clearly visible.
2.8.3
Ratings
Voltage ratings shall be not less than the applicable circuit voltage. The
interrupting rating of the circuit breakers shall be at least equal to the
available short-circuit current at the line terminals of the circuit
breaker and correspond to the UL listed integrated short-circuit current
rating specified for the panelboards and switchboards. Molded-case circuit
breakers shall have nominal voltage ratings, maximum continuous-current
ratings, and maximum short-circuit interrupting ratings in accordance with
NEMA AB 1. Ratings shall be coordinated with system X/R ratio.
2.8.4
Cascade System Ratings
Circuit breakers used in series combinations shall be in accordance with UL
489. Equipment, such as switchboards and panelboards, which house
series-connected circuit breakers shall be clearly marked accordingly.
Series combinations shall be listed in the UL Recognized Component
Directory under "Circuit Breakers-Series Connected."
2.8.5
Thermal-Magnetic Trip Elements
Thermal magnetic circuit breakers shall be provided as shown. Automatic
operation shall be obtained by means of thermal-magnetic tripping devices
located in each pole providing inverse time delay and instantaneous circuit
protection. The instantaneous magnetic trip shall be adjustable and
accessible from the front of all circuit breakers on frame sizes above
[150] [_____] amperes.
2.8.6
Solid-State Trip Elements
Solid-state circuit breakers shall be provided as shown. All electronics
shall be self-contained and require no external relaying, power supply, or
accessories. Printed circuit cards shall be treated to resist moisture
absorption, fungus growth, and signal leakage. All electronics shall be
housed in an enclosure which provides protection against arcs, magnetic
interference, dust, and other contaminants. Solid-state sensing shall
measure true RMS current with error less than one percent on systems with
distortions through the 13th harmonic. Peak or average actuating devices
are not acceptable. Current sensors shall be toroidal construction,
encased in a plastic housing filled with epoxy to protect against damage
and moisture and shall be integrally mounted on the breaker. Where
indicated on the drawings, circuit breaker frames shall be rated for 100
percent continuous duty. Circuit breakers shall have tripping features as
shown on the drawings and as described below:
a.
Long-time current pick-up, adjustable from 50 percent to 100
percent of continuous current rating.
b.
[Fixed] [Adjustable] long-time delay.
c.
Short-time current pick-up, adjustable from 1.5 to 9 times
long-time current setting.
d.
[Fixed] [Adjustable] short-time delay.
e.
[Short-time I square times t switch.]
SECTION 16475A
Page 17
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