F-F-320C
d. A means of adjustment for maintenance of the required secondary output under conditions
of variable line voltage and loading.
e. All necessary high voltage cables and connectors.
A safety switch interlock system(s) shall also be provided to automatically deenergize the
equipment when any access door or access panel of the filter enclosure or power pack is opened.
The system shall also prevent opening of such doors or panels until the equipment has been
deenergized. Each power pack shall be enclosed in a sheet metal housing and shall be
conspicuously labeled to indicate high voltage. High voltage warning signs for filter access doors
and panels shall also be furnished with each unit.
3.8.3.1 Primary power circuits. Primary power circuits shall not be directly grounded. When
capacitive type of grounding is necessary, such capacitance shall be as small as practicable. Leads
from primary power source supplies shall be individually protected against damaging overload
between the service connection and any other part of the system, equipment, or unit, as
applicable.
3.8.3.2 Overload protection. Protective devices shall be provided within the equipment for
primary circuits and such other circuits as required for protection of the equipment from damage
due to conditions such as overload and heating due to dirt and humidity. All parts which are
likely to carry overload, due to dirt or excessive humidity, shall be designed to withstand the
overload. Where this is impracticable, circuit breakers, relays, fuses, or other devices shall be
included to protect the affected parts. The use of secondary protective devices shall be held to a
minimum consistent with good engineering practice.
3.8.3.3 Wiring. Wiring, conductors, conduit, control enclosures, and other components of the
equipment's electrical system shall conform to and be installed in accordance with provisions of
NFPA 70.
3.8.3.4 Power characteristics. Unless otherwise specified (see 6.2), the units shall be designed
for operation on a nominal 115-volt, 60-hertz, power supply.
3.9 After-filters. Each unit shall be equipped with permanent, panel-type filters; disposable, roll-
type filters; or disposable, extended media-type filters in accordance with the specified type and
style of filter unit.
3.9.1 Panel-type filters. Type I and type II units shall be equipped with after-filters which shall
also serve as spray eliminators during the washing cycle. The after-filters shall be of the
permanent, cleanable type, and shall be constructed with corrosion-resistant metal frames and
media.
3.9.2 Roll-type filters. The media for roll-type filters shall be progressively dense glass fibers
having a nominal thickness during exposure to the airstream of not less than 0.50-inch
(12.7 mm). The media shall be reinforced on the air-leaving side by a wire or scrim backing to
prevent necking and shedding. The media shall be charged with an adhesive which will not flow
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