314.28(A)(3) Pull and Junction Boxes and Conduit Bodies. Smaller dimensions.
Code Change Summary: New code language was added to address the minimum dimensions of conduit bodies used to make an angle pull.
Specific rules apply when making an angle pull for conductors 4 AWG and larger. Boxes for these angle pulls are sized based on the rules in 314.28(A)(2) and can sometimes be quite large in order to accommodate the minimum distance required to the opposite wall.
Often, a conduit body such as an LB is used to make the same angle pull, but in a much smaller dimension.
Some of the newer, listed conduit bodies are designed to match the same radius as a typical 90° bend in the same size raceway. Basically, it’s like having a 90° bend in a raceway with a removable cover.
According to the new code language, when using these type of listed conduit bodies, no reduction is required in the number of conductors allowed in the conduit body. Whatever the raceway is permitted to contain, the conduit body can also since the radius of the listed conduit body is no different than simply making a 90° bend in the raceway. These conduit bodies must be marked to show they have been specifically evaluated in accordance with this provision.
The last part of the new code change basically states that if the maximum number of conductors allowed in the conduit body is less than what the raceway is permitted to hold, then the conduit body must be permanently marked with the maximum number and size of conductors permitted. This eliminates situations where the raceway is filled to the maximum allowable fill and the conduit body is too short to allow the wires in it to make the 90° bend without damage to the conductor insulation.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2011 Code language:
314.28(A)(3) Smaller Dimensions. Boxes or conduit bodies of dimensions less than those required in 314.28(A)(1) and (A)(2) shall be permitted for installations of combinations of conductors that are less than the maximum conduit or tubing fill (of conduits or tubing being used) permitted by Table 1 of Chapter 9, provided the box or conduit body has been listed for, and is permanently marked with, the maximum number and maximum size of conductors permitted.
2014 Code Language:
314.28(A)(3) Smaller Dimensions. Listed boxes or listed conduit bodies of dimensions less than those required in 314.28(A)(1) and (A)(2) shall be permitted for installations of combinations of conductors that are less than the maximum conduit or tubing fill (of conduits or tubing being used) permitted by Table 1 of Chapter 9.
Listed conduit bodies of dimensions less than those required in 314.28(A)(2), and having a radius of the curve to the centerline not less than that indicated in Table 2 of Chapter 9 for one-shot and full-shoe benders, shall be permitted for installations of combinations of conductors permitted by Table 1 of Chapter 9. These conduit bodies shall be marked to show they have been specifically evaluated in accordance with this provision.
Where the permitted combinations of conductors for which the box or conduit body has been listed are less than the maximum conduit or tubing fill permitted by Table 1 of Chapter 9, the box or conduit body shall be permanently marked with the maximum number and maximum size of conductors permitted.
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314.28(A)(3) Pull and Junction Boxes and Conduit Bodies. Smaller dimensions.
Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:What is required for a conduit body with smaller dimensions than are normally required for a typical angle pull for a group of 4 AWG conductors?
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