MIL-HDBK-1027/1B
manner as the other HOA switches. After the device is
installed, the computer will interlock these circuits with the
ventilation such that they remain deenergized until after a
preset purge time. The computer will deenergize these circuits
again at the end of the occupied time. The HOA switch should
remain locked in the automatic mode after the device is
installed. Provide a minimum of one HOA switch for each burner
room and crawl space; (two total) for the 19F5 or 19F5A; provide
one for each 19F3 or 19F3B building (four total); (one total)
for the entire 19F1A or 19F1B building. The key operated
feature of this switch should prevent accidental changing of the
position and the key should only be in the possession of the
senior person in the instructor's station. The positions of
this switch function are as follows:
(1) Hand - The fans must be operating for a
preset time of 3 minutes before the power and lighting circuits
noted above can be energized from this position. Prior to the
installation of the trainer device, this position is used to
provide light and power for construction and testing work in the
crawl space. After installation of the trainer, this position
can be used to provide utilities for normal maintenance work or
to provide power and lighting in the event of a computer
malfunction.
(2)
Off - Power and lighting circuits
deenergized.
(3) Automatic - The computer starts the purge
cycle by operation of the ventilation fans and checks the
sensors in the crawl space and central cabinets containing
propane piping prior to energizing the power and lighting
circuits. Exact sequence and timing of this operation is
completed by NAVAIRWARCEN Training Systems Division at the time
the trainer device and the computer are installed. The switch
will then be locked in the automatic position.
b) Crawl space should contain propane burners,
piping, valves, and regulators. As discussed above, the
ventilation system will be interlocked with the main propane
valve. Propane will not be introduced to the trainer until the
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