20 Oct 89
fire protection requirements for single-phase or polyphase outdoor
Buildings located 25 ft (8 m) or more from an oil--cooled transformer do not
require fire exposure protection. Buildings within 25 ft (8 m) of a
transformer require exposure protection by one of the following method.:
a) Protect transformers with a permanently piped water spray system.
b) Where transformers expose only one building of masonry or
concrete construction, the following safeguards shall be provided where
(1) There shall be no window openings in first story walls
within a horizontal distance of 10 ft (3 m) from the transformers. Existing
window opening. shall be closed using brick or concrete block.
(2) Window openings in the first story beyond 10 ft (3 m) and up
to 25 ft (8 m) horizontally from the transformers shall be protected, using
either wired--glass in steel sash or glass block.
(3) Window openings in second and third story walls directly
above the transformers shall be protected using either wired-glass in steel
sash or glass block.
Overhanging eaves, where they exist, shall be fireproof.
c) Where transformers must expose a building having walls other than
masonry or concrete, the following safeguards shall be taken:
(1) Provide a masonry or concrete barrier between building and
transformers, with wing walls at each end of the barrier. The barrier shall
extend at least 1 ft (300 ) above the top of transformer bushings and
pressure--relief vents. The wing walls shall be of the same height and shall
extend horizontally 2 to 3 ft (600 to 900 mm) beyond the transformers,
including any radiators and tap--changer enclosures. At multistory buildings,
provide a fire--resistive roof on this three--aided transformer enclosure.
d) Where transformers expose more than one building, such as
transformers located in courts or angles between buildings or where yard space
is limited, they shall be enclosed in a suitable fire--resistive vault and
protected as shown in Table 8.
e) Where transformers are located on or above noncombustible roofs,
suitable curbed and drained concrete mats or welded steel pans shall be under-
neath units and located so as not to expose roof structures. Oil-filled
transformers shall not be installed on combustible roofs.
f) Oil--insulated transformers installed indoors shall be located in
fire resistive vaults except for indoor transformer installations exempted by
NFPA 70, National Electrical Code. Fire protection shall be provided in
accordance with Table 8. Requirements apply to single-phase or polyphase