NEC Quiz: Article 314, Part 9 Answers

by Mark Lamendola

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  1. Refer to 314.28(A). Among other things, this tells you to choose between requirements 1 and 3 and, if not a straight pull, also apply requirement 2. The fact this is a 90 degree angle means it's not a straight pull. So you must also apply requirement 2. However, this requirement has nothing to do with the box size.

    If that raceway has only those three conductors, then you can calculate the box size per requirement 3. But doing so means you permanently limit the box capacity to something less than the raceway would allow. You make it a special case, and that could be confusing for people if there's ever a need for expansion. It can also be costly to expand, as you'd need to replace the box and perhaps pull all new conductors.

    Requirement 1 means you match the box size to the raceway size. From an engineering standpoint, this is the preferred option unless there is a compelling reason to go with requirement three.

    The length of the box must be at least 8 times the metric designator (trade size) of the largest raceway. If that 2-inch EMT is the largest raceway, then you need to find out what its metric designator is. But there's no reference anywhere near 314.28 to point you to a table showing this. However, we know that Chapter 9 is full of tables. In fact, the word "Tables" is its title.

    Fortunately, Table 4 is very close to the front of Chapter 9 so we find it right away. It's this table that will tell you the metric designator for a given wiring method. This table is broken out by wiring method, shown in Chapter Three Article order. EMT (Article 358) happens to be the first one. The number you need is 53.

    Now, multiply 53 by 8, and you have the minimum length of that box: 424 mm, which is 16.7 inches.

     

  2. They have to be cabled or racked up in an approved manner [314.28(B).
     

  3. Yes. But the box must be at least 1650 sq cm (100 sq in), and you must meet the conditions of 314.28(E)(1)-(5).
     

  4. It has to be accessible without removing any part of the building. In underground circuits, a similar concept applies; it must be accessible without tearing up sidewalks, digging up finished grade, etc. [314.29].
     

  5. Yes, but in such a case they must be lined with a firmly attached insulating material that's at least 1/32 in thick and be listed for the purpose [314.41].