Module grounding revisited [RE-wrenches]

[William Miller]

Friends:

I am researching some new module mounting for rooftops-- more on that later
as it develops.  One question pertinent to the design is module frame
grounding.  One concept I had been wanting to research is that of grounding
only the rack frame.  The Code seems to allow this:

	690.43 Equipment Grounding.
	Exposed non–current-carrying metal parts of module frames, equipment,
	and conductor enclosures shall be grounded in
	accordance with 250.134 or 250.136(A) regardless of voltage.

Researching further:

	250.136 Equipment Considered Effectively Grounded.
	Under the conditions specified in 250.136(A) and (B), the
non–current-carrying
	metal parts of the equipment shall be considered effectively grounded.
	(A) Equipment Secured to Grounded Metal Supports. Electrical equipment 
	secured to and in electrical contact with a metal rack or structure provided 
	for its support and grounded by one of the means indicated in 250.134. 
	The structural metal frame of a building shall not be used as the required 
	equipment grounding conductor for ac equipment.

Therefore, if one grounds a rack frame, the modules being "secured to and
in electrical contact with" the racks renders the module frames
"effectively grounded".

Comments?

William Miller


PS:  I am now using the CD version of the 2002 NEC.  It really makes this
research easier.


WM




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William Miller
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