UFC 3-535-01
17 November 2005
requirements. It is recommended to review the checklist for vault contained in Chapter
14.
12-1.8.10
Short Circuit Analysis
Perform a short circuit analysis as part of design (to enhance reliability and safety).
Short circuit analysis should comply with: NEC Section 110-9, Section 110-10 and
Section 110-12; and FAA Order 6950.27. Include in the analysis critical points such as:
12.1.8.10.1 Service entrance.
12.1.8.10.2 Switchboards and panelboards.
12.1.8.10.3 Transformer's primary and secondary.
12.1.8.10.4 Transfer switches.
12.1.8.10.5 Load centers.
12.1.8.10.6 Fusible disconnects.
12-1.9
Emergency Power
Provide an emergency generator or other independent power source at each vault
which services systems requiring standby power for continuous operation if the principal
power source fails:
12-1.9.1
Engine Generator (E/G)
Where engine generators are installed, provide a separate room or shelter with
independent ventilation. Make provision for engine exhaust to the exterior of the shelter.
Mufflers may be installed inside or outside the building. If installed inside, they must be
insulated. Engine cooling may be provided by externally-mounted radiators or by use of
a radiator duct to an external exhaust louver. Make provisions for mounting and cooling
resistive load banks for diesel engine testing if the station load is inadequate or cannot
be made available for engine testing. Provide fuel storage capacity for 72 hours of
uninterrupted operation of the standby power system. Also provide automatic starting
and switching capable of supplying the rated load within 15 seconds of a power failure
except where Category II instrument operations are conducted. During Category II
instrument operations, a one-second power transfer is required. This is normally done
by providing a remote start capability which permits operation of the lighting systems on
the engine generator during Category II weather conditions. Standby power availability
is then subject only to switching time. The actual procedure used must be locally
coordinated. See FAA Advisory Circular 150/5340-17, Standby Power for Non-FAA
Airport Lighting Systems, for additional information. Provide an automatic battery
charger for the starting batteries. Isolate the E/G foundation slab to reduce vibration and
noise transmission to other parts of the vault. Comply with the requirements of the NEC,
OSHA and local jurisdictions for emergency power.
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