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Industrial Wiring Question


ktaulbee
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Does anyone know the rules for when running a two wire single phase circuit in an industrial setting is allowed? I'm having trouble getting a straight answer back on this and have been looking in the NEC 250.118 because this is what the company stated exempted them from needing an equipment grounding conductor present. I had been told in the past that only three wire single phase circuits were permitted in industrial settings like this one, however, if this is true then I'm having trouble finding it in the standards.

Other information: Circuit run in EMT conduit, 50 - 60 ft from breaker box, four feet in height off floor adjacent to conveyor lines, with three metal four-plex receptacles, high (forklift) traffic area, 7 employees regularly in area.

Any help?

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Originally posted by ktaulbee

Does anyone know the rules for when running a two wire single phase circuit in an industrial setting is allowed? I'm having trouble getting a straight answer back on this and have been looking in the NEC 250.118 because this is what the company stated exempted them from needing an equipment grounding conductor present. I had been told in the past that only three wire single phase circuits were permitted in industrial settings like this one, however, if this is true then I'm having trouble finding it in the standards.

Other information: Circuit run in EMT conduit, 50 - 60 ft from breaker box, four feet in height off floor adjacent to conveyor lines, with three metal four-plex receptacles, high (forklift) traffic area, 7 employees regularly in area.

Any help?

As Tom pointed out, 250.118(4) allows the EMT to be the equipment grounding conductor. If that's how they've configured it, then then the EMT is the third conductor.

- Jim Katen, Oregon

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Originally posted by StevenT

I agree with the EMT/3rd conductor, but I think it's use should be limited. I lost count of how many times I've seen EMT disconnected from it's connector/coupling. POOF! No more ground!

Even worse than that. Last year, I was involved in a project that involved rebuilding a residential care facility that had suffered severe damage from a fire. The fire was caused by arcing across a loose EMT connection that was carrying a fault.

However, to the best of my knowledge, the NEC still allows EMT to be used as an equipment grounding conductor. There doesn't seem to be any restriction on it in industrial settings.

- Jim Katen, Oregon

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While there can certainly be a break in conduit, how is it any different than any other poorly made electrical connection? IOW, I've seen plenty of crappy connections with ground wires, split shot that wasn't crimped, or other lousy workmanship with NMC.

I see nothing but EMT. No NMC in Chicago. If you can see the conduit, you can "see" the ground path. Check the couplings and connection points; if both screws are seated, you know it's OK.

I think all the misconceptions about conduit come from lack of experience with the material. For every "problem" folks imagine with EMT, I can think of any number of problems with NMC.

And, most important to me anyway, is we get to use 4x4 STEEL BOXES w/ LOTS OF ROOM IN THEM. And, there's nothing like a nice mud ring for finishing the drywall to. And color coding when you have a bunch of 3 way switches and complex circuits all running through the same area. And getting wires safely through nasty bad messes of framing in old houses where you can't get clearance to prevent drywall nails from getting pounded through NMC. And the beauty of a nice series of bends and offsets at a raceway. And, and, and....... Shoot, if one can't figure out how to connect conduit, run a strand of green in the pipe and really be safe.

I can't imagine having to slum around with plastic boxes and NMC. Makes me shudder.......

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Originally posted by kurt

While there can certainly be a break in conduit, how is it any different than any other poorly made electrical connection?

It's on the outside. With other methods, the connections are inside boxes.

IOW, I've seen plenty of crappy connections with ground wires, split shot that wasn't crimped, or other lousy workmanship with NMC.

I see nothing but EMT. No NMC in Chicago. If you can see the conduit, you can "see" the ground path. Check the couplings and connection points; if both screws are seated, you know it's OK.

Yes. But many, if not most, of those connections are in places that you can't see.

I think all the misconceptions about conduit come from lack of experience with the material. For every "problem" folks imagine with EMT, I can think of any number of problems with NMC.

There are problems associated with both systems. That doesn't mean that problems with EMT are imagined.

And, most important to me anyway, is we get to use 4x4 STEEL BOXES w/ LOTS OF ROOM IN THEM. And, there's nothing like a nice mud ring for finishing the drywall to.

I can't imagine having to slum around with plastic boxes and NMC. Makes me shudder.......

Ah, but we both know that the reason Chicago uses EMT has nothing to do with safety and everything to do with unions. I'd like to see some hard data showing that EMT installations have fewer fires than EMT installations.

- Jim Katen, Oregon

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Originally posted by Jim Katen

[

Yes. But many, if not most, of those connections are in places that you can't see.

Ummm, unless one happens to look before the wall finish goes on.

There are problems associated with both systems. That doesn't mean that problems with EMT are imagined.

Where'd I say that?

Ah, but we both know that the reason Chicago uses EMT has nothing to do with safety and everything to do with unions. I'd like to see some hard data showing that EMT installations have fewer fires than EMT installations.

- Jim Katen, Oregon

(I know you didn't mean to say EMT twice....)

What's that got to do with it? I doubt such data exists. Fires is fires, and they can usually be traced to something stupid that someone did or didn't do.

And, it's not everything and nothing. We have solid masonry buildings. It's most of the city. Let's run NMC through the masonry, that'd work, right? Or, let's reconfigure this 100 year old mess with NMC, and how exactly do we get all the necessary clearances in the framing?????

Work with it on a regular basis over several years, and I would almost guarantee you'd change every tune you ever imagined about EMT installs. It's folks that don't have enough experience with the material that find it confusing and suspect.

Personally, I'd have it all be EMT w/some green in it in my perfect world. [:-angel] Even Douglas hizzelf sez that'd be the berries.

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Originally posted by kurt

Originally posted by Jim Katen

[

Yes. But many, if not most, of those connections are in places that you can't see.

Ummm, unless one happens to look before the wall finish goes on.

There are problems associated with both systems. That doesn't mean that problems with EMT are imagined.

Where'd I say that?

Ah, but we both know that the reason Chicago uses EMT has nothing to do with safety and everything to do with unions. I'd like to see some hard data showing that EMT installations have fewer fires than EMT installations.

- Jim Katen, Oregon

(I know you didn't mean to say EMT twice....)

What's that got to do with it? I doubt such data exists. Fires is fires, and they can usually be traced to something stupid that someone did or didn't do.

And, it's not everything and nothing. We have solid masonry buildings. It's most of the city. Let's run NMC through the masonry, that'd work, right? Or, let's reconfigure this 100 year old mess with NMC, and how exactly do we get all the necessary clearances in the framing?????

Work with it on a regular basis over several years, and I would almost guarantee you'd change every tune you ever imagined about EMT installs. It's folks that don't have enough experience with the material that find it confusing and suspect.

Personally, I'd have it all be EMT w/some green in it in my perfect world. [:-angel] Even Douglas hizzelf sez that'd be the berries.

You're trying to turn this into an argument about EMT vs. NM. I don't have a problem with EMT installations per se. It's a fine system. However, I think that it's a poor practice to use the tubing as the grounding conductor, even though it's allowed by the NEC.

That's my sole gripe with it.

Which do you think is a better installation, EMT with a seperate grounding conductor or EMT with the tubing as the grounding conductor?

- Jim Katen, Oregon

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I'm not trying to turn this into an argument of one vs. the other. I'm trying to educate the outlanders.

A preponderance of opinion is/was talking like EMT was dangerous ("a defect caused a fire!"). It's a wonderful way to wire a building. And before I'm through, and I'm never through, telling folks they're trying to do one thing or another is Rovian, as it deflects thoughts away from issues to focus on personalities.

I've presented the other side. A preponderance view of those that don't use it regularly is EMT has problems. Sure does. Not unlike everything else. The benefits wildly outweigh the problems though, not the least of which is one can run a separate grounding conductor in the tubing.

One is allowed to imagine it's poor practice to use tubing as the grounding conductor, even though it's allowed by the NEC. Before I think it's poor practice, I'll have to figure out how a nice big chunk of conductive material bonding all the components of a system together is poor practice.

Tubing with an additional grounding conductor is as good as it gets, IMHO. Stack on all the other benefits, and one falls in love with it very quickly.

Final note is it's beautiful to behold. Seeing open structure with nice shiny steel, solidly mounted equipment, and well formed bends is a great way to live.

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Kurt,

I'm not trying to say that EMT is bad, or NM is better. In NYC, EMT and BX have been the standard for quite a while. Yes, these days NM is accepted in certain residential. With both materials, a bad installation is bad.

I also like a separate ground besides the conduit. I'm not thinking about inspecting it, which in a perfect world would bring to light anything disconnected. I'm thinking about installations that are not inspected, where simply during normal everyday use, with folks walking all over the stuff like it was a ladder, connections come loose and the ground is gone.

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Sure. It's never been an argument about which one is better, at least not from my end.

Heck, we've tried to pry apart connections, and it's darn near impossible, so that whole "it comes apart" argument doesn't go far with me. Install it like crap, and it's crap. Get it right, and you darn near can use it as a ladder. The only good argument against it is cost basis.

Yep, it's expensive.

As much as anything, I like the sturdiness, and the 4x4 deep metal boxes that I can finish with a mud ring.

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