Before starting an Electrical installation, there are some important procedures to carryout.
There should be a detailed Electrical Wiring Diagram to start with. This is normally prepared by an Electrical Engineer.
First he calculates the Electrical Loads, Currents, Cable sizes and the Protective devices for the Electrical Installation. Once these information are obtained Electrical Drawings based on this information is done on a CAD or by a Draftsman on paper. He incorporates these details into a Diagram with Electrical Symbols and text details so that referring these Electrical Diagrams, the Installer[s] can carry out the installation job.
Based on this information, the quantities of material and components needed for the job also is worked out.
There are specifications for carrying out Electrical Installation Work so that the completed installation will abide to rules and regulations of the Electrical Industry.
One needs to be familiar with Electrical Symbols appearing in Electrical Drawings .These symbols can be different from a region to region so one has to be familiar with the symbols used in that part of the world he is living.
The Electrical Wiring Diagram will indicate the areas or locations of a building where Lighting, Socket Outlets [receptacles], Small Appliances or other machinery will be positioned.
The Electrical Conductors [ cables or wires ] needed to be selected according to the Current rating [ Capacity] and Voltage Drop when the rated current flows in the conductors. This selection of the conductor is called Conductor Sizing.
The conductors can be of Copper or Aluminum. Copper is the material used mostly for indoor installations and Aluminum for mostly Power Transmission.
The outer Insulation of the conductors are selected according to the Temperature ,the conductors are used for when carrying current.
There are cables for heavy duty activities such as laid under soil in trenches which are called Armoured cables.
The over current protection for conductors are very important and there are Fuses and Circuit Breakers incorporated to safeguard current carrying conductors.
Ground Fault Circuit Interrupters or Earth Leakage Circuit Breakers
or Residual Current Circuit Breakers will safeguard people from getting Electric
Shock from Live or Hot Circuit conductors or equipment.