Metallic Enclosure Supplementary Bonding

[kmh1]

I am grappling with the issue of supplementary bonding to ground for metallic enclosures. Typically I have seen larger metallic control system enclosures bonded to ground using a separate insulated ground conductor (typically #2/0) presumably to minimize the risk of someone touching the cabinet and ground (building steel) and creating a lower impedance path to ground versus the bonding conductor in the power or control cables. When does this cease to become a concern as most smaller metallic junction boxes I have seen typically only rely on the bonding conductor in the cable to ground the box.

 

[jbartos]

Suggestion: Visit

http://www.ormec.com/motion/mktdocs/shldgrnd.htm

For: Use ground straps made from 1 inch (25 mm) silver tinned flat copper braid to connect the cabinet door(s) to the enclosure, the first sub-panel to the enclosure, and from each sub-panel to the next.