Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 1K views

    450.27 - NFPA 70 (2017) National Electrical Code® Handbook

    Uploaded by

    vthiyagain
    This document discusses requirements for oil-filled transformers installed outdoors or in vaults to minimize fire hazards. Key points include: 1) When oil-filled transformers are installed outdoors, combustible materials must be protected from fire originating from the transformer. Safeguards like space, barriers, suppression systems, or enclosures are required depending on the hazard level. 2) Transformer vaults must have walls, roofs, and floors with a minimum 3-hour fire resistance rating. Exceptions allow 1-hour if automatic suppression is installed. 3) Vault doors must be tight-fitting with a minimum 3-hour fire rating. Exceptions allow 1-hour if automatic suppression is installed. Doors must be equipped with

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    450.27 - NFPA 70 (2017) National Electrical Code® Handbook

    Uploaded by

    vthiyagain
    1K views1 page
    This document discusses requirements for oil-filled transformers installed outdoors or in vaults to minimize fire hazards. Key points include: 1) When oil-filled transformers are installed outdoors, combustible materials must be protected from fire originating from the transformer. Safeguards like space, barriers, suppression systems, or enclosures are required depending on the hazard level. 2) Transformer vaults must have walls, roofs, and floors with a minimum 3-hour fire resistance rating. Exceptions allow 1-hour if automatic suppression is installed. 3) Vault doors must be tight-fitting with a minimum 3-hour fire rating. Exceptions allow 1-hour if automatic suppression is installed. Doors must be equipped with

    Original Description:

    450.27 Clause NEC 2017

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document discusses requirements for oil-filled transformers installed outdoors or in vaults to minimize fire hazards. Key points include: 1) When oil-filled transformers are installed outdoors, combustible materials must be protected from fire originating from the transformer. Safeguards like space, barriers, suppression systems, or enclosures are required depending on the hazard level. 2) Transformer vaults must have walls, roofs, and floors with a minimum 3-hour fire resistance rating. Exceptions allow 1-hour if automatic suppression is installed. 3) Vault doors must be tight-fitting with a minimum 3-hour fire rating. Exceptions allow 1-hour if automatic suppression is installed. Doors must be equipped with

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    1K views1 page

    450.27 - NFPA 70 (2017) National Electrical Code® Handbook

    Uploaded by

    vthiyagain
    This document discusses requirements for oil-filled transformers installed outdoors or in vaults to minimize fire hazards. Key points include: 1) When oil-filled transformers are installed outdoors, combustible materials must be protected from fire originating from the transformer. Safeguards like space, barriers, suppression systems, or enclosures are required depending on the hazard level. 2) Transformer vaults must have walls, roofs, and floors with a minimum 3-hour fire resistance rating. Exceptions allow 1-hour if automatic suppression is installed. 3) Vault doors must be tight-fitting with a minimum 3-hour fire rating. Exceptions allow 1-hour if automatic suppression is installed. Doors must be equipped with

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 1

    450.

    27 Article 450  ● Transformers and Transformer Vaults (Including Secondary Ties)

    450.27  Oil-Insulated Transformers Installed Outdoors.  imposed thereon and a minimum fire resistance of 3 hours. For
    Combustible material, combustible buildings, and parts of the purposes of this section, studs and wallboard construction
    buildings, fire escapes, and door and window openings shall be shall not be permitted.
    safeguarded from fires originating in oil-insulated transform-
    Exception:  Where transformers are protected with automatic
    ers installed on roofs, attached to or adjacent to a building or
    sprinkler, water spray, carbon dioxide, or halon, construction
    combustible material.
    of 1-hour rating shall be permitted.
    In cases where the transformer installation presents a fire
    hazard, one or more of the following safeguards shall be applied Informational Note No. 1:  For additional information, see ANSI/
    according to the degree of hazard involved: ASTM E119-15, Method for Fire Tests of Building Construction
    and Materials.
    (1) Space separations Informational Note No. 2: A typical 3-hour construction is
    (2) Fire-resistant barriers 150 mm (6 in.) thick reinforced concrete.
    (3) Automatic fire suppression systems Vaults are intended primarily as passive fire protection. The need for
    (4) Enclosures that confine the oil of a ruptured transformer vaults is dictated by the combustibility of the dielectric media and the
    tank size of the transformer. Transformers insulated with mineral oil have the
    Oil enclosures shall be permitted to consist of fire-resistant greatest need for passive protection to prevent the spread of burning oil
    dikes, curbed areas or basins, or trenches filled with coarse, to other combustible materials.
    Although construction of a 3-hour-rated wall may be possible
    crushed stone. Oil enclosures shall be provided with trapped
    using studs and wallboard, this construction method is not permitted
    drains where the exposure and the quantity of oil involved are
    for transformer vaults because of the concern for containing projectiles
    such that removal of oil is important.
    created in a transformer explosion. A reduction in fire resistance rating
    Informational Note:  For additional information on transform- from 3 hours to 1 hour is permitted for vaults equipped with an auto-
    ers installed on poles or structures or under ground, see ANSI matic fire suppression system.
    C2-2007, National Electrical Safety Code.
    See also
    450.28  Modification of Transformers.  When modifications 450.23 and its commentary, which relates to Type I and Type II build-
    are made to a transformer in an existing installation that change ing construction
    the type of the transformer with respect to Part II of this article,
    such transformer shall be marked to show the type of insulat- 450.43 Doorways.  Vault doorways shall be protected in accor-
    ing liquid installed, and the modified transformer installation dance with 450.43(A), (B), and (C).
    shall comply with the applicable requirements for that type of (A)  Type of Door.  Each doorway leading into a vault from the
    E7
    transformer.
    An existing askarel-insulated transformer may have the askarel replaced
    -AF2C-E8840C0B7294
    building interior shall be provided with a tight-fitting door that
    has a minimum fire rating of 3 hours. The authority having juris-
    with either oil or a less flammable liquid. Where such a modification diction shall be permitted to require such a door for an exterior
    takes place, the completed installation must have the same degree of wall opening where conditions warrant.
    safety as a new installation. For example, replacement of askarel with oil Exception:  Where transformers are protected with automatic
    in an indoor installation without a vault may not be acceptable (see sprinkler, water spray, carbon dioxide, or halon, construction
    450.26 and its exceptions). The same is true if the replacement liquid is a
    of 1-hour rating shall be permitted.
    less flammable liquid (see 450.23). Additional safety precautions may be
    necessary to compensate for the different fire characteristics of the new Informational Note:  For additional information, see NFPA 80-2013,
    dielectric fluid. Standard for Fire Doors and Other Opening Protectives.
    (B) Sills. A door sill or curb that is of an approved height that
    Part III.  Transformer Vaults will confine the oil from the largest transformer within the vault
    shall be provided, and in no case shall the height be less than
    450.41 Location.  Vaults shall be located where they can be 100 mm (4 in.).
    ventilated to the outside air without using flues or ducts wherever
    such an arrangement is practicable. (C) Locks. Doors shall be equipped with locks, and doors shall
    be kept locked, access being allowed only to qualified persons.
    450.42  Walls, Roofs, and Floors.  The walls and roofs of vaults Personnel doors shall open in the direction of egress and be
    shall be constructed of materials that have approved structural equipped with listed panic hardware.
    strength for the conditions with a minimum fire resistance of Section 450.43 requires transformer vault doors to be locked but prohib-
    3 hours. The floors of vaults in contact with the earth shall be of its the use of conventional rotation-type door knobs. An injured worker
    concrete that is not less than 100 mm (4 in.) thick, but, where the attempting to escape from a transformer vault may not be able to oper-
    vault is constructed with a vacant space or other stories below ate a rotating-type door knob but would be able to escape through a
    it, the floor shall have approved structural strength for the load door equipped with panic-type hardware.

    562 2017   National Electrical Code Handbook

    You might also like