MC/BX/AC, please clarify. Also, what cut and bush do you use?

[electrofelon]

I don't disagree that half the industry info is flaky at best. As far as sensitive electros, I work around CNC machines. If you have never been around, picture about 5 super computers, several VFDs, about 20 SMPS, tons of serial encoders, and the list goes on. They are certainly industrial, but usually 6-8 figures new, so.....if a piece of wire can potentially protect it, it gets done.

Yeah I used to run a CNC machine, and have hooked several up. I mostly wire up labs now hooking up things like mass spectrometers. I don't hesitate to use conduit as the EGC even in these things. They would actually work totally fine with no EGC at all. What exactly do people think the ground does that makes something electronic work better?

 

[darekelec]

How does International Space Station work without being connected to ground?

 

[fastline]

Yeah I used to run a CNC machine, and have hooked several up. I mostly wire up labs now hooking up things like mass spectrometers. I don't hesitate to use conduit as the EGC even in these things. They would actually work totally fine with no EGC at all. What exactly do people think the ground does that makes something electronic work better?

It's more about redundancy, to ensure the machine chassis and bits stay at ground potential. Static electricity can kill a FET or diode dead as a doornail....fact.
The other is personal safety, at least on CNC machines. You have 100gal of conductive coolant splashing all over while pumping 100HP of juice through it. There are ways for bad things to happen and if a big 3P motor jumps over to ground, I want to make sure there is a perfect path to blow that breaker.

Not saying it is the only or right way, just something I prefer.

 

[jim dungar]

It's more about redundancy, to ensure the machine chassis and bits stay at ground potential.

Actually it is more about keeping the machine parts and operator to the same reference potential, dirt has nothing to do with it.

 

[darekelec]

After installing heavy cable in vertical runs is there a higher chance that conductors of Mc cable will slide out from jacket because of gravity ?

 

[infinity]

After installing heavy cable in vertical runs is there a higher chance that conductors of Mc cable will slide out from jacket because of gravity ?

Absolutely I've seen it happen. We had guys installing a 500 kcmil MC temp riser about 10 stories and when the lifted the end to make it all straight it slid right out.

 

[electrofelon]

Absolutely I've seen it happen. We had guys installing a 500 kcmil MC temp riser about 10 stories and when the lifted the end to make it all straight it slid right out.

Quit for the day, go to bar

 

[infinity]

Quit for the day, go to bar

I know. Funny thing is I told one of these guys to secure the conductors so that they don't move when they straighten it out shortly before they straightened it out and they slid down 10 floors.

 

[darekelec]

southwire makes mc cable for vertical applications

Armorlite Riser MC™ Cable​

Is there something in the code that cable has to be shaped in letter C every so feet ? similarly to vertical conductor supports in conduit to prevent conductors from sliding out.

 

[zooby]

If "you" are having that many issues from stripping mc.....there's an issue. And not with the mc.

 

[winnie]

I Actually hate MC and dont understand why it is so popular. I would love to not have to terminate all these stupid wire EGC's - what a waste of materials and labor. MC-AP does that, just not sure why that stuff is not as universal as MC, seems like a no brainer to me. But the green wire cult is very very strong.

You do know that you are _permitted_ to terminate the wire in MC-AP as a wire EGC

 

[winnie]

Uggh! How about the manufacturer recommended Roto-Split? Sure, maybe a bit more work but you get a clean armor cut because it cuts with a saw blade at the proper angle.

-Hal

I wish I had something like a Roto-Split, but with the blade angled so that the cut end of the armor was at a more blunt angle.

 

[electrofelon]

It's more about redundancy, to ensure the machine chassis and bits stay at ground potential. Static electricity can kill a FET or diode dead as a doornail....fact.
The other is personal safety, at least on CNC machines. You have 100gal of conductive coolant splashing all over while pumping 100HP of juice through it. There are ways for bad things to happen and if a big 3P motor jumps over to ground, I want to make sure there is a perfect path to blow that breaker.

Not saying it is the only or right way, just something I prefer.

Just wanted to add that there are certainly times when shielding and bonding are important. VFD's are a common case that can make lots of "noise". BUT......that is shielding and bonding and doesn't have much of anything to do with the EGC going back to the serving source.

 

[infinity]

You do know that you are _permitted_ to terminate the wire in MC-AP as a wire EGC

You can but that kind of defeats the purpose of using MC-ap which is to not have to terminate a wire type EGC. Whenever I see an installation where someone landed the #10 aluminum conductor (instead of just cutting it off flush with the end of the cable) I assume that they didn't know what they were doing.

 

[garbo]

I have never had those problems. The chosen bushings should be large enough that the ends overlap when pushed into the sheath, and turned so the split is 180 deg. from the cut ends of the metal.

And I have no trouble re-shaping the cut ends of the sheath so there is no sharp edge against the wires even without a bushing. I use bushings with AC/BX and FMC, but not with MC, with its plastic liner.

I have been cutting the edge of AC & MC cable at a 45 degree angle for last 45 years. I always had several bags of different size anti short bushings. Hated when they supplied undersized anti shorts. If I was using 1/2 & 3/4" greenfield that entered a condulet or other threaded fitting would install large bushing. Side note: After I used extra oily aluminum 12/2 MC asked for steel jacket when pulling from a reel up into drop ceiling. While rushing to reinstall drop ceiling titles got oil prints on them. Usually carried some rags on my work cart. Like another person posted AC ( BX ) is rarely seen outside of houses. Must use far superior MC cable in commercial buildings.

 

[Eddie702]

I agree I just saw cur it and remove as much burr as possible with a jackknife and a red head even if it's not requires. Never had an issue but these were always smaller cabler #14, #12 and #10.

 

[electrofelon]

: After I used extra oily aluminum 12/2 MC asked for steel jacket when pulling from a reel up into drop ceiling. While rushing to reinstall drop ceiling titles got oil prints on them. Usually carried some rags on my work cart.

Yeah hate that extra oily MC. . Can we skip the "dip MC in oil" manufacturing step please