BX/Conduit Grounding

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  #1  
Old 04-03-01, 06:53 PM
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Why is it that BX is no longer code unless there is a third ground wire included? Isn't the metal shell a ground? Every time I have used BX i always get 120V hot to ground. I though it was just like conduit except flexiable, and more wires could not be pulled through. Do I also have to pull a a ground wire through now when using conduit? Why have there been all these changes in grounding codes in the past few years?
 
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  #2  
Old 04-03-01, 07:18 PM
Wgoodrich
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Why is it that BX is no longer code unless there is a third ground wire included?

An approved equipment grounding path is required for new installations, BX cable did not have a grounding conductor in it and the flex by itself is not considered as an approved grounding path.

Isn't the metal shell a ground?

No, If you will look at what is on the market. Metal clad and type AC cable has replaced BX cable. The metal clad does not have a grounding strip but does have an equipment grounding conductor in the flex. Type AC cable does not have an equipment grounding conductor in the flex, but does have a grounding strip that is required to augment the flex of that cable to consider the flex as an approved grounding conductor. Be aware though that you do not connect the grounding strip at the ends, the strip just runs along the inside of the flex to assist in creating the approved grounding path by making contact the full length of that flex.

Every time I have used BX i always get 120V hot to ground.

Congrats, try touching a wet cement block or a green kiln dried wood stud, you will get the same reading.

I though it was just like conduit except flexiable, and more wires could not be pulled through.

Flexible metallic conduit is approved as a grounding path if listed, marked, and approved for use as a grounding path, but this flexible metallic conduit is much more substantially constructed that the flex containing BX cable.

Do I also have to pull a a ground wire through now when using conduit?

No most metal conduits are accepted as an approved grounding path as long as you use the proper grounding style connections to the metal boxes. However there is a heavy introduction to a resistance calculation and track record of metal conduit coming apart etc. You may find conduit in the near future to be limited in use as a grounding path. There is a strong movement towards that means.

Why have there been all these changes in grounding codes in the past few years?

A national record system recording death, injury, etc. caused by electrical shock of humans and animals has been tracked, the National fire and safety seems to react if enough of these incidents are proven to be caused by a specific wiring method. As we live we learn better ways of making things safe, or at least some say that thought.


Good Luck

Wg
 
  #3  
Old 04-04-01, 04:01 PM
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The reson I ask this is beacuse my Lake House is quite old and was rewired about 15 years ago. Over 90% of the wiring is BX if not all of it. Is this not safe? Am I allowed to expand off of this? I checked all circuits and get 120 hot to ground. What is an option besides BX that would be legal?. Romex is not code and conduit is much too hard to use in many locations. Also, I have baseboard 220v heat off of 20 amp breakers. Could I pull off of one leg of this to install an outlet for my windows AC unit (110).

 
  #4  
Old 04-04-01, 04:51 PM
Wgoodrich
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15 years ago is about the time that metal clad with a grounding wire replaced bx without a grounding wire. Look in what you are calling BX cable and see if a grounding wire in that cable.

If not the NEC allows you to run a single grounding wire but you might want to check with local Code.

Where are you located that forbids nonmetallic sheathed cable to be used ?

Curious

Wg
 
  #5  
Old 04-04-01, 04:57 PM
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just a note,
the BX's outer shell is about 5 times in length of the interior conductors, as ohms law applies to grounds, it makes it a poor one.
also;
you should probably run a home run to your AC unit
 
  #6  
Old 04-04-01, 07:01 PM
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I have checked and I know for a fact that it is BX cable no ground, I looked into it and it is from 1981. Older than I thought. I'm in the Chicagoland area. Do almost all areas allow romex as code. They are starting to tighten down on BX and saying only a 6 foot run i think here. Is it necessary to run a aground wire for safety, etc. Almost impossiable in some areas. Attic 2 feet high at peak at best. That is the problem with the window AC unit i doubt i can get cable up there and it trips breaker alot. I know it isnt exactly code to draw off of a 220V circuit but could i do it with out any danger of getting electricuted, etc. The one thing I don't get is that say sell Romex and Romex Plastic Boxes, wire clips etc. at every hardware store, why is this if it is not code.
 
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