A new regulation has come out that means SPD's are to be used. They are quite expensive so not all clients and Electricians are happy with spending the money on them. They are used to protect equipment from surges in the power supply. This installation was designed for a home network with I.T devices to protect. Wylex offer a nicely designed SPD that has removable cartridges following a surge. This allows end users to easily maintain their protection following a surge.