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18th edition iet wiring regulations wiring systems 7th edition pdf

The aim of this book is to help the reader to approach the drawing and
interpretation of electrical diagrams with confidence, to understand the
principles of testing and to apply this knowledge to fault finding in electrical

The abundant colour diagrams with associated comments and explanations
lead from the basic symbols and simple circuit and wiring diagrams, through
more complex circuitry, to specific types of wiring systems and, finally, to the
methodical approach to fault finding. The new edition has been brought fully in line with the 18th Edition IET Wiring Regulations.

Important terms/topics covered in this chapter:
BS EN 60617 symbols
Circuit convention
Relay logic

By the end of this chapter the reader should:
be aware of the correct symbols to be used on diagrams,
know the different types of diagrams in general use and why they are
understand circuit convention and its importance in interpreting
understand simple relay logic and its application to PLCs.


This is an area often overlooked or even ignored. The IET Wiring Regulations
require that ‘diagrams, charts, tables or equivalent forms of information are
made available’ to the installer and inspector and tester.