2.7.2
Construction
Motor short-circuit protector bodies shall be constructed of high
temperature, dimensionally stable, long life, nonhygroscopic materials.
Protectors shall fit special MSCP mounting clips and shall not be
interchangeable with any commercially available fuses. Protectors shall
have 100 percent one-way interchangeability within the A-Y letter
designations. All ratings shall be clearly visible.
2.7.3
Ratings
Voltage ratings shall be not less than the applicable circuit voltage.
Letter designations shall be A through Y for motor controller Sizes 0, 1,
2, 3, 4, and 5, with 100,000 amperes interrupting capacity rating. Letter
designations shall correspond to controller sizes as follows:
CONTROLLER SIZE
MSCP DESIGNATION
NEMA 0
A-N
NEMA 1
A-P
NEMA 2
A-S
NEMA 3
A-U
NEMA 4
A-W
NEMA 5
A-Y
2.8
MOLDED-CASE CIRCUIT BREAKERS
2.8.1
General
Molded-case circuit breakers shall conform to NEMA AB 1 and UL 489.
Circuit breakers may be installed in panelboards, switchboards, enclosures,
motor control centers, or combination motor controllers. Circuit breakers
and circuit breaker enclosures located in hazardous (classified) areas
shall conform to UL 877.
2.8.2
Construction
Molded-case circuit breakers shall be assembled as an integral unit in a
supporting and enclosing housing of glass reinforced insulating material
providing high dielectric strength. Circuit breakers shall be suitable for
mounting and operating in any position. Lugs shall be listed for [copper
conductors only] [copper and aluminum conductors] in accordance with UL 486E.
Single-pole circuit breakers shall be full module size with not more than
one pole per module. Multi-pole circuit breakers shall be of the
common-trip type having a single operating handle such that an overload or
short circuit on any one pole will result in all poles opening
simultaneously. Sizes of 100 amperes or less may consist of single-pole
breakers permanently factory assembled into a multi-pole unit having an
internal, mechanical, nontamperable common-trip mechanism and external
handle ties. All circuit breakers shall have a quick-make, quick-break
overcenter toggle-type mechanism, and the handle mechanism shall be
trip-free to prevent holding the contacts closed against a short-circuit or
sustained overload. All circuit breaker handles shall assume a position
between "ON" and "OFF" when tripped automatically. All ratings shall be
SECTION 16475A
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