aemeijers wrote:
Nate Nagel wrote:
aemeijers wrote:
David Nebenzahl wrote:
On 8/20/2009 11:05 AM spake thus:
On Thu, 20 Aug 2009 10:56:39 -0700, David Nebenzahl
wrote:
Not according to publishers of the NEC, it isn't.
"The equipment grounding conductor ... shall be one or more ... of
the following: ... Electrical metallic tubing...." [2008 NEC,
Article 250.118]
I imagine they know a little more about it than you do.
EMT in a dry location - OK. But with humidity, and particularly
humidty and vibration, the integrity of the ground suffers in a
short
time. I would never depend on the EMT for a safety ground.
This seems to be analogous to backstabbed connections vs.
screw-terminal connections: allowed by the NEC, but not as good a
technique.
Think about it: with EMT, all it takes is one loose screw
somewhere in the line to sever, or at least seriously degrade, the
ground connection.
That is true if you use a green wire ground too. Workmanship is the
key to any installation. Most of the industrial jobs I inspected
specified compression connectors wrench tight. That is a pretty solid
ground path. They still pulled a green wire most of the time.
Yes. I forgot to mention that when I run conduit, I much prefer the
compression connectors to the
"make-a-dimple-in-the-tubing-with-a-screw" ones, which always seem a
bit on the cheesy side to me.
Chuckle. At work, on certain data circuits, they braze or epoxy the
joints on the conduit, done with compression fittings. Before they
pull the copper or fiber, of course. Of course, a ground path isn't
what they are after.
--
aem sends...
do they also happen to have walls covered with sheets of copper
soldered together? I've worked in some places like that...
nate
Nah, the hardware itself is shielded now. But there are some storage
rooms in the dungeon, now used for other things, that are covered with
expanded metal mesh over the concrete block, and in the plastered
ceiling. There is one room that I suspect has the sort of wallpaper you
describe, but thankfully I'm not allowed in there. The paperwork to be
allowed in the room in front of that room, and use the hardware there,
was bad enough.
--
aem sends...
y'know, now that I think about it, once upon a time expanded metal mesh
was used for lath for plasterwork. I know my high school was
constructed that way; not sure why they spec'd plaster and not drywall
as it was built in 1972 or 1973 I believe. Wouldn't that play holy hell
with radio reception? Obviously people weren't trying to listen to the
radio or watch TV inside a high school, but I'm sure quite a few homes
were built like this as well...
nate
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