Page 1 of 2 12 LastLast
Results 1 to 10 of 19

Thread: NEC Service Definition

  1. #1
    Join Date
    Sep 2003
    Posts
    151

    NEC Service Definition

    I need some help. In 1999 code, service is defined as "from the serving utility." Service equipment is defined as connected to the service conductors. If an owner has 12kv service and their own outdoor 12KV to 480V transformer, then the building does not have service entrance equipment in it and article 250-24, for building services, does not apply, right! At least this is what a site engineer is telling me. If someone else has run into this,does NFPA define a priviate transformer as a private serving utility, or do you need to somehow use the definitions for a separately derived system. The site's transformer for this building sets 700' away and this guy does not want to bond the neutral to the building grounding electrode, which will definitely cause someone to draw a pretty good spark from the elevated neutral voltage.

  2. #2
    Join Date
    Feb 2003
    Location
    Cleveland, Ohio
    Posts
    1,321

    Re: NEC Service Definition

    Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
    Tell him "nice try!". Then tell him to read the entire sentence.
    Dave Nix

  3. #3
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    19,434

    Re: NEC Service Definition

    The grounding at the building would be per 250.32(B)(1) or (B)(2). If an EGC is run with the feeder conductors to the building, the neutral is not permitted to be bonded to the building grounding electrode system. If an EGC is not run with the feeders, then the neutral must be bonded. I don't understand why the neutral voltage would be elevated at the building without the bond. The voltage to earth from the neutral at the building would be equal to the voltage drop on the neutral conductor between the transformer and the building.
    Don
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  4. #4
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    19,434

    Re: NEC Service Definition

    Dave,
    In my opinion this is not a service, it is a feeder. Look at the definition of premises wiring system. The premises wiring starts at the service point.
    Don
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  5. #5
    Join Date
    Feb 2003
    Location
    Cleveland, Ohio
    Posts
    1,321

    Re: NEC Service Definition

    Don,

    You're right. I just couldn't resist!


    Sounds like a crazy idea to me!

    I would also look at 250-30. Grounding Separately Derived Alternating-Current Systems.
    Dave Nix

  6. #6
    Join Date
    Feb 2003
    Location
    Cleveland, Ohio
    Posts
    1,321

    Re: NEC Service Definition

    Say...... This sounds kind of familiar.... doesn't it?

    250-32. Two or More Buildings or Structures Supplied from a Common Service
    (a) Grounding Electrode. Where two or more buildings or structures are supplied from a common ac service by a feeder(s) or branch circuit(s), the grounding electrode(s) required in Part C of this article at each building or structure shall be connected in the manner specified in (b) or (c). Where there are no existing grounding electrodes, the grounding electrode(s) required in Part C of this article shall be installed.
    Dave Nix

  7. #7
    Join Date
    Feb 2003
    Location
    Cleveland, Ohio
    Posts
    1,321

    Re: NEC Service Definition

    "Service equipment is defined as connected to the service conductors."

    Not quite.

    Service Conductors. The conductors from the service point to the service disconnecting means.

    Service Equipment. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.

    Service-Entrance Conductors, Underground System. The service conductors between the terminals of the service equipment and the point of connection to the service lateral.

    Service Lateral. The underground service conductors between the street main, including any risers at a pole or other structure or from transformers, and the first point of connection to the service-entrance conductors in a terminal box or meter or other enclosure, inside or outside the building wall. Where there is no terminal box, meter, or other enclosure, the point of connection shall be considered to be the point of entrance of the service conductors into the building.

    Service Point. The point of connection between the facilities of the serving utility and the premises wiring.
    "....then the building does not have service entrance equipment in it.... "

    Not true.
    Dave Nix

  8. #8
    Join Date
    Sep 2003
    Posts
    151

    Re: NEC Service Definition

    Thanks so far, I think Dave is the closest. The service entrance conductors are 12kv and the service disconnect is at least 1 mile away, it's a huge site. Service equipment is defined as being connected to the load end of the service conductors to a building or structure for the main cut off of the supply. This is at 12 KV. The only thing I can find is that 230 states that "A building served shall be supplied by only one SERVICE unless otherwise permitted. Service conductors and equipment extend from the utility to the "wiring of the premises served". Premisises wiring is defined as interior and exterior wiring from the utility OR transformer. Maybe this is the code writer's out? I should be happy, if it's not a service, then I don't need to supply a service disconnect!

  9. #9
    Join Date
    Feb 2003
    Location
    Illinois
    Posts
    19,434

    Re: NEC Service Definition

    This is not a service and you do not need a service disconnect, but you do need a building disconenct per 225.31 through .33. This is very common type of installation in for industrial and campus type installations. 240.21(C)(4) was added to the code just for this type of installation. Under codes prior to the addition of this section, if the transformer was customer owned, the secondary conductors were required to have overcurrent protection at the transformer. The code change permitted customer owned distribution to follow almost the same rules as a utility service.
    The only difference here is the bonding issue. If the feeder raceway is non-metallic and no EGC is provided this installation would be idential to a utility service. If an EGC is provided the required bonding of the neutral conductor is permitted only at a single location.
    Don
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  10. #10
    Join Date
    Sep 2003
    Posts
    151

    Re: NEC Service Definition

    Thanks Don, the issue becomes that the serving transformer is about 700 feet away and the site only wants a ground at the transformer and not to bond the neutral to the ground electrode. Without this bond, the neutral in that distance becomes a problem. If the building does not have "service disconnect," then article 250 requirements for the second ground and some other things are out the window. Do you agree with the definition of "service," that it is the conductors and EQUIPMENT from the utility to the premises and that "premises wiring" connects to the service point? Would the service point then be the service equipment?

Posting Permissions

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