A disconnect switch is a switch which has the capability to interrupt power to an electrical circuit or to a group of electrical circuits. Disconnect switches are used in a wide variety of settings, and are primarily employed as safety devices which deenergize circuits so that people can work on them safely. Electrical safety devices are only as useful as their maintenance and the surrounding safety procedures, and a disconnect switch must be used properly in order to be effective.
One common example of a setting in which such switches are used is in power distribution. A disconnect switch can be used to manage the distribution network, to shift loads across the network, to interrupt power while maintenance occurs, and to turn off an area of the network if a safety threat arises. A disconnect switch is usually used with a lockout tagout system, in which the switch is locked after it is activated so that it cannot be accidentally turned back on, and tagged so that people know who locked the switch, why, and when.
Many electrical systems for structures and businesses also have a disconnect switch. In this case, the switch can be used to stop the supply of power in an emergency, to power down to switch to another mode of power, and to shut down the system for maintenance. Again, lockout systems are strongly recommended so that people do not reintroduce power to the circuit at an inopportune moment. For something like a home electrical system, a lockout system might be as simple as tape holding the switch in the off position and a note explaining what is going on.
Disconnect switches are designed to be manually operated in most cases. Some may require a key or similar failsafe, to confirm that a user really does want to activate the switch. Other systems are used for managing safety concerns, as seen when a spike of power poses a safety threat and the system shuts down automatically. In these cases, people often must wait for the system to reset before they can power back up again.
Numerous companies manufacture disconnect switches for a number of applications. When installing a disconnect switch, it is important to confirm that it is rated for the application in which it will be used. If the switch does not meet the rating requirements, it may pose a safety risk, because it may not be able to handle power management needs appropriately.
By Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.