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450.23 Less-Flammable Liquid-Insulated Transformers
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(A) Indoor Installations
Indoor installations shall be permitted in accordance with one of the following:
- In Type I or Type II buildings, in areas where all of the following requirements are met:
- The transformer is rated 35,000 volts or less.
- No combustible materials are stored.
- A liquid confinement area is provided.
- The installation complies with all the restrictions provided for in the listing of the liquid.
Informational Note: Such restrictions can include, but are not limited to, maximum pressure of the tank, use of a pressure relief valve, appropriate fuse types, and proper sizing of overcurrent protection. - If an automatic fire extinguishing system and a liquid confinement area is present, provided the transformer is rated 35,000 volts or less
- If the installation complies with 450.26
(B) Outdoor Installations
Less-flammable liquid-filled transformers shall be permitted to be installed outdoors, attached to, adjacent to, or on the roof of buildings, if installed in accordance with (1) or (2).
- For Type I and Type II buildings, the installation shall comply with all the restrictions provided for in the listing of the liquid.
Informational Note No. 1: Installations adjacent to combustible material, fire escapes, or door and window openings can require additional safeguards such as those listed in 450.27.Informational Note No. 2: Such restrictions can include, but are not limited to: maximum pressure of the tank, use of a pressure relief valve, appropriate fuse types, and proper sizing of overcurrent protection.
- In accordance with 450.27.
Informational Note No. 1: As used in this section, Type I and Type II buildings refers to Type I and Type II building construction as defined in NFPA 220-2018, Standard on Types of Building Construction. Combustible materials refers to those materials not classified as noncombustible or limited-combustible as defined in NFPA 220-2018, Standard on Types of Building Construction.
Informational Note No. 2: See definition of Listed in Article 100.
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