Module grounding revisited [RE-wrenches]

matthew tritt solarone at charter.net
Tue Oct 29 17:32:17 PST 2002


William,

Good work! Wiring all those module frames, in spite of the frames being
themselves grounded, has seemed
totally re-diculoso to me for a long time. I hope "they" buy your argument.

Matt
----- Original Message -----
From: "William Miller" <wrmiller at slonet.org>
To: <RE-wrenches at topica.com>
Sent: Tuesday, October 29, 2002 2:04 PM
Subject: Module grounding revisited [RE-wrenches]


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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