Fill in the blanks with the appropriate answer.
When determining ampacities of conductors for underground circuits rated between 2,001V and 35,000V, where burial depths are modified from the values shown in a figure or table and where burial depths are increased in part(s) of an electrical duct run, no ________ in ampacity of the conductors is needed, provided the total length of parts of the duct run increased in depth is less than __ % of the total run length.
A) increase / 10
B) change / 50
C) decrease / 25
D) increase / 25
Find the Answer
Answer: C
Section 310.60 of the 2014 NEC outlines the general wiring requirements for conductors rated 2,001V to 35,000V. As noted in 310.60(B)(2), “Where the burial depth of direct burial or electrical duct bank circuits is modified from the values shown in a figure or table, ampacities shall be permitted to be modified as indicated in (C)(2)(a) and (C)(2)(b).” Part (a) notes, “Where burial depths are increased in part(s) of an electrical duct run, no decrease in ampacity of the conductors is needed, provided the total length of parts of the duct run increased in depth is less than 25% of the total run length.”
Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at [email protected].