My Friend can replace light fitting for me, should i do it? To perform any electrical work you need to have licenced electrician, and they know what they are doing and can detect any problem that has been occuring which you were not aware of it? Only work carried out by licenced electrician are covered my Insurance. What is RCD? It's a Residual Current Device or Safety Switch and it provides a fast power cut-off in problem situations. Protecting people and livestocks. What is test & tagging? For the safe operation of electrical appliances, licenced electrician or certified tester will check your appliance electronically and visual inspection. So they are safe to operated