Question on 220V A/c outlet

[clare]

and the PROPER way to install it was with the bond ribbon bent back over the sheath and captured by the box connector, not cut off flush with the sheath.. Inspectors were not happy if they found an end without the ribbon bent back before the anti-short was installed. The bare ground wire solved that, even though the bond strip was still there and best practice was still to bend it back under the cable connector. The "bond strip" in parallel with the coiled sheath had the effect of electrically shortening the length of the "ground" conductor and eliminating the "choke" effect of the coiled grounding conductor when ground fault current existed. This made it possible to use the sheath as a ground. Previously it was not used AS a ground, but was required to BE grounded.

Since MC cable does not have a bonding ribbon as part of it's spec, a ground wire is pretty well a requirement for most applications - virtually all MC cable I've seen over the last 20 years or so has had an insulated ground wire, while the vast majority of the AC cable I've run into (installed since the sixties) has had a bare ground.

Possibly becuase I don't get involved with wiring in the USA, and GENERALLY Canada has higher electrical safety requirements (or at least different ) than the USA.

As for the "BX" designation, WAY back in the 1800s Greenfield had their model "B" flexible conduit, and in about 1900 they brought out an experimental "B" model flex, which had the wires already installed. When it hit the market, according to the generally accepted version of the truth, it was referred to as "B Experimental", shortened on the order sheets to "BX". Might be "BS", but that's the generally accepted story.

[Robert Green]

Grew up watching my Dad use it (was required in NYC at the time '50-'70) but may not be now. Never heard it called anything but BX cable. (-: I guess it's one of those things like Kleenex or Xerox. The tradename overtakes the common name. I can still remember moving south and seeing Romex for the first time. Oops. I mean non-metallic sheathed cable from the Rome wire company.

-- Bobby G.

[Mikepier]

Then why do they put a seperate green ground conductor in the aluminum MC cable where conventional BX did not have a seperate ground? These days if you go to Lowes or HD, all they have is MC Lite 12/2 with a ground. I think HD still has the "classic" 12/2 steel BX on the shelf with no seperate ground.

[Metspitzer]

I was always told that the bond wire was not for fault current. It was to short the coils of steel so there were no induced current, but I was not able to find a cite faster than I lost interest.

[RBM]

** You are exactly right. It lays across the coils of the cable to assure a straight path for any fault current

[RBM]

Then why do they put a seperate green ground conductor in the aluminum MC cable where conventional BX did not have a seperate ground? These days if you go to Lowes or HD, all they have is MC Lite 12/2 with a ground. I think HD still has the "classic" 12/2 steel BX on the shelf with no seperate ground.

They are simply two different types of cables, which are used for different purposes. For example: In places of public assembly, you can use MC cable , but AC cable is not allowed. Aluminum sheathed AC cable has been on the market since 1959, the same year that the Nec required AC cable to have the bond conductor

[The Daring Dufas]

BX was outlawed around these parts many years ago. There is MC everywhere in buildings in this area, I use a lot of it.

TDD

[The Daring Dufas]

The Romex my dad taught me about had plastic insulated conductors covered with some kind of jacket that was silver and looked sort of like fish scales. It was some sort of fiber reinforced paper, possibly tar paper with a silver finish. We wired the family home with it back in the 1950's and 1960's. Darn, I'm getting old. :-)

TDD

[clare]

My dad was an electrician, and when he came home after working all day with Romex, particularly on a hot summer day, he was BLACK. Was he ever happy when they came out with the plastic sheathed stuff!!! That old stuff was NASTY.

[The Daring Dufas]

I like MC cable since I got a turntable dispenser for rolls of wire coiled like MC is. It comes off straight with no kinks or loops and does make it so much easier to install the cable for long runs.

TDD

[Robert Green]

I have one run of it in the basement where the previous owner's son built a room - probably in the '60s and I always wondered WTF is this stuff? Never seen it before nor since. It really is odd looking stuff compared to what came before and what came after.

In this case, it was two conductor without ground and a neutral drawn from a different circuit because he was tapping off an existing lighting circuit to create a wall outlet. He also paneled the room using furring strips, no insulation or prep and banging holes into weak cinderblock with nails that did a lot of damage. I guess you have to learn somewhere. When I built a darkroom in my parent's basement my plumbing and electrical work didn't look very professional, either.

The rest is old 1940 cloth wiring and my newer blue NM 12 w/G. Bought two

250' reels in 1985 from Hechinger's for $28 - still half plenty of it left. I wonder what it costs now? Rewiring an old, small Cape Cod doesn't take a lot of wire, just a lot of patience. Now at least every circuit that draws more that 10A is on the newer wire. The cloth is still holding up, but it doesn't tolerate a lot of fussing with. But it runs to the attic and then drops down to the various rooms. It was easier to leave that in place and to simply add new runs from the basement to the kitchen and other places where I didn't want to take a chance pulling 15A for space heaters, central vacuum., radial arm saw, etc. on the old cloth wire.

-- Bobby G.

[Twayne]

No , you don't read ANY UL (or any safety spec) and go to work based ONLY on that spec. You have to also read any references it gives, and any specs on how it's connected, to what, and so on. The fact that UL accepts any component is ALWAYS dependent on how that component is used. UL DOES NOT test for real-world applications; it specs what can be connected to it via more specs, NOT components. It is far from putting a UL tag on a complete system when it's only part of a complete system, other parts of which are unknown, so those specs must be interpreted also. Worked meeting UL specs in designs for ten years, compliance to specs for another then.

[bud--]

Another useless post.

I have an old UL standard for Snap Switches (like a wall switch).

For AC only switches the tests include the following - at rated voltage:

10,000 operations at rated current 10,000 operations at rated current and power factor around 0.8 10,000 operations at rated current controlling incandescent loads 100 operations at 4.8x rated current and power factor around 0.5

At the end of all these operations the switch has to still be functional.

How is that not "real-world"?