Types of Electrical Diagrams

There are four basic types of electrical diagrams:

• schematic
• wiring
• block
• pictorial

Schematic diagrams

The schematic diagram (Figure 2), often called a ladder diagram, is intended to be the simplest form of an electrical circuit. This diagram shows the circuit components on horizontal lines without regard to their physical location. It is used for troubleshooting because it is easy to understand the operation of the circuit. The loads are located on the far right of the diagram and the controls for each load are located to the left. To understand the sequence of operation the drawing is read from the upper left corner and then from left to right and from top to bottom.

Wiring diagrams

The wiring diagram (Figure 3) shows relative layout of the circuit components using the appropriate symbols and the wire connections. Although a wiring diagram is the easiest to use for wiring an installation, it is sometimes difficult to understand circuit operation and is not as applicable for troubleshooting.

Block diagrams

The block diagram (Figure 4), also called a functional block diagram, is used to describe the sequence of circuit operation. This diagram indicates by functional descriptions, showing which components must operate first in order to get a final outcome. They do not refer to specifics like device symbols or related wire connections.

Pictorial Diagrams

A pictorial diagram shows the circuit components in more detail, as they really look, and indicates how the wiring is attached. These diagrams can be used to locate components in a complex system.

Interpreting Wiring Diagrams

The ability to read and understand a wiring diagram is important for any tradesperson. You may need to repair a power tool, install a heat pump, or try to find a fuse in a car. Any of these situations requires an ability to read and understand a wiring diagram.

Electrical symbols may be different for each manufacturer, but in most cases they are standard. Every manufacturer’s diagram should have a symbol identification chart or “key” located in the wiring book. Some examples of electrical symbols are shown below.