2 GANG SWITCH REPLACEMENT

[shinysheff]

Hi, I'm replacing a 2 gang switch which has a brass faceplate with a similar chrome type faceplate. The two switches operate 7 separate wall lights in the lounge - three off one switch and four off the other. The current wiring is as follows: 3 core cable with red connected to L1 on gang1, earth connected to earth terminal on wall back box and black/ brown not connected to anything. The are then two red cables from the light circuits with one connected to common on gang1 and the other connected to L1 on gang2. Finally a grey sleeved cable connects common on gang1 to common on gang2. I was planning to just reconnect in exactly the same way but have two questions. The new faceplate has an earth terminal and instructions say that there should be an earth connection between this and the earth terminal in the back box. Presumably I just run a short piece of wire between the two. Secondly, why is the black/brown on the 3 core unused and does it matter. The old faceplate has been on for over 15 years. thanks, hope this makes sense

 

[bernardgreen]

Connect the same way.

Explanation

Red wire to the commons is the live feed to the two switchs from the consumer unit ( probably via the ceiling rose )

The wires from the L1 terminals are switched live to the lamps.

The unused wire is a spare and should be in a single terminal block to insulate it.

My preference with metal faced switches is to take the earth wires ( sleeved in yellow/green sleeve ) to the earth terminal on the switch with a lead from there to the back box. This becasue I do not trust the screw on the back box to remain tight and the face MUST be earthed.

 

[shinysheff]

hi bernard, thanks for the advice.

 

[shinysheff]

Supplementary: Chrome faceplate now fitted and wortking as per advice. Now replacing a second brass faceplate with new. The old faceplate when opened up was not earthed. There is the end (1/4") of a bare wire visible from the 3 core that I assume is the earth. Can I just make a connection via a terminal block to feed some more earth wire to the faceplate? There also doesnt appear to be an earth terminal connection on the back box - is this essential? Again this faceplate has been on for 15+ years - what has been the risk during that time?

 

[Cremeegg]

Never assume anything - what appears to be an earth may be live! Use a meter to test if the assumed earth is not live then test for continuity between it and a known earth.

If it is as you assume then yes extend the wire and earth the faceplate. Just because bad practice hasnt lead to any problems in 15 years doesnt mean you'll get away with it in the future.

 

[securespark]

The unused wire is a spare and should be in a single terminal block to insulate it.

NIC advice is to ground any unused cable cores.