Armored Cable "bond strip" as an EGC


  #1  
Old 05-08-09, 02:29 PM
P
Member
Thread Starter
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
Received 0 Votes on 0 Posts
Armored Cable "bond strip" as an EGC

On the issue of the "bond strip" contained in Armored Cable serving as an Equiptment Grounding Conductor, I cite
"Electrical Grounding" , 4th edition, auth R O'Reilly. O'Reilly states---

"The metal strip in Armored Cable is neither designed nor put there with the intent that it be used as an Equiptment Grounding Conductor. The primary purpose of the strip is to maintain continuity----. The outer flexible Armor ALONE is depended on to conduct any fault-current , and to have sufficiently low impedance."

O'Reily considers a possible problem with "new" Armored Cable---

"The trend to thinning the flexible outer armor amplifies concern for using flexible metal as an Equiptment Grounding Conductor"

The Code requires that any metallic surface that may become "energized" be Bonded to an Equipment Grounding Conductor with reliable and "solid" bonding connections. The "bond strip" contained inside Armored Cable is "loose" , and at no point is the "strip" Bonded to tha cable armor,or any other metallis surafce, and the Code not not require such.
 
  #2  
Old 05-08-09, 06:40 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 14,968
Received 598 Votes on 512 Posts
I would imagine your post has to do with this post: http://forum.doityourself.com/electr...cepticles.html

I would agree with much of the info you have posted. The bonding strip in AC cable is not the equipment grounding conductor. It is only there to insure a low impedance path between the cable armor. While it is not bonded to the cable, the bonding strip is in "intimate contact with the armor for its entire length" which is required by article 320.100 (2005)

If you have BX that does not have the bonding strip you really have nothing more than Flex metal conduit which requires a separate grounding conductor (with a few exceptions).
 
  #3  
Old 05-09-09, 01:02 PM
P
Member
Thread Starter
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
Received 0 Votes on 0 Posts
The bonding strip in AC cable is not the equipment grounding conductor. It is only there to insure a low impedance path

If you have BX that does not have the bonding strip you really have nothing more than Flex metal conduit which requires a separate grounding conductor

To repeat from "Electrical Grounding " ----------

"The primary purpose of the strip is to maintain continuity "

"The flexible Armor alone is to have --- sufficiently low impedance"

Flexible Metal Conduit , and Armored Cable , with of with out the strip ,are two completely distinct and different Wiring Methods , and each Method has it's own seperate Article with different installation requirements in accordance with the repective Article..
 
  #4  
Old 05-09-09, 01:58 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 33,575
Received 15 Votes on 13 Posts
Flexible Metal Conduit , and Armored Cable , with of with out the strip ,are two completely distinct and different Wiring Methods , and each Method has it's own separate Article with different installation requirements in accordance with the respective Article..
Perhaps you could expand on that for us non electricians. I've Googled before but only came up with one is aluminum and one steel. I don't think I have ever used MC but I'm guessing it is solid with corrugations sort of like a gas connector instead of interlocked individual rings of AC.
 
  #5  
Old 05-09-09, 03:44 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 14,968
Received 598 Votes on 512 Posts
There are a few types of MC cable.

Standard MC has a interlocking outer sheath smiler to AC cable. It has Mylar wrapped around the conductors and has a green insulated ground wire. The outer sheath alone is not approved as a ground

The newer MCAP also has a outer armor like AC cable but instead of a insulated ground wire is has a #10 aluminum bonding strip in intimate contact with the outer armor. This is most like AC cable (BX) with the exception of it has a Mylar wrap around the conductors. The outer armor is approved as a ground using approved fittings.

The one you mentioned, with the continuous corrugated sheath, is called Core Clad. Its outer sheath is listed as a ground with approved fittings.

@ PATTBAA -
Your book is fine but if you look in the code book you will find that AC cable without the bonding strip is not an approved wiring method. I site again 320.100 (2005) "Construction Specifications" of AC cable. The bonding strip must be there in order to be approved for grounding. Therefore, if it doesn't have the strip, it is not approved to today's codes and may not be used as a ground. If you want to go the MC cable route look at 250.118(10) (2005)
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: