When to Use a Molded Case Switch (MCS) for your Electrical Installation (10/12/2026)

Although an MCS resembles a molded case circuit breaker (MCCB), its primary function is circuit isolation and load switching rather than automatic overcurrent protection.

Article - October 12, 2026 By LarsonElectronics.com

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When to Use a Molded Case Switch (MCS) for your Electrical Installation

A molded case switch (MCS) is an electrical switching device designed to manually or remotely connect and disconnect electrical power to a circuit, equipment assembly or distribution system.

Although an MCS resembles a molded case circuit breaker (MCCB), its primary function is circuit isolation and load switching rather than automatic overcurrent protection.

Applications

An MCS is appropriate when an electrical installation requires a dedicated disconnecting device without duplicating the overcurrent protection already provided upstream. This arrangement can simplify equipment operation and maintenance while maintaining the required protective functions.

MCS devices are also useful when a local disconnect is needed near industrial machinery. Maintenance personnel can use the disconnect to interrupt the power supply before servicing equipment, provided the device is suitable for the load and isolation function. The switch may have an appropriate lockable operating mechanism and be installed so that the required energy-isolation procedure can be completed safely.

Installations and Configurations

Molded case switches are available in several installation configurations, depending on the electrical system, equipment enclosure and maintenance requirements. Fixed-mounted MCS devices are installed directly inside panels. They are commonly used in permanent installations where the disconnecting device remains in a fixed position and is connected to the circuit through bolted or terminal connections.

Panel-mounted and enclosure-mounted MCS devices provide a dedicated disconnect within an electrical cabinet or near the equipment being controlled. An externally operated rotary handle or door-mounted mechanism can allow personnel to switch the device without opening the enclosure, depending on the manufacturer's design and the installation's safety requirements.

Through-door or externally operated configurations use a mechanical linkage between the switch and an operating handle mounted on the enclosure door. This arrangement can improve accessibility and support equipment isolation procedures. Interlocking mechanisms may prevent the enclosure door from opening while the switch is in the ON position, although the specific interlock behavior depends on the device design.