The plant manager wants you to solve a large collection of related complaints. Over the past year, employees in the administrative offices have complained about getting shocked or at least feeling an uncomfortable tingle when turning lights on or off in the office space or the bathrooms. They get the same “surprise” from water fountains. Several have commented that it’s time to stop blaming it on static electricity from the carpet.
In the plant, employees have made similar complaints. In addition, an electrical apprentice reporting receiving a mild shock when he touched a switchboard panel to open it. His DMM subsequently did not read a voltage there. What’s going on?
It’s interesting that all of the complaints have to do with general equipment that’s covered by Chapter 4. Article 404 covers switches and Art. 408 covers switchboards and panelboards.
Since a current (shock) is being passed, we know those switch faceplates are metallic. The way to fix this is to bond the metal faceplate to the equipment bonding conductor. You will find the requirements for correctly doing this in Art. 404.9. Note that the switch yoke must always bond to the equipment grounding conductor; you may need extensive work to bring the installation up to code.
A shock from a panelboard indicates violations of Art. 408. The most common one that leads to this problem is the metal cabinet is not bonded to the equipment grounding conductor. You may have to install a terminal bar to fix this.
