What is a Disconnect Switch?

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What is a Disconnect Switch?

Disconnect switches (also known as isolator switches, safety switches, and load break switches) are used to isolate electrical circuits by interrupting the flow of electrical current. By quickly stopping the flow of power, disconnect switches allow for emergency shutdowns, switching to alternate power sources, and maintenance.

Disconnect switches are typically composed of an enclosure, wired electrical contacts, and an actuator (handles, shafts, keys, etc.). The enclosure protects the contacts from environmental hazards and also protects users from touching  live circuits. The handle or knob allows users to engage or disengage the contacts without opening the enclosure. For many applications it is recommended to lock the disconnect switch and tag it once it has been activated so that other users do not accidentally turn the switch back on.

Fusible & Non-Fusible Disconnect Switches

The two primary disconnect switch designs are fusible and non-fusible. As the name implies fusible disconnect switches utilize fuses to protect against overcurrent and short circuiting. In contrast non-fusible disconnect switches do not protect against short circuiting and simply switch the electrical flow on or off. Non-fusible disconnect switches are only advised on systems with fault currents of less than 5kA or a dedicated fuse upstream of the safety switch.


Disconnect Switch Applications

Disconnect switches are often used  in power distribution and industrial applications. In power distribution, disconnect switches may be utilized in emergency situations to shutdown the power to a particular area or to switch from one power source to another. In industrial applications disconnect switches may be used to interrupt power to machinery and motors when there is a safety hazard or when repair is needed. In fact, disconnect switches are mandated by the National Electrical Code (NEC) to be used in all industrial and manufacturing facilities.

Disconnect Switch Manufacturers
•Altech Corp
•Eaton Bussmann
•Mersen (Ferraz Shawmut)


Buying Disconnect Switches

bisco industries is proud to offer disconnect switches from all of the manufacturers listed above. In fact, we have recently optimized our web store for the full line of Mersen low-voltage disconnect switches. These Mersen low-voltage safety switches are UL listed and CSA certified and come in fusible and non-fusible styles. Visit biscoind.com to search and filter disconnect switches and request quotes.

Learn More About Disconnect Switches

To learn more about disconnect switches checkout the resources below. As always bisco’s team of local product experts are happy to help and can connect you with skilled electrical engineers. For help contact us here.
Electrical Engineering Stack Exchange
Engineering 360 / IEEE GlobalSpec
ABB Disconnect Switch Catalog
Mersen Disconnect Switch Catalog

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