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Tuesday, June 18, 2019

Question:

Re: CQD answer published Monday, June 10, 2019 -Splices in Cabinets

Hey Charlie, Noticed that the answer to the question regarding splicing in a panelboard cabinet didn't include allowing for the conductors, splices, and taps. So, we have to include all these components when considering the permitted 75% of the space to be utilized not just the conductors. How about commenting on how one determines the space in the panelboard that is under consideration? In addition, it is common for the wiring space at the sides, top and bottom of the cabinet to differ. Thanks for considering responding to these points,

Phil Simmons
A

Answer:

Hey Phil thanks for your comments. You are correct we should have provided a more complete answer. Panelboard manufacturers provide wiring space based on 408.55, including the exceptions, and meeting UL 67 the product standard for panelboards. As you mention the space at the top, sides and bottom can have different dimensions based on Table 312.6(A) and 312.6(B). Conductors are not allowed to fill the cross sectional area of the wiring space in a cabinet to more than 40% as stated in 312.8(A)(1). And the total area of conductors, splices and taps cannot exceed 75% of that cross sectional area. The NEC does not have specific details for determining the space of splicing devices so if the manufacturer does not provide dimensions making a measurement in the field can be necessary.

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CHARLIE TROUT: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

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