box and the opposite wall of the box shall not be less than six times the metric designator (trade size) of the largest raceway in a row. This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box. Each row shall be calculated individually, and the single row that provides the maximum distance shall be used.*

Although they’re called angle or u-pulls we are still calculating box dimensions (width and height). It’s a bit confusing, but the code clearly states an angle or u-pull is

In the box above we have two (3" and 2”) conduits on the left. What we are looking for is the distance between the wall on the left and the wall on the right side of the box. In other words “the width” of the box. To find this dimension we must multiply the largest raceway by

*“the distance between each raceway entry inside the box and the opposite wall of the box.”*

In the box above we have two (3" and 2”) conduits on the left. What we are looking for is the distance between the wall on the left and the wall on the right side of the box. In other words “the width” of the box. To find this dimension we must multiply the largest raceway by

*“six times the trade size of the largest raceway in a row.”*(6 x 3”) = 18”

Also, we must add the other the other 2” raceway on the same wall.

*This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box...*(6 x 3”) + 2" = 20”

What about the 4” conduit on the bottom of the box. This would also be considered an angle pull even though we are determining the distance between the bottom of the box and the top of the box “the height.” Seeing as there is only one entry on the bottom of the box we would just multiply the six times 4”...

6 x 4" = 24"

So, the box in this problem would be 20” wide by 24” high. Strange that we base the width and height of a box by calculating angle or u-pulls. But, it makes sense when we realize that when we pull and feed wire we pull from side to side, top to bottom, or bottom to top.

Conductors Enclosing The Same Raceway

314.28(A)(2): The distance between raceway entries enclosing the same conductor shall not be less than six times the metric designator (trade size) of the larger raceway.

These are the only measurements that don’t deal with the outer dimensions of a box. In the box above we have one 3” conduit and one 2” conduit on the bottom wall of the box. In order to have a proper distance between conduits enclosing the same conductors we multiply the larger (3”) conduit times six...

6 x 3” = 18”

This clearly gives enough wire pulling space so that we don’t scrape or damage the wire insulation.