A question has arisen related to whether a storage battery installation has the required working space in accordance with the 2008 National Electrical Code. The depth of the battery rack supporting the batteries is 12 inches. It's installed tight against a concrete wall. Directly across from the battery rack is electrical switchgear rated at 600V, with a nominal operating voltage of 480V.

Based on these facts, what is the required minimum depth of the working space in the direction of live parts?

  1. 36 in. from the back edge of the battery rack to the front edge of the electrical switchgear.
  2. 42 in. from the front edge of the battery rack to the front edge of the electrical switchgear.
  3. 48 in. from the front edge of the battery rack to the terminals inside of the electrical switchgear.
  4. 48 in. from the front edge of the battery rack to the front edge of the electrical switchgear.

Answer: D

Article 480 focuses on storage batteries. As noted in 480.9(C), "Working space about the battery systems shall comply with 110.26. Working clearance shall be measured from the edge of the battery rack."

We can determine the required clearances from Table 110.26(A)(1). This particular installation falls under Condition 3, which covers "exposed live parts on both sides of the working space." Looking at the second row (151V to 600V) under the third column (Condition 3) we see that the installation calls for a minimum clearance of 4 ft.

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 necexpert@aol.com.