HOW TO WIRE AN INTERMIDIATE SWITCH

How to wire a intermediate switch?

How do you wire a intermediate switch iv got 3 door ways 2 enter a room, all with I switch at each door way all to operate the same light. 

BEST ANSWER

First and foremost make sure that you have pre-notified your local authority building control department and paid their fee so that you can undertake DIY electrical work in your home - failure to notify and get consent for part P electrical work can put you at risk 

ii) that the electricity supply is isolated so that the lighting circuit is dead and safe to work on.

Intermediate switch is really just an extension of two way switching, but does require a 4 terminal intermediate switch as well as 2 two-way light switches. A two way switch can be identified by looking at the terminals on the back of the switch . There will be a Com (common) terminal a L1 terminal and a L2 terminal. On an intermediate it will normally have L1, L2, L3 and L4.

Three core and earth cable is required to install two or three way switching and this should be run from the first light switch to second switch (intermediate) and then to the third switch. Switch one is the switch that contains the live wire and switched live wire (i.e. the pair of cables that were originally there for the old single way switch)

The existing live (could be red or brown) should be connected to L1 with the red or brown of the three core cable, the switchline (blue or black) should be connected to L2 with the blue or black of the three core cable, and the common terminal should have the single yellow or grey wire in it.

At the mid point you fit the four terminal intermediate switch, with The two wires from the first light switch, which are Red and Blue go into the L1 and L2 terminals. (new colours will be Brown and Black)

The two wires that are going to the final switch, which again will be red and Blue go into the terminals marked L3 and L4. (new colours will be Brown and Black)

The yellow wire (new colour Grey) is simply joined together using a terminal block, this can be taped up with insulation tape and left in the back box.

The third switch is similar to the first with yellow (grey) as the common and red and blue or brown and black as L1 and L2.

You also need to remember that when installing cables they need to be at least 50mm deep in the wall or protected by an RCD (yes even the lighting) this is to comply with BS7671:2008 requirments.

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