W-C-375E
3.2 Qualification. Circuit breakers furnished under this specification shall be products that are authorized by the qualifying activity for listing on the applicable qualified products list before award of the contract (see 4.5. and 6.3).
3.3 Material. Material shall be as specified herein. However, when a definite material is not specified, a suitable material shall be used that will enable the circuit breakers to conform to the performance requirements of this specification. Acceptance or approval of any constituent material shall not be construed as a guaranty of the acceptance of the finished product.
3.3.1 Current carrying parts. Current-carrying parts shall be of silver, a silver alloy, copper, a copper alloy, or other metal suitable for the application, however, iron and steel may be used in multimetallic thermal elements.
3.3.2 Restricted material. Flammable or explosive material, or material which can produce toxic or suffocating fumes when the circuit breakers are in service shall not be used in construction of the circuit breakers.
3.3.3 Corrosion. Iron and steel parts, except for thermal elements, magnet-pole faces, hardened and polished parts such as latching surfaces, etc., where such protection is impractical, shall be adequately protected against corrosion.
3.3.4 Dissimilar metals. When dissimilar metals are used in intimate contact with each other, protection against electrolysis and corrosion shall be provided. The use of dissimilar metals in contact, which tend toward active electrolytic corrosion (particularly brass, copper, or steel used in contact with aluminum or aluminum alloy) is not acceptable. However, metal plating or metal spraying of dissimilar base metals - to provide similar or suitable abutting surfaces is permitted. The use of dissimilar metals separated by a suitable insulating material is also permitted. The use of corrosion-resistant steel in contact with cadmium plating shall also be allowed.
3.4 Design and construction. Circuit breakers shall be of the design, construction, and physical dimensions specified (see 3.1), except circuit breakers not covered by specification sheets (see 3.1.1) shall be UL listed or meet the requirements of this specification prior to inclusion into a specification sheet.
3.4.1 Trip elements. An overcurrent trip element shall be provided in each pole. All overcurrent tripping devices, whether interchangeable or noninterchangeable, shall be sealed against tampering.
3.4.2 Trip-free feature. Circuit breakers shall be designed so that the circuit cannot be maintained closed when any pole is carrying overload currents that would normally automatically trip the circuit breaker to the open position.
3.4.3 Trip indication. Circuit breakers shall be designed to provide positive indication of the main contact position.
3.4.4 Interchangeable trips. An interchangeable trip unit shall not be capable of being installed in any frame having a current rating less than that of the trip unit.
3.4.5 Adjustable magnetic trip units. If a circuit breaker has a magnetic means for tripping, in addition to and entirely independent of a time-delay means for tripping which complies with all the calibration requirements of this specification, the magnetic trip may be adjustable, see 3.1. However, circuit breakers not specifically designed for adjustable magnetic trip shall not be adjustable thermally or magnetically without dismantling of the circuit breaker or trip unit or breaking of a seal.
3.4.6 Housings. A circuit breaker shall have an integral housing for all the mechanisms and live parts except the operating handle and the wiring terminals, and shall be manually operable without opening this housing.
3.4.7 Operating handles. An operating handle of conducting material extending into the housing shall be grounded.
3.4.8 Sealing. Any means for sealing shall be such that breaking or removing it will be plainly evident. Paper or cloth may be used as a seal indicator, but shall not be used as a means for holding parts together.
3.4.9 Plug-in design. A plug-in circuit breaker shall be retained on the stabs without depending on the trim or cover of the enclosure.
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