Wiring Diagrams For Lighting Circuits – Junction Box Method

Wiring diagram of a one way lighting circuit using junction boxes (fig 1).

One way lighting circuit using junction boxes fig 1

The junction box should be wired as shown below.

Lighting junction box fig 2

Explanation of above picture. (fig 2)
The feed cable comes from a previous junction box or from the consumer unit, the red, black and earth wires are connected to separate terminals. The earth wire must be covered with green/yellow sleeving.

The cable going to the light switch is connected as follows (fig 2). The red wire going to the light switch is connected to the same terminal as the red wire from the feed cable, the black wire from the light switch is connected to the spare terminal (terminal not yet used), and the earth wire is connected to the same terminal as the earth wire from the feed cable.
The black wire from the light switch, should be marked with red sleeving to show it is a live wire, but in practice is often left unmarked if you come across this it is good practice to sleeve the switch wire.

The cable going to the ceiling rose is connected as follows (fig 2). The red wire going to the ceiling rose is connected to the same terminal as the black wire (marked with red sleeving) coming from the light switch, the black wire going to the ceiling rose is connected to the same terminal as the black wire from the feed cable and the earth wire is connected to the same terminal as the earth wire from the feed cable.

The following picture is exactly the same as the picture above with the addition of another cable which provides the feed for the next junction box.

Lighting junction box fig 3

The cable going to the next junction box is connected as follows (fig 3). The red wire going to the next junction box is connected to the same terminal as the red wire from the feed cable, the black wire going to the next junction box is connected to the same terminal as the black wire from the feed cable and the earth wire going to the next junction box is connected to the same terminal as the earth wire from the feed cable.

A one way light switch is quite easy to wire up.

One way light switch fig 4

The cable going to the light switch is connected as follows (fig 4). The red wire is connected to L1 or in this case the top terminal, the black wire is connected to the common or in this case the bottom terminal and the earth wire is connected to the earth terminal. If you are using a plastic switch the earth wire will need to be connected to the terminal in the terminal box (as shown above) because there are no earth terminals on plastic switches.

A two way light switch can also be used in in place of a one way light switch, in this instance the red wire is connected to the common (C) terminal and the black wire is connected to the (L1) terminal. The (L2) terminal is unused.

A metal light switch must be earthed as seen below.

Metal light switchfig 5

Safety AdviceIf you are using metal light switches (fig 5) make sure you connect the earth wire to the earth terminal on the switch and fit an earth link wire from the switch to the earth terminal in the back box.

When using a ceiling rose on a circuit that utilises junction boxes, again the wiring is quite easy, the difficult part is working at height and above your head.

Ceiling rose fig 6

The cable going to the ceiling rose is connected as follows (fig 6). The red wire is connected to the same terminal block that contains the brown wire going to the lampholder, the black wire is connected to the same terminal block that contains the blue wire going to the lampholder and the earth wire is connected to the earth terminal.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s