Armoured Cable - Ground

Discussion in 'Electrical Forum discussion & Blog' started by chefwong, Mar 27, 2014.

  1. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    The AC on the cable serves as the ground in my house circuit runs. Steel boxes-mc/bx cable.

    I'm looking at the wire run that the spark did for our HVAC. Ran flex to a J Box. 3 Wires *2 hots, 1 neutral*. Than ran pipe to the HVAC. Spliced/Extended the wires in the J Box and added a ground terminal in here and added a ground in the conduit leading to the HVAC.


    I don't really run conduit much.
    I'm adding a sub panel off my main panel.
    Plan to connect the 2 via Flex and just the standard Squeeze Flex Connectors on the Sub Panel.
    No need to run a seperate ground, ground bushing, etc etc right ?
  2. Stuff

    Stuff Member

    Messages:
    51
    Location:
    Pennsylvania
    Regular flex conduit can be used as ground up to 6 feet and 20 amp or less only.
    Last edited: Mar 27, 2014
  3. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    Interesting...The spark than ran it to the J Box, I would estimate a good 15-18 feet. Then from the J Box leading down to the HVAC.....another 20-25 feet from there,
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,488
    Location:
    Cave Creek, Arizona
    Because fo the way the armored cable connects to the boxes, it CAN be a 'high resistance' connection and not a very good conductor for a grounding circuit. In fact, given that the panel box is painted, the meta covering l may only be making "marginal" contact with the bare metal as the connector is fastened to it.
  5. ActionDave

    ActionDave Electrician

    Messages:
    345
    Location:
    Colorado
    That's fine, AC cable has a wire in the sheathe that shorts the coils to make it a proper equipment ground. BX is a brand name AC cable. MC is different, it has a green insulated wire in it for equipment grounding.

    What size wires? What kind of flex? What kind of pipe/conduit? What are the distances in each segment?


    You need an equipment ground/green in the flex. You don't need ground bushings.
  6. chefwong

    chefwong New Member

    Messages:
    710
    Location:
    District of Columbia
    I was planning to add a ground wire, but then I was looking at how the sparky ran the HVAC - and I was like , well, if the flex is good enough for the pro, then why do I need to pull the ground for this .

    For the HVAC, the run looks like this
    Main Panel - Flex Run to J Box. 6AWG - 2 Hots and a Neutral ( I did not check but it looks to be ALU flex)

    J Box - added a ground ring to J Box and added a ground wire
    The length from J Box to HVAC is about 25 feet or so
    Last edited: Mar 28, 2014
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