How do you connect surge arrester?

The surge arrestor is clipped onto the rail in the DB next to the existing breakers, the live (red) wire is looped from the existing live loops above the other circuit breakers onto the top of the surge arrestor. The bottom of the arrestor is connected to the earth bar. It would be better to install a seperate earth spike and connect the botom of the arrestor to that to make sure that you have a good earth but it is sometimes not possible if the DB enclosure is indoors.