(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 3 of 3

Thread: Grounded Armored Cable?

  1. #1
    DIY Junior Member onestepahead's Avatar
    Join Date
    Jun 2010
    Location
    NJ
    Posts
    2

    Default Grounded Armored Cable?

    Hello-
    My house is over 70 years old. Wired with armored (BX) cable - cloth wrapped hot & neutral inside. No ground wire.

    I've been gradually replacing ancient receptacles with 3-prong ones. I've been pigtailing the ground screw to the metal outlet boxes. I've been testing each box with with a voltage tester (one of those little ones that's just a small light), and I've since acquired one with a digital readout for the last few. Indeed, I'm seeing the same voltage (~124v) from hot to neutral as hot to ground - indicating (i think) that the boxes, via the armored cable, are grounded.
    However, I've recently read some postings claiming that armored cable doesn't provide true ground - that there is so much conductive material joined by the boxes and all of the cable sheathing that current will flow into it, but that there still may be a more direct path to ground in the event of a short circuit.

    so, is that true?

    I have no way to measure the current, only the voltage. Do I have a grounded system?

  2. #2
    Licensed Electrical Contractor Speedy Petey's Avatar
    Join Date
    Jun 2007
    Location
    NY State, USA
    Posts
    975

    Default

    This is very true.

    The problem is not that of finding a different path, it's one that a fault will follow the spiral of the sheathing and not run along it in a linear path. This creates very high resistance and can cause the sheathing to be a heating element instead of a fault current conductor.

    Modern AC cable (~1960's on) has a thin bonding strip that "joins" all the spiral coils and lats fault current flow directly down the cable.
    Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.

  3. #3
    DIY Junior Member partimer 31's Avatar
    Join Date
    Jun 2010
    Location
    Manchester, Vermont
    Posts
    12

    Default

    Speedy Petey answer was very good. I would just add, If the amored cable is not a good grounding conductor, install GFCI duplex receptacles. This is an opinion on mine. Replacing the old BX cable is better, if you have the funds to do this.??

Similar Threads

  1. Cable V
    By Barry J in forum Computers and Stuff
    Replies: 3
    Last Post: 02-19-2010, 07:20 PM
  2. Cable or Jet?
    By Nate R in forum Drain Cleaning
    Replies: 14
    Last Post: 01-09-2010, 07:01 AM
  3. No 6 AWG Cable
    By devans175 in forum Electrical Forum discussion & Blog
    Replies: 7
    Last Post: 09-12-2009, 06:33 PM
  4. Cable Drain (long cable needed)
    By dick2222 in forum Plumbing Forum, Professional & DIY Advice, Tips & Tricks
    Replies: 2
    Last Post: 06-11-2009, 07:03 PM
  5. improperly grounded panel?
    By Bob in Maine in forum Electrical Forum discussion & Blog
    Replies: 7
    Last Post: 07-08-2008, 07:02 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •