About Changeover Switches
A changeover switch is used extensively in industrial applications such as for switching between parallel power supplies or control circuits. Changeover switches are also used in domestic environments. Their primary use is for connecting a generator to power your home in the event of a blackout, or for connecting and disconnecting an external power supply to your caravan.
If connecting an auxiliary supply such as a generator to a domestic consumer unit during a power cut, it is absolutely essential that the building is first completely disconnected from the grid supply. Otherwise it could prove to be hazardous. When correctly wired, a changeover switch allows for the safe connection of an alternative supply while simultaneously disconnecting from the electricity network.
Any switch used for changing between power supplies must be of the break-before-make type. This introduces a break to the circuit when switching so it is not possible to connect two power supplies together. Some changeover switches have a dedicated OFF position between the two feed positions through which the switch must pass for added safety.
Is it essential that a qualified electrician fits a changeover switch. In a domestic application it may be necessary to cut into walls or floors to access and reroute the incoming cable into which the switch must be connected. An ingress protected or waterproof connection socket for the generator must be affixed to the exterior of the building and a local earthing spike will need to be driven in. Be sure to budget for these materials and obtain a professional quote for all work.