g.
Conductors. Power conductors smaller than No. 12 AWG must not be
installed inside the chambers. Aluminum conductors shall not be used.
Conductors smaller than No. 12 AWG may be used for communication and signal
wiring.
h.
Wiring Devices. All switches, relays, outlets, contactors, and
other devices which have make-break contacts must not be installed inside the
chambers. Motors, fans, hoists, and other electrically-powered equipment
must not be installed inside the chambers.
i.
Overcurrent Protection. All power circuits and low-voltage
circuits must have properly sized overcurrent protective devices located
outside the chambers and near the chambers.
3.
GROUNDING.
a.
Chamber. Each chamber must be connected by a No. 6 AWG copper
cable to earth ground. This must be separate from the building, power
supply, or other equipment grounds. All metallic equipment inside the
chamber must be connected by ground cables to the chamber.
b.
Electrical Service. The electrical service ground must not be
connected to the chamber. This means that convenience outlet boxes as well
as conduit must be insulated from the chamber.
c.
Electrical Equipment. Electrical equipment in the chamber,
including communication equipment and instrument chassis must not be
connected electrically to the chamber.
Section 4. LIGHTING
1.
LIGHTING OUTSIDE CHAMBERS. Lighting design for areas around hyperbaric
chambers must follow standard lighting design practices in the Lighting
Handbook of the Illuminating Engineering Society (see Reference (17)). The
illumination level for these areas should generally be 20 to 30 footcandles
(FC). Areas containing controls and indicators should have illumination
levels of 75 to 100 FC which may be provided by supplemental light directly
over control panels. Control panel lights must be serviced by the standby
and emergency power supplies in the event of primary power failure.
2.
LIGHTING INSIDE CHAMBERS. One of the major elements of the electrical
system is the chamber lighting. In the past, hyperbaric chambers and
especially recompression chambers have been designed and equipped with
standard submarine navigation lights. See Figure 9-3. This light has a
standard incandescent lamp contained within a pressure resistant envelope and
may utilize AC or DC power. Energy-limiting DC power sources, as shown in
Figure 9-2, have been used. A few chamber fires in the past were attributed
to the lamp heat as the source of ignition in the oxygen-enriched hyperbaric
atmospheres. To eliminate heat and electric power in the chambers, designs
of safer chamber lights have been made using external originating light
sources and light pipe conductors.
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