Draft 11/17/08
Utility transformer issues began surfacing last year with questions of enforcement responsibilities due to utility transformers being placed inside the buildings downtown.
DOI informed us in April that we needed to protect the buildings from the utility equipment as the general statute exemption applied only to the utility equipment and did not prevent compliance for building protections.
Currently we are using FM Global Property Loss Prevention Data Sheet 5-4 as our default criteria. As always we are open to alternate methods and means per the State
Administrative Code. The sheets can be obtained at http://www.fmglobal.com/fmglobalregistration/ .
While interior installation of utilities equipment and venting were previously to be reviewed at the submittal stage the qualifications of inside were modified by new code language in the 2000 IBC draft. Exterior protection requirement details are now being accepted in plan review and if not shown on the plans the set is being labeled with the following.
Mecklenburg County
Code Enforcement Plan Review
All exterior utility transformers must comply with FM Global standards, or equivalent and all compliance details must be provided to inspector prior to installation if not shown on these plans.
Excerpts from NEC
ARTICLE 450 Transformers and Transformer Vaults (Including Secondary Ties)
450.11 Marking.
Each transformer shall be provided with a nameplate giving the name of the manufacturer, rated kilovolt-amperes, frequency, primary and secondary voltage, impedance of transformers 25 kVA and larger, required clearances for transformers with ventilating openings, and the amount and kind of insulating liquid where used. In
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addition, the nameplate of each dry-type transformer shall include the temperature class for the insulation system.
450.23 Less-Flammable Liquid-Insulated Transformers .
Transformers insulated with listed less-flammable liquids that have a fire point of not less than 300°C shall be permitted to be installed in accordance with 450.23(A) or 450.23(B).
(A) Indoor Installations. Indoor installations shall be permitted in accordance with one of the following:
(1) In Type I or Type II buildings, in areas where all of the following requirements are met: a. The transformer is rated 35,000 volts or less. b. No combustible materials are stored. c. A liquid confinement area is provided. d. The installation complies with all restrictions provided for in the listing of the liquid.
(2) With an automatic fire extinguishing system and a liquid confinement area, provided the transformer is rated 35,000 volts or less
(3) In accordance with 450.26
450.24 Nonflammable Fluid-Insulated Transformers .
Transformers insulated with a dielectric fluid identified as nonflammable shall be permitted to be installed indoors or outdoors. Such transformers installed indoors and rated over 35,000 volts shall be installed in a vault. Such transformers installed indoors shall be furnished with a liquid confinement area and a pressure-relief vent. The transformers shall be furnished with a means for absorbing any gases generated by arcing inside the tank, or the pressure-relief vent shall be connected to a chimney or flue that will carry such gases to an environmentally safe area.
FPN: Safety may be increased if fire hazard analyses are performed for such transformer installations.
For the purposes of this section, a nonflammable dielectric fluid is one that does not have a flash point or fire point and is not flammable in air.
450.26 Oil -Insulated Transformers Installed Indoors .
Oil-insulated transformers installed indoors shall be installed in a vault constructed as specified in Part III of this article.
450.27 Oil-Insulated Transformers Installed Outdoors .
Combustible material, combustible buildings, and parts of buildings, fire escapes, and door and window openings shall be safeguarded from fires originating in oil-insulated transformers installed on roofs, attached to or adjacent to a building or combustible material.
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In cases where the transformer installation presents a fire hazard, one or more of the following safeguards shall be applied according to the degree of hazard involved:
(1) Space separations
(2) Fire-resistant barriers
(3) Automatic fire suppression systems
(4) Enclosures that confine the oil of a ruptured transformer tank
Oil enclosures shall be permitted to consist of fire-resistant dikes, curbed areas or basins, or trenches filled with coarse, crushed stone. Oil enclosures shall be provided with trapped drains where the exposure and the quantity of oil involved are such that removal of oil is important.
FPN: For additional information on transformers installed on poles or structures or under ground, see ANSI C2-2002, National Electrical Safety Code.
450.28 Modification of Transformers.
When modifications are made to a transformer in an existing installation that change the type of the transformer with respect to Part II of this article, such transformer shall be marked to show the type of insulating liquid installed, and the modified transformer installation shall comply with the applicable requirements for that type of transformer.
III. Transformer Vaults
450.41 Location.
Vaults shall be located where they can be ventilated to the outside air without using flues or ducts wherever such an arrangement is practicable.
450.42 Walls, Roofs, and Floors.
The walls and roofs of vaults shall be constructed of materials that have adequate structural strength for the conditions with a minimum fire resistance of 3 hours. The floors of vaults in contact with the earth shall be of concrete that is not less than 100 mm
(4 in.) thick, but where the vault is constructed with a vacant space or other stories below it, the floor shall have adequate structural strength for the load imposed thereon and a minimum fire resistance of 3 hours. For the purposes of this section, studs and wallboard construction shall not be acceptable.
Exception: Where transformers are protected with automatic sprinkler, water spray, carbon dioxide, or halon, construction of 1-hour rating shall be permitted.
FPN No. 1: For additional information, see ANSI/ASTM E119-1995, Method for Fire
Tests of Building Construction and Materials, and NFPA 251-1999, Standard Methods of
Tests of Fire Endurance of Building Construction and Materials.
FPN No. 2: A typical 3-hour construction is 150 mm (6 in.) thick reinforced concrete.
450.43 Doorways.
Vault doorways shall be protected in accordance with 450.43(A), (B), and (C).
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(A) Type of Door. Each doorway leading into a vault from the building interior shall be provided with a tight-fitting door that has a minimum fire rating of 3 hours. The authority having jurisdiction shall be permitted to require such a door for an exterior wall opening where conditions warrant.
Exception: Where transformers are protected with automatic sprinkler, water spray, carbon dioxide, or halon, construction of 1-hour rating shall be permitted.
FPN: For additional information, see NFPA 80-1999, Standard for Fire Doors and Fire
Windows.
(B) Sills. A door sill or curb that is of sufficient height to confine the oil from the largest transformer within the vault shall be provided, and in no case shall the height be less than
100 mm (4 in.).
(C) Locks. Doors shall be equipped with locks, and doors shall be kept locked, access being allowed only to qualified persons. Personnel doors shall swing out and be equipped with panic bars, pressure plates, or other devices that are normally latched but open under simple pressure.
450.45 Ventilation Openings .
Where required by 450.9, openings for ventilation shall be provided in accordance with
450.45(A) through 450.45(F).
(A) Location. Ventilation openings shall be located as far as possible from doors, windows, fire escapes, and combustible material.
(B) Arrangement. A vault ventilated by natural circulation of air shall be permitted to have roughly half of the total area of openings required for ventilation in one or more openings near the floor and the remainder in one or more openings in the roof or in the sidewalls near the roof, or all of the area required for ventilation shall be permitted in one or more openings in or near the roof.
(C) Size. For a vault ventilated by natural circulation of air to an outdoor area, the combined net area of all ventilating openings, after deducting the area occupied by screens, gratings, or louvers, shall not be less than 1900 mm2 (3 in.2) per kVA of transformer capacity in service, and in no case shall the net area be less than 0.1 m2 (1 ft2) for any capacity under 50 kVA.
(D) Covering. Ventilation openings shall be covered with durable gratings, screens, or louvers, according to the treatment required in order to avoid unsafe conditions.
(E) Dampers. All ventilation openings to the indoors shall be provided with automatic closing fire dampers that operate in response to a vault fire. Such dampers shall possess a standard fire rating of not less than 1½ hours.
FPN: See ANSI/UL 555-1995, Standard for Fire Dampers.
(F) Ducts. Ventilating ducts shall be constructed of fire-resistant material.
450.46 Drainage.
Where practicable, vaults containing more than 100 kVA transformer capacity shall be provided with a drain or other means that will carry off any accumulation of oil or water
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in the vault unless local conditions make this impracticable. The floor shall be pitched to the drain where provided.
450.47 Water Pipes and Accessories.
Any pipe or duct system foreign to the electrical installation shall not enter or pass through a transformer vault. Piping or other facilities provided for vault fire protection, or for transformer cooling, shall not be considered foreign to the electrical installation.
450.48 Storage in Vaults.
Materials shall not be stored in transformer vaults.
Excerpts from FM Global
2.1.2.1 Transformers should be installed, operated and maintained in accordance with manufacturers’ recommendations.
2.2.1.1.1 Indoor transformers should be located a minimum of 3 ft (0.9 m) from building walls
2.2.1.2.3 Transformer rooms should be located on an outside wall where possible.
2.2.1.3.2 Oil Insulated Transformers
Transformers should be located within a room of fire resistant construction. The fire resistance of the construction depends on the quantity of insulating liquid in the largest transformer. Transformer rooms should be located on an outside wall of the building where possible.
2.3 Outdoor Transformers
The following protection recommendations are based on whether the transformer is FM Approved or equivalent, and the volume and type of insulating liquid used.
Outdoor transformers may be located on or adjacent to buildings as often happens with generating station transformers and distribution transformers at manufacturing plants. They may also be located in remote areas such as substations.
2.3.1 Construction and Location
2.3.1.1 Exposure Protection
Buildings or equipment exposed by transformers should be protected by separation, a fire barrier or a water spray system on the transformers.
2.3.1.1.1 Separation Distance
2.3.1.1.1.1 The separation distance between buildings and transformers should be as indicated in Table 2a. Horizontal distance is measured from the transformer if an FM Approved less flammable fluid is used. Horizontal distance is also measured from the transformer where unapproved fluids or mineral oil filled transformers less than 500 gal (1.9 m3) are used and the ground slopes away from the transformer. If the transformer contains an unapproved fluid or mineral oil of 500 gal (1.9 m3) or more the distance is measured from the dike
(see Fig. 3).
2.3.1.1.1.2 The separation distance between other equipment (including adjacent transformers) should be as indicated in Table 2b.
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2.3.1.1.2 Fire Barriers
2.3.1.1.2.1 Buildings
2.3.1.1.2.1.1 Where building walls are used for protection, the exposed wall should extend the horizontal and vertical distances from the dike or transformer specified in Table 2a.
2.3.1.1.2.1.2 Roofs exposed by mineral oil insulated transformers should be
Class A rated for the exposed area. The exposed area is considered to be the following: a) 15 ft (4.6 m) from a transformer containing 1,000 to 5,000 gal (3.8 to 19 m3) of mineral oil where roofs are less than 25 ft (7.76 m) high. b) 25 ft (7.6 m) from a transformer containing in excess of 5,000 gal (19 m3), where roofs are less than 50 ft high.
2.3.1.1.2.2 Equipment
2.3.1.1.2.2.1 For equipment protection, barriers should extend 1 ft (0.3 m) vertically and 2 ft (0.6 m) horizontally beyond transformer components that could be pressurized as the result of an electrical fault. This would typically include bushings, pressure relief vents, radiators, tap changer enclosures, etc.
2.3.1.1.2.2.2 Provide barriers of concrete block or reinforced concrete construction adequate for two-hour fire resistance. Fire barriers constructed of other materials may be used provided: (1) all components are capable of withstanding a two-hour fire exposure by an ASTM E-119 test from either side with no flame penetration to the unexposed side, and (2) barriers are capable of withstanding not less than 25% of full design wind loads at maximum fireexposed material temperatures. Use design wind speeds (3-second gust) per DS 1-28, Design Wind Loads , or similar, acting concurrently with the worstcase fire exposure.
2.3.1.2 Containment
2.3.1.2.1 General
2.3.1.2.1.1 Provide a containment system for transformers where: a) a release of mineral oil would expose buildings. b) more than 500 gal (1.9 m3) of mineral oil could be released. c) more than 1320 gal (5 m3) of FM Approved less flammable fluid could be released. d) more than 2,640 gal (10 m3) of biodegradable FM Approved less flammable fluid could be released.
For this purpose: 1) the fluid must be certified as a biodegradable fluid by the government environmental protection agency, 2) a release of the fluid must not expose navigable waterways (see Appendix A for definition) and 3) the transformer must be properly labeled.
2.3.1.2.1.2 The containment system should be large enough for the volume of oil in the largest transformer and the water from a 10-min discharge of the water spray system if provided. If there are three or more transformers, it should be assumed that the fire will occur in the middle transformer and the water spray systems on adjacent transformers will operate.
2.3.1.2.1.3 The containment system should consist of a pit or a diked area and a drainage system for removal of rainwater. The pit should be protected as
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described in 2.3.1.2.2 and 3 if the transformer is mineral oil insulated. It may be unprotected if the transformer contains an FM Approved less flammable fluid.
2.3.1.2.1.4 The pit or diked area should be sized to contain the contents of the largest transformer. The area of the pit should extend as follows: a) For transformers containing 1,000 gal (3.8 m3) or less, the area of the pit should extend 3 ft (0.9 m) beyond oil containing components where curbing is provided and 5 ft (1.5 m) beyond oil containing components where curbing is not provided. b) For transformers containing more than 1,000 gal (3.8 m3), the area of the pit should extend 5 ft (1.5 m) beyond oil containing components where curbing is provided and 8 ft (2.4 m) beyond oil containing components where curbing is not provided.
2.3.1.2.2 Rock-Filled Pits
2.3.1.2.2.1 Where rock-filled pits are used, the rock should be loosened and turned as necessary to prevent filling of void spaces by dirt, dust or silt. The frequency is dependent on area of the country and location near manufacturing facilities which generate dust or flyash.
2.3.1.2.3 Open Pits
2.3.1.2.3.1 Where an open pit is used, one of the following forms of protection should be provided: a) Automatic sprinkler or water spray protection should be provided for the pit area designed to a discharge density of 0.30 gal/min ft2 (15 mm/min) over the area of the pit; or b) A 12-in (30 cm) thick layer of rock located on steel grating should be provided at the top of the pit. The rock used should be 1.5 in. (3.8 cm) washed and uniformly sized rock, (Size No 5, ASTM D448 Standard Classification for Sizes of
Aggregate for Road and Bridge Construction ).
2.3.1.3 Roof-Mounted Transformer Installations
2.3.1.3.1 Containment systems should be provided for roof-mounted transformers. a) For transformers with 500 gal (1.9 m3) or less insulating liquid, the containment system may be a welded steel pan or curbed concrete mat with capacity large enough to handle the liquid in the largest transformer. b) For mineral oil insulated transformers with more than 500 gal (1.9 m3) liquid capacity, containment should be rock-filled or of the open pit design with protection as recommended in Section 2.3.1.2.2 and 2.3.1.2.3. For FM Approved less flammable fluid insulated transformers an open containment may be used. c) Class A roof construction should be used for the horizontal distance from the transformer specified for noncombustible construction in Table 2a.
2.3.1.3.2 The containment system should be drained to a safe location acceptable to the authority having jurisdiction.
2.3.1.3.3 Adjacent buildings and other equipment should be protected in accordance with Section 2.3.1.1.
2.3.2 Protection
2.3.2.1 Water Spray Exposure Protection
2.3.2.1.1 Buildings
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2.3.2.1.1.1 If water spray or automatic sprinkler protection is used for building protection, a discharge density of 0.20 gpm/ft2 (8 mm/min) should be used over the exposed surface.
2.3.2.1.1.2 The water supply should be adequate for 2 hours and should include a hose stream demand of 500 gpm (1900 l/min).
2.3.2.1.2 Equipment
2.3.2.1.2.1 For multiple transformer installations the water spray system should be designed based on simultaneous operation of the water spray systems for the adjacent transformers.
2.3.2.1.2.2 The water spray system should be designed to provide a density of
0.25 gal/min ft2 (10 mm/min) over transformer surfaces, except areas under the transformer in accordance with Data Sheet 4-1N, Water
Spray Fixed Systems .
2.3.2.1.2.3 Where the ground around the transformer is nonabsorbing, water spray should be provided at a density of 0.15 gal/min ft2 (6 mm/min) for the diked area or for a distance of 10 ft (3 m) from the transformer in all directions.
2.3.2.1.2.4 Components of the water spray system, such as piping, spray nozzles, etc. should be a minimum of 18 in. (45.7 cm) from the transformer.
2.3.2.1.2.5 Piping should not pass over the top of the transformer or be exposed by tank relief vents.
2.3.2.1.2.6 Water spray nozzles should not be directed at bushings.
2.3.2.1.2.7 The water supply should be adequate for 1 hour and include a hose stream demand of 250 gpm (950 l/min).
Excerpts from NFPA 850
C.1.1.2 Outdoor Transformers
Combustible material, combustible buildings, door and window openings shall be safeguarded from fires in oil-insulated transformers. Methods of achieving this are space separation, fire resistant barriers, automatic water spray and enclosures to confine oil from a ruptured transformer.
C.1.2
NFPA 850, Fire Protection for Fossil Fueled Steam Electric Generating Plants, contains recommended practices for both indoor and outdoor transformers.
There is no conflict with NFPA 850. This data sheet gives separate distances between transformer and buildings based on the quantity of fluid in the transformer and the type of construction of the building. NFPA 850 assumes that the building construction will be noncombustible (typically insulated metal on steel frame) and gives spacing based on the volume of fluid in the transformer. The separation distances given in this data sheet are the same as those given in NFPA 850 for this type of construction. This data sheet allows separation, barriers or water spray protection to be used to protect transformers.
NFPA 850 recommends that oil-filled main, station service and startup transformers be protected by water spray or foam water systems.
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C.1.2.1 Indoor Transformers
Where oil-filled transformers of greater than 100 gal (380 dm3) oil capacity are installed, they should be separated from adjacent areas by fire barriers of 3 hr fire resistance rating. Where an automatic fire suppression system is provided, the fire barrier rating may be reduced to one hour.
C.1.2.2 Outdoor Transformers
Where transformers are in excess of 500 gal (1.9 m3) oil capacity, a 2-hr-rated fire barrier or space separation is needed to protect adjacent structures including other transformers. The space separation is dependent on the quantity of oil in the transformer. Twenty-five feet (7.6 m) is needed for 500 to 5,000 gal (1.9 to 19 m3); 50 ft (15.2 m) is needed where quantities are in excess of 5,000 gal (19 m3). Where a fire wall is not provided, the edge of the oil spill (dike) must be a minimum of 5 ft (1.5 m) from the exposed structure. In addition, oil-filled main, station service, and startup transformers should be protected by water spray or foam-water systems.
The following are additional transformer issues and department positions
1.
ISSUE - The pits for the padmount transformers and the flat pads are not separated so that the high voltage and low voltage cables are not contained in separate enclosures. This standard does not reflect NEC compliance.
POSITION - A barrier needs to be installed to ensure separation of the systems if the installation is done by the electrical contractor . For a pit, a two inch solid masonry or poured concrete barrier would be acceptable, or a bonded metal divider could be utilized as long as it is of the same character of the divider that is used in the transformers. Other alternatives would be considered by Code
Enforcement as long as they would provide similar separation and physical characteristics. Code Enforcement realizes the need for system bonding and will allow a ¾” PVC sleeve for the concrete or masonry dividers so that the conductor can pass through, the sleeve needs to be sealed after the conductor is installed. For metal dividers a ¾” hole would be provided & sealed for the same purpose. Drainage is required for both sides of the pit.
NEC -300.3 Conductors. (C) Conductors of Different Systems
(2) Over 600 Volts, Nominal. Conductors of circuits rated over 600 volts, nominal, shall not occupy the same equipment wiring enclosure, cable, or raceway with conductors of circuits rated 600 volts, nominal, or less unless otherwise permitted in (C)(2)(a) through (C)(2)(e).
(a) Secondary wiring to electric-discharge lamps of 1000 volts or less, if insulated for the secondary voltage involved, shall be permitted to occupy the same luminaire (fixture), sign, or outline lighting enclosure as the branch-circuit
(b) Primary leads of electric-discharge lamp ballasts insulated for the primary voltage of the ballast, where contained within the individual wiring
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enclosure, shall be permitted to occupy the same luminaire (fixture), sign, or outline lighting enclosure as the branch-circuit conductors.
(c) Excitation, control, relay, and ammeter conductors used in connection with any individual motor or starter shall be permitted to occupy the same enclosure as the motor-circuit conductors.
(d) In motors, switchgear and control assemblies, and similar equipment, conductors of different voltage ratings shall be permitted.
(e) In manholes, if the conductors of each system are permanently and effectively separated from the conductors of the other systems and securely fastened to racks, insulators, or other approved supports, conductors of different voltage ratings shall be permitted.
Conductors having nonshielded insulation and operating at different voltage levels shall not occupy the same enclosure, cable, or raceway.
2. ISSUE – Currently there are non compliant pad/pit installations with regards to separation. How will those be handled?
POSITION – Code Enforcement will only inspect those installations where changes are made and the electrical contractor is installing the secondary .
Since the separation has been required for an extended period of time (NEC 1968) the installations will have to be compliant as outlined in issue 1. Those that were installed non compliant were assumed by Code Enforcement to have the utility point at the building and if so were not compelled to comply with the NEC.
3. ISSUE – Clearances are not being maintained that apply to venting of oil filled transformer vaults.
POSITION – The NEC states that vents shall be as far as possible from building openings and combustibles. Per current policy the default distance is now per FM
Global Property Loss Sheeet 5-4, Table 2a, using the combustible construction colum.
NEC 450.45 Ventilation Openings.
Where required by 450.9, openings for ventilation shall be provided in accordance with 450.45(A) through 450.45(F).
(A) Location. Ventilation openings shall be located as far as possible from doors, windows, fire escapes, and combustible material.
CURRENTLY EXISTING INSTALLATIONS ARE BEING INSPECTED AND
COMPLIANCE JUDGED ON A CASE BY CASE BASIS
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