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Thread: Messenger cable grounding question

  1. #1
    Join Date
    Apr 2007
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    3

    Messenger cable grounding question

    Hi,

    Our church recently added some additional parking lights. They'll be running a 20amp/120volt #6 triplex between 3 poles. On the first pole there will be a switch disconnect for the entire series. From the breaker panel to the disconnect, the wiring will be a hot, neutral and ground, in conduit underground. From the disconnect, 2 insulated conductor (hot and neutral) will go up to the lights. This is because lights are designed in a plastic enclosure and a ground is not required for them. My question is the messenger cable need to be grounded? Rule 396.60 requires messenger cables to be grounded, however there exceptions in Rule 250.86 which state no messenger cable is required when:
    Code:
    (1) Do not provide an equipment ground
    (2) Are in runs of less than 7.5 m (25 ft) our distance is greater than 25 feet
    (3) Are free from probable contact with ground, grounded
    metal, metal lath, or other conductive material
    (4) Are guarded against contact by persons
    Question 2:
    For splice pigtails from lights, there will be a split bolt used and then insulated with rubber tape. Is this enough or is something else required? What is the best type of wire to use from pigtails to the main line?
    Or perhaps someone has a better suggestion on how to set this up?

    Thanks.

  2. #2
    Join Date
    Jul 2004
    Location
    Ca and Wa
    Posts
    1,481
    Quote Originally Posted by aklimok View Post
    Hi,

    Our church recently added some additional parking lights. They'll be running a 20amp/120volt #6 triplex between 3 poles. On the first pole there will be a switch disconnect for the entire series. From the breaker panel to the disconnect, the wiring will be a hot, neutral and ground, in conduit underground. From the disconnect, 2 insulated conductor (hot and neutral) will go up to the lights. This is because lights are designed in a plastic enclosure and a ground is not required for them. My question is the messenger cable need to be grounded? Rule 396.60 requires messenger cables to be grounded, however there exceptions in Rule 250.86 which state no messenger cable is required when:
    Code:
    (1) Do not provide an equipment ground
    (2) Are in runs of less than 7.5 m (25 ft) our distance is greater than 25 feet
    (3) Are free from probable contact with ground, grounded
    metal, metal lath, or other conductive material
    (4) Are guarded against contact by persons
    Question 2:
    For splice pigtails from lights, there will be a split bolt used and then insulated with rubber tape. Is this enough or is something else required? What is the best type of wire to use from pigtails to the main line?
    Or perhaps someone has a better suggestion on how to set this up?

    Thanks.
    I am not sure where the messenger cable comes into play from your description if everything is underground. The bonding from the EGC is required at every pole j-box to bond the pole and/or if the conduit is PVC. A messenger would normally be associated with an overhead drop in my understanding. rbj
    rbj, Seattle...Safety is a Professional Courtesy.

  3. #3
    Join Date
    Apr 2007
    Posts
    3
    Sorry, this will be an overhead run. The messenger cable will support the wires from pole to pole.

  4. #4
    Join Date
    Jul 2004
    Location
    Ca and Wa
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    Quote Originally Posted by aklimok View Post
    Sorry, this will be an overhead run. The messenger cable will support the wires from pole to pole.
    OK, so the Triplex messenger cable is a grounding conductor with the phase and grounded return. The messenger grounding cable run (with the phase conductor) needs to be bond connected down to the switch box in a protected raceway. rbj
    Last edited by gndrod; 11-27-09 at 06:39 PM.
    rbj, Seattle...Safety is a Professional Courtesy.

  5. #5
    Join Date
    Jul 2007
    Posts
    20
    I'd ground the messenger anyway, because of the potential for lightning strike.
    You already have the grounded neutral which will act as bait for the lightning bolt, and then conduct all that energy right into the panel. Grounding the messenger cable will tend to have the bolt take that path to earth, hopefullly reducing the damage to all the other electrical gear in the building.

  6. #6
    Join Date
    Feb 2003
    Location
    Bremerton, Washington
    Posts
    6,484
    Regardless of what 250.86 states, 250.134 requires fixed equipment to be bonded.
    And 250.86 is in Part IV which deals with service conductors so does not apply to your application.
    The rules in different parts don't apply unless there is a reference and of course, part I applies to all parts.
    Moderator-Washington State
    Ancora Imparo

  7. #7
    Join Date
    Jul 2006
    Posts
    1,500
    I often wonder why people as "do I need to ground this?" when I'd rather they ask "Any reason -not- to ground this?"

    If the poles are metal with reinforced concrete bases, then wrapping the messenger around the pole will create a path to the earth (and the poles will need bonding). If the poles are wood, I think you'll want a rod to earth the messenger for lighting protection. (not awake enough to crack the book on this).

  8. #8
    Join Date
    Oct 2009
    Location
    Bethlehem, PA
    Posts
    108
    Quote Originally Posted by aklimok View Post
    Or perhaps someone has a better suggestion on how to set this up?
    I would think if you hired a qualified electrician they would be able to answer all your questions on how this project needs to be correctly wired and installed, but that's just my 2 cents worth.
    I must be getting wiser. The more I know the more I know I know nothing.

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