Colored Electrical Outlets

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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.
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On Tue, 18 Aug 2009 15:15:22 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

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.
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On 8/19/2009 8:47 PM snipped-for-privacy@snyder.on.ca spake thus:

>>

>

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.
--
Found--the gene that causes belief in genetic determinism

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On Thu, 20 Aug 2009 10:56:39 -0700, David Nebenzahl

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.
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On 8/20/2009 11:05 AM snipped-for-privacy@aol.com spake thus:

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.
--
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On Thu, 20 Aug 2009 11:19:14 -0700, David Nebenzahl

The problem is, the NEC allows either one to be used as a ground - and the "dimple" is NOT a safe ground. The compression connector, wrench tite - perhaps.
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snipped-for-privacy@snyder.on.ca wrote:

I'm sure the code making panel will be interested - submit a code change proposal. Be sure to include pictures of the dead bodies - it is very effective. On the other hand, the code panels are not likely to make changes based only on opinion.
"Dimple" is not a good description, as there were also fittings that used a compression tool to create a "dimple". (They still allowed?)
In addition to using compression fittings you can use non-diecast fittings (not sure what they are called). They are a lot better connection on set-screw fittings. Or compression non-diecast fittings.
--
bud--

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David Nebenzahl wrote:

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...
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aemeijers wrote:

do they also happen to have walls covered with sheets of copper soldered together? I've worked in some places like that...
nate
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Nate Nagel wrote:

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...
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aemeijers wrote:

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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Nate Nagel wrote:

No, the wall mesh in these rooms was obvious RF sheilding. You could see where there used to be a mesh door to complete the cage. I guess they figured floor didn't need shielding, since that part of building was well below grade, with no sewers and such below it.
-- aem sends...
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aemeijers | 2009-08-20 | 10:39:27 PM wrote:

I once watched the construction of a Tempest-class area: * Commercial metal studs * One layer of metal-coated 5/8" wallboard on each side, metal out * Tape seams with metal tape * Another layer of metal-coated wallboard, seams shifted four feet * Tape seams with metal tape * One layer of regular wallboard for the finish surface * Speakers to play music inside the walls * Motion detectors to detect motion inside the walls
They did the ceiling after the walls closed in, so I didn't get to see what happened there, but I'm sure it was equally impressive.
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So long as there is any kind of "connection" a fault will start an arc that will "trip" the CB.
I was installing some foil insulation on a wall with a outlet box. The foil just brushed against the hot wire and FLASH, POP the breaker tripped. I guess the foil had been grounded by another outlet's plaster ears.
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On Tue, 18 Aug 2009 05:31:40 -0700 (PDT), stan

IBM decided IG was snake oil on the late 70s and removed the recommendation from the Physical Planning Manual. You are right, as soon as you connect equipment on different circuits together IG is meaningless, or worse a source of additional problems. Your bonding path becomes longer than the signal path so the line driver/receiver becomes your surge protection. We went the other way and added additional bonding, connecting machine frames directly together.
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On Aug 18, 1:12pm, snipped-for-privacy@aol.com wrote:

I used to work on a mainframe computer system that was updated to isolated grounding. There were a few pieces of hardware on which it was impossible to isolate the grounds but the engineers decided this was OK. I have never seen so much blue smoke in my life as when they applied power. This happened nearly 20 years ago and the essence of ohms still lingers in the air. A few years ago all the equipment wa upgraded and it was all designed for IG and the appropriate IG system was installed. A few months ago the equipment was expanded and it was decide that IG was not needed so now we have bare ground wires laying in bare metal cable trays attached to IG ground points, cable trays are fastened to earth ground.
Jimmie
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JIMMIE wrote:

IMHO IG circuits were largely black magic.
There were a few manufacturers that wanted the isolated ground to be tied *only* to a local ground rod (no connection to the electrical system). It was a major code violation and safety hazard.
--
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snipped-for-privacy@aol.com wrote:

I was an electrician working on the mission control center for the star wars program 20 years ago and we put ground rods under the raised flooring, around the perimeter of the building, then built a grounding grid under the flooring of the whole place. I guess they didn't want any stray electric currents affecting the multi million dollar Cray Super Computer.
TDD
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wrote:

The "u" ground is not connected to the "frame" ground.
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How's the hired gun business working out?
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