Lighting Circuits:Sequence of Control

Sequence of Control

The electricity supply to a domestic installation begins at the meter cabinet which houses the DSO service fuse, DSO meter and an isolator. This is the Main Supply Point.

The DSO supply cable is referred to as the service cable. The DSO service fuse and meter are sealed to prevent any interference with this part of the installation. The Nominal Voltage of the supply to domestic premises is 230 Volts. This is known as Low Voltage.

The control and distribution of the electricity supply to the installation is contained within one enclosure. It is referred to as a Distribution Board. This unit has its own main switch fuse, or a separate main switch and main fuse, or main MCB. This is followed by individual circuit fuses or more commonly nowadays, Miniature Circuit Breakers ( MCB’s ), to protect and isolate each circuit. There will also be neutral and earth terminals provided. See Figure 1.

Lighting Circuits-1024

Distribution Board

The distribution board may also house other protective or control devices such as Residual Current Devices ( RCD’s ), bell transformers, time-switches and contactors.

Figure 2 represents the sequence of control for a very basic distribution board. Depending on the installation requirements, a second or third RCD may be required and of course, more MCB’s, one for each circuit.

Lighting Circuits-1025

As can be seen, an RCD is not provided for the lighting and cooker circuits, although there are exceptions to this situation.

Incoming search terms:

Leave a comment

Your email address will not be published. Required fields are marked *