Ground fault problem, additional thoughts [RE-wrenches]

[William Miller]

Friends:

When I get interested in a subject, I tend to look into it pretty
thoroughly.  Here are a few additional thoughts on the subject:

1. I can't find it now, but a post today suggested that the steel building
structure should have been bonded.  This is SO true.  I am slapping myself
for forgetting this point.

2. Also, while a GF breaker would probably have saved the day (I say
probably because there are still a few questions unanswered-- see my recent
post to the list and Rick Cullen), I believe a simple breaker between the
ground and negative buss would have stopped the ground fault current-- no
need to interrupt the array positive current.  I am not saying I would do
this, there is something instinctively wrong with this idea, as in no one
would know the breaker had opened, etc.

3. Note that GF protection of AC circuits is required when ground fault
current exceeds a range of 4 to 6 mA.

4. Here is the definition of a ground fault current path from the NEC:

Ground-Fault Current Path. An electrically conductive path from the point
of a ground fault on a wiring system through normally non–current-carrying
conductors, equipment, or the earth to the electrical supply source.
FPN: Examples of ground-fault current paths could consist of any
combination of equipment grounding conductors, metallic raceways, metallic
cable sheaths, electrical equipment, and any other electrically conductive
material such as metal water and gas piping, steel framing members, stucco
mesh, metal ducting, reinforcing steel, shields of communications cables,
and the earth itself.


5. From section 250.30 (3):

(d) Bonding. Where exposed structural steel that is interconnected to form
the building frame or interior metal piping exists in the area served by
the separately derived system, it shall be bonded to the grounding
electrode conductor in accordance with 250.104.


Lastly, I want to thank all of you that contribute to these discussions.  I
value highly this forum where so much expertise comes together.  We need to
make certain that not even one more fire is created by RE equipment.

William

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William Miller
Miller Power and Communications
PO Box 50, Santa Margarita, CA 93453
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email: wrmiller at slonet.org
http://millerpowerandcomm.com
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