Q. The insulation of batteries rated greater than 250V may be all but which of the following?

  1. Air may be the insulating material if a minimum separation of 2 inches is maintained between live battery parts of opposite polarity (battery voltage not exceeding 600V).
  2. Air may be the insulating material if a minimum separation of ½ inch is maintained between live battery parts of opposite polarity (battery voltage not exceeding 600V).
  3. Bakelite or other insulating material.
  4. Mycarta or other insulating material.

Answer: B

As per 480.7, "The provisions of 480.6 shall apply to storage batteries having the cells connected so as to operate at a nominal voltage exceeding 250V, and, in addition, the provisions of this section shall also apply to such batteries. Cells shall be installed in groups having a total nominal voltage of not over 250V. Insulation, which can be air, shall be provided between groups and shall have a minimum separation between live battery parts of opposite polarity of 50 mm (2 in.) for battery voltages not exceeding 600V."

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.