New Miniature Circuit Breaker for Operation in Buildings

Siemens has developed a new miniature circuit breaker (MCB) with a switching capacity of 10 kilo amperes (kA), which can be used especially in non-residential and industrial buildings.

The 5SL4 miniature circuit breaker safely shuts down circuits in buildings in case of overloads or short circuits and thus protects cables and devices from damage. The MCB with an integrated snap-on fixing system for mounting on the standard mounting rail can be integrated with minimum effort in existing electrical installations and combined with additional devices.

The MCB is compatible with all Siemens accessory components, such as AFD units, auxiliary and residual current operated circuit breakers, undervoltage releases and fault signal contacts, and can thus be expanded by a wide range of functions. In addition to high operational and plant safety, the 5SL4 miniature circuit breakers offer protection and convenience during installation and servicing: The touch protection integrated in the terminals protects the installer from electrical shock when connecting the devices. The colored switch position indicator integrated in the handle always clearly indicates the current switching state. A handle locking device prevents unauthorized switching. Thanks to the consistent busbar concept, all the devices can be quickly and easily fitted in existing electrical installations. With the aid of the latching slide, they can be conveniently mounted on or removed from the standard mounting rail in the junction box. The rectangularly-designed terminals offer space for pin busbars, as well as additional conductors with a surface area of 0.75 to 25 mm².

The new Siemens devices in the 5SL4 series are available with the tripping characteristics B, C and D: The miniature circuit breakers with tripping characteristic B are designed for universal use in socket outlet circuits and lighting circuits. In lamp and motor circuits with higher starting currents, miniature circuit breakers with tripping characteristic C are generally used. For electrical circuits with strong pulse-generating equipment, such as transformers or solenoid valves, switches are used with tripping characteristic D.

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