Q. When grounding a large bridge crane in an industrial facility, such as a paper mill or steel mill (or any other location), which of the following statements is correct?
A) The trolley frame and bridge frame are considered to be electrically grounded through the bridge and trolley wheels and its respective track.
B) The trolley frame and bridge frame are not considered to be electrically grounded through the bridge and trolley wheels and its respective track.
C) All moving parts, including the trolley and bridge frame that have a metal-to-metal bearing surface are considered to be effectively grounded.
D) An equipment grounding conductor shall be installed along the entire length of the crane rails, bridge, and trolley. This conductor may be placed anywhere on the metal frame of the crane assembly.
Answer: B
Explanation: Per a change to the 2005 NEC (610.61), the trolley frame and bridge frame shall not be considered as electrically grounded through the bridge and trolley wheels and its respective tracks. This section of the Code now requires you to install a separate bonding conductor for grounding the bridge and trolley wheels and its respective tracks.
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.
