Wiring ( Introduction )

To the average user the olny important part of the elecricity service is the outlets at which he received electricity . To the engineer concerned with deigning or installing the service , the system of cables which links these outlets to each other and to the supply coming into the building is just as important and perhaps even more so . In practice , the electrical service is a complete interdependent system and the practical engineer thinks of it as a whole , but , as with the teaching of any sucject , one has to break it down into parts in order to explain it in an orderly fashion which will make sense to a student with no previous knowledge of the subject .
  In this chaptr , we shall considr different ways in which cables can be installed in a building . The calculation of the size of particular cables shall leave to chapter 4 and the selection and grouping of outlets to be served by one cable we shall leave to chapter 5 . For this chapter , we assume  that we know where cables are to run and discuss olny how to get them into the bulding.This aspect of the electical service can for convenience be called "method of installation'
  A method of installation consists of talking a suitable type of cable , giving it adequate protection and putting it into the building in some way . The subject can , therefore , be fairly logically considered by considering types of cables , methods of protection and methods of installation . The types of cable available and in general use have been described in Chapter 2 . The protection against mechanical damage given to cale is sometimes part of the cable itself , as with PVC insulated PVC sheathed cables , and sometimes part of the method of installation , as with conduit systems . it can be more confusing than helpful to take a logical scheme if things too rigidly and , rahter than deal with protection in a chapter of its own , we are dealing with it partly in the previous chapter and partly in this , according to whether it is associated with the cable or with the method of wiring .
  It is probably true to say that one of the commonest methods of installing cables is still to push them into conduit and we shall devote most of out attention to this .