22 Wiring Systems and Fault Finding For Installation Electricians
Fault location Another major advantage of the use of PLCs for controlling systems is the relative ease of fault location. In the event of system failure, the keyboard and screen unit is plugged into the PLC and the condition of the system is displayed in ladder logic on the screen. Then, for example, any contact that is in the wrong position will show up.
DRAWING EXERCISES 1. Using BS EN 60617 architectural symbols, draw block diagrams of the following circuits: (a) A lighting circuit controlled by one switch, protected by a fuse, and comprising three tungsten filament lamp points, two double fluorescent luminaires, and one single fluorescent luminaire. (b) A lighting circuit controlled by two-way switches, protected by a fuse, and comprising three floodlights. (c) A lighting circuit controlled by two-way switches, and one intermediate switch, protected by a circuit breaker, and comprising three spotlights. One of the two-way switches is to be cord operated. (d) A ring final circuit protected by a circuit breaker, and comprising six double switched socket outlets and two single switched socket outlets. 2. Replace the symbols shown in Figure 1.18 with the correct BS EN 60617 symbols. Solutions are given at the end of the book.
