Transfer switch

A transfer switch is switching equipment that transfers a load, selected circuits or a backup arrangement from one supply to another. In home battery and solar backup contexts, the term usually points to manual or automatic switching between the normal grid supply and an alternative supply such as a battery inverter's backup or EPS output. UK storage documents may describe the same grid-separation role with wording such as changeover switch, isolation relay or changeover relay. The transfer has to keep the backed-up part of the installation separated from the grid when it is being supplied in island mode. A transfer switch does not create backup capability by itself: the usable supply still depends on the inverter output, battery state of charge, earthing and protection arrangement, circuit design and loads connected at the time.