Grounding in Control Panels

[rwilsond]

Section 409.60 of the 2005 NEC refers to "Multisection industrial control panels", but there is no definition. What would be an example of a Multisection industrial control panel? Would it be multiple sub-panels in a common enclosure?

Also, the second sentence of 409.60 seems ambiguous. Is a grounding bus required for a Multisection industrial control panel?

 

[lhmida]

I believe that the NEC is talking about separate metal control enclosures connected together by screws, bolts and or wire connectors, or even just abutted up against each other. You have the option of using an approved common grounding bus that some manufacturers offer that runs through all the separate panels or you can use separate approved grounding lugs/bars on each panel.

You don't have to use a bus. But you do have to ground each separate panel. And all grounds must be bonded together. You cannot rely on screws, bolts etc to carry a ground fault.