Results 1 to 5 of 5

Thread: Code Clarification 310.15 (B) (5) (a) Neutral Conductor

  1. #1
    Join Date
    Jan 2009
    Posts
    18

    Code Clarification 310.15 (B) (5) (a) Neutral Conductor

    (5) Neutral Conductor.
    (a) A neutral conductor that carries only the unbalanced
    current from other conductors of the same circuit shall not be
    required to be counted when applying the provisions of
    310.15(B)(3)(a).

    My question is basically when is it called the “SAME CIRCUIT”
    Is this only relevant when it's connected to any single device? i.e. a Panel, ac, appliance?
    Or is it also at any multi wire branch circuit?
    In other words what is the definition of “SAME CIRCUIT”

    This came up at a code refreshing course last night, and it went back and forth
    I would appreciate your input on this

    Thanks all

  2. #2
    Join Date
    Feb 2003
    Location
    Fl
    Posts
    16,823
    It is any Multi Wire Circuit, it could a service or branch circuit.

    Roger
    Moderator

  3. #3
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    34,337
    Two wire circuit - there is no unbalance current - both conductors are current carrying

    Multiwire circuit - some can have only unbalance current on neutral some do not.

    Single phase three wire (such as 120/240) the neutral only carries unbalance current.

    Three phases plus neutral from a wye secondary the neutral only carries unbalance current.

    Two phases plus neutral from a wye secondary the neutral carries about same amount of current as highest loaded phase conductor.

    Having a lot of harmonic producing loads can change this though.

  4. #4
    Join Date
    Feb 2009
    Location
    Durango, CO, 10 h 20 min without traffic from winged horses.
    Posts
    9,011
    Quote Originally Posted by he1029 View Post
    My question is basically when is it called the “SAME CIRCUIT”
    Is this only relevant when it's connected to any single device? i.e. a Panel, ac, appliance?
    Or is it also at any multi wire branch circuit?
    In other words what is the definition of “SAME CIRCUIT”
    A multiwire branch circuit is a circuit. The conductors of a MWBC don't all have to go to the same device for it to be the same circuit.

    You have four wires, A,B,C and a noodle; it doesn't matter how many different lights those conductors go to, the electrons are leaving home and coming back (i.e. completing the circuit) on the same four wires.
    If Billy Idol or John Denver is on your play list go and reevaluate your life.

  5. #5
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    18,623
    Looking at another way, a branch circuit consists of all of the conductor downstream of the branch OCPD.
    If it is not a branch OCPD, all the conductors downstream as far as the next OCPD(s) are a feeder circuit

    Sent from my XT1585 using Tapatalk

Posting Permissions

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