wiring systems and fault finding for installation electricians third 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 circuits.
The abundant 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.

1 Diagrams
BS EN 60617 symbols
BS EN 60617 gives the graphical symbols that should be used in all
electrical/electronic diagrams or drawings.

Since the symbols fall in
line with the International Electrotechnical Commission (IEC) document 617, it should be possible to interpret non-UK diagrams.

Figure 1 (continued)
Diagrams
The four most commonly used diagrams are the block diagram,
interconnection diagram, the circuit or schematic diagram and the
wiring or connection diagram.
Block diagrams
These diagrams indicate, by means of block symbols with suitable
notes, the general way in which a system functions.

Figure 2 (a) Security system. (b) Intake arrangement for
domestic installation

Wiring Systems and Fault Finding for Installation Electricians
6

Interconnection diagrams
In this case, items of equipment may be shown in block form but
with details of how the items are connected together

Figure 3 Two-way lighting system

Circuit or schematic diagrams
These diagrams show how a system works, and need pay no attention
to the actual geographical layout of components or parts of components
in that system.

For example, a pair of contacts which form part of,
say, a timer, may appear in a different and quite remote part of the
diagram than the timer operating coil that actuates them.

In this case
some form of cross reference scheme is needed, e.g. T for the timer
coil and T1, T2, T3 etc.

for the associated contacts.
It is usual for the sequence of events occurring in a system to be
shown on a circuit diagram from left to right or from top to bottom.
For example, in Figure 4, nothing can operate until the main switch
is closed, at which time the signal lamp comes on via the closed
contacts of the push-button.

When the push is operated the lamp
goes out and the bell is energized via the push-button’s top pair of
contacts