[RE-wrenches] Grounding - Exposed Metal Part

[Hans Frederickson]

Mark,
If you look at NEC 250.104(C), you'll find that you have to bond structural
metal that is "likely to become energized". The phrase "likely to become
energized" is not defined, and is up to the AHJ. I would guess most AHJ's
would consider the second metal plate to already be bonded since it is
electrically continuous with the first metal plate, because they're
touching. I also doubt they would consider it "likely to become energized"
because you bonded the first metal plate. Just my opinion.

-Hans 

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mark Frye
Sent: Wednesday, July 25, 2012 7:29 PM
To: RE-wrenches
Subject: [RE-wrenches] Grounding - Exposed Metal Part

A bare metal plate is connected to a conduit which serves as an equipment
ground. The plate is grounded and needs to be grounded because it could
become energized both by being contact with the conduit which could become
energized and also by coming into contact with the current carrying
conductors themselves.

A second bare metal plate touches the first plate but could not come into
contact with the current carrying conductors.

True or false, the second plate does not have to be grounded (bonded to the
first plate) because the first plate is already grounded and therefore could
not cause the second plate to become energized?

Any Code references to support your opinion?

P.S. I believe: "false", the second plate must be bonded to the first plate
because it may become energized by the first plate regardless of whether or
not the first plate is actually grounded, but I can't find references in the
Code to support this.

Mark Frye
Berkeley Solar Electric Systems
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