Code Quiz

May 21, 2004 12:00 PM, By Steven Owen

Q. Two 480V motor control centers (MCCs) are located directly across the aisle from one another and face each other in an electrical distribution room. They’re exactly 48 inches apart, which complies with Table 110.26(A)(1) for a Condition 3 spacing requirement. One of the existing MCCs is set to be replaced with a new MCC that’s 5 inches deeper, but the existing MCC is set against a wall, so the new MCC will have to be installed in the exact location. This will cause the new MCC to extend 5 inches into the required working space between the two MCCs. The proposed installation will allow 43 inches between the MCCs (front-to-front). What is the minimum spacing required for this proposed installation to be Code compliant?

A) 48 inches
B) 43 inches
C) 42 inches
D) 36 inches

Answer: C

Explanation: In 110.26(A)(1)(c), the 2002 NEC permits a reduction of 6 inches by re-classifying a Condition 3 space to a Condition 2 space. This is reducing a 48-inch minimum space to a 42-inch minimum space. This is allowable when conditions of maintenance and supervision ensure that written procedures have been adopted to prohibit equipment on both sides of the aisle from being open at the same time, and qualified persons who are authorized will service the installation.

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states.