Advice wiring up a twin dimmer?

Question

Hi,
I am replacing a twin light switch with a twin dimmer, but I am puzzled by the way the switches were wired up.
Coming into the socket are two mains cables, labeled 1 and 2.
Both earths go to the earth in the housing.
Black 1 (live i gather) goes to the top of switch 1. Black 2 goes to the bottom of switch 2.
Red 1 goes to the bottom of switch 1, and then another red cable runs from that to the top of switch 2. The red from mains cable 2 is left hanging.

The dimer I have has 2 seperate units, with a live connector, a connector for the cable to the light, and an earth. I understand I just run a cable from the earth to the earth in the housing, but what do I do with the other cables? Why is that red cable left hanging in the air?
Chris

Answer 1

Disregard the 'hanging' red, it would appear to be un-used. Connect the red (supply/feed) with the red link to 'C' or L1 on each dimmer, then connect one black (switch wire) to L2 on dimmer module 1, and the second black to L2 on dimmer 2. If they are wrong way round to suit your lights(Left and Right) then swap the two blacks. Since the two blacks are considered live they should be marked with red or brown tape or sleeving. You appear to have a metal plate dimmer, so connect the earths together as well. If the markings on your new dimmer is different post them back here, different manufacturers use differing markings.

ADDED>> Ignore the references to white wiring and three way switches, they are US respondents who have very different terminology and systems. YOU have two one way switches, simple to connect as I have described.

Answer 2

Could be that the sparky who wired it up ran out of 3 core and earth cable and just used two twin core and earths so they would then have a spare on left over. I imagine that the switch is a two way type, ie that it is also swithed on and off via another switch in the room.

As long as you wire it up like the original it should then work ok, tape up the odd one after ensuring that the lights work as they should as it may have fallen out the switch when you took it off the wall. Always turn off the whole mains as people often bodge wiring and run lights off ring mains etc so be safe

Answer 3

I don't know what you guys are talking about! You cannot make two dimmers operate where two three way switches existed. One of the switches has to remain in the circuit.

I am going to be back as soon as I draw a diagram of what you are saying. Something doesn't seem right.

I'm back

Sorry. I cannot understand your problem. You must be talking about a dimmer I have never had the occasion to deal with. By "twin dimmer", you must mean two dimmers combined as one, which you install in the same box.(socket?) If that is the case, there is some internal connections between the two that only the wiring diagram that came with the dimmer would show. And you are not talking about 3 way dimmers.

So, I'll let some of the more learned answer your question.

Sorry I interrupted.

Answer 4

IF THE NEW SWITCH IS WIRED JUST THE WAY THE OLD ONE IS, THERE SHOULD BE NO PROBLEM. BOTH THE BLACK AND RED ARE LIVE WIRES AND THE WHITE ARE THE GROUNDS. THE EXTRA RED WIRE IS PROBABLY AN EXTRA WIRE. WIRE COMES IN 2/3/4 WIRE WIRE ALWAYS ADD A A EXTRA WIRE FOR THE GROUND FOR EXAMPLE 14-2 WIRE HAD THREE WIRES A BLACK, WHITE AND A GROUND. HOPE THIS HELPS, JUST KNOCK OFF THE POWER WHEN YOU REPLACE THE SWITCH