Replacing 2-gang dimmer, different smbology

[exburyman]

I have just bought a 2-gang 2-way dimmer to replace an existing similar switch. I followed the logical process of noting down the connections to the old dimmer before removing it in order to map them to the terminals on the new dimmer. Unfortunately the symbology is different on the new dimmer. The old one uses L1, L2 & C, whereas the new one uses L, Sw & a sinewave with an arrow through it. I understand from the instructions that the L represents the live feed and the sinewave represents the load side. I would like help in confirming my understanding of how to connect the replacement switch.

The switch is to control 2 light circuits, 1 having 2 ELV halogens and 1 a standard HV light. On removing the old front plate I found 2 cables entering the back plate (I presume one is for each circuit). Each is a twin & earth cable, i.e. black, red and earth. The first cable has its red core connected to the L1 terminal of gang 1 which is connected via a link wire to L1 on gang 2. The black core is connected to the C terminal on gang 2. The second cable has its red core connected to the C terminal on gang 1 and the black core is terminated by a terminal block, i.e. not connected to anything. Both earths are obviously connected to the backplate earth.

My question is simply, do I replicate this by mapping the old and new terminals as follows:

old L1 to new L
old C to new sinewave with arrow
old L2 to new Sw (i.e. both left unconnected)

Secondly I would like confirmation that the original wiring is the correct way around as I have read on this forum posts about the 'standard' way to connect the live earth and load side.

Many thanks and sorry for the long-winded description.

 

[mapj1]

It sounds as if one of the lights really is two way control, and the other 'borrows' the red (live) for the top of a two way strapper circuit.
Ideally you need to know the colours used at the other end of the two way switch too (i.e. the one that is not the dimmer, but just on/off)....
there are a number of ways of doing this, it helps to know whih you have
the L1/2 + comm markings are almost universal on 2 way switches. The common is the slider and connects either to terminal "lamp one" or "lamp two".
You need to reconcile the makers instructions on the new switch with this description - I'd expect as described, with the slider replaced by the dimming electronics.
If used for single pole switching (no second switch) the common slider and one or other of the L connections is used, depending if you want 'on' to be up or down for the switch. On a push switch, with no sense of up or down, the L1/L2 distinction is arbitrary. The unused terminal is then left disconnected.
Best to draw out whet you have, and if its not clear to you how it works, try and scan it or photograph it and post it.


The situation is perhaps appears slightly confused in that the live comes in on one core, and is used for both lights, and two switched lives go back, one as the second half of the cable that supplied the live, and the other as the used part of a half unused pair. really you only have three business wires, one live in, and two switched lives out (one black, one red...)

From your description what you propose to do will do no harm, but you may find that the behaviour of the two way part is not quite as expected, in which case a swap of common and one of the other 2 is called for.
hope this helps.
M.

 

[breezer]

is the new dimmer capable of hadling the load? (i also assume the previous one was a dimmer, you did say similar, but not the same though)

 

[exburyman]

Mapj1, thank you very much for your advice. I can confirm that neither circuit is 2 way. If it will help I will look to take a photo of the current configuration and post it here.

Thanks again.

 

[exburyman]

Breezer, thank you also for your comments. The new dimmer is digital and has a 2 x 250W rating. The 2 light fittings one of the gangs is to control each have 5 10W G4 halogens making 100W load in total so I think the dimmer should cope. The other is for a standard 60W bulb.

The old switch is also a 2-gang dimmer but not digital.