Help please with 2-gang 1-way dimmer switch install ...

[gifted amateur]

SUMMARY: I've just tried to replace a 2-gang 1-way regular switch with a 2-gang dimmer switch. I duplicated all the connections EXACTLY, but it won't work at all. I've replaced the old switch and the lighting works fine again.

So ... can anyone tell me what changes I need to make to the wiring?

Here's the current setup:

There are 2 separate ceiling lights in the room, which are switched individually on/off at only ONE place in the room (ie. 1-way) by a 2-gang regular switch (ie. a standard square switch box whose front contains 2 separate switches, one for each ceiling light).

Existing wiring (probably ever since the house was built in 1975) to the front part of the switches is ...

Top row of connections: L1 (unused), L2 (Red wire), Common (Black wire)

Bottom row of connections: L2 (Another bared red wire, which then continues on to the Common on the bottom row), L1 (unused).

Finally, a green earth wire connects to an earth point on the metal back box.

The new dimmer switch is an "Aurora", 400W/VA, "no de-rating required". There are 2 push/push rotary control switches on the front. Each of those rotaries has three connections points (C, L2 and L1) - and the two switches are (visibly) completely separate.

The instructions supplied with the dimmer switch give NO HELP AT ALL on how to wire such a 2-gang, 1-way setup!!

So I cabled it up copying the above existing connections exactly. But of course this means that two of my wires (a red and a black) go into one side/switch (L2 and C), but only one other wire (a red) goes into the other side/switch (into L2 and onwards into C). So the two separate sides of my 2-gang dimmer are not interlinked (correct??? - or not???) and I only have one wire going into one side (which surely means no circuit through it!!?).

Of course, I have left the earth wire untouched on the metal back box.


And I get no lighting at all, no matter what I do with the rotaries (push/push / rotate).

So: What do I need to do to get this up and running?

Final point ... I presently only have 2 x 60W bulbs in each 5-bulb light fitting (making 240W total), so I am well under the dimmer's max. rating of 400W/VA. But can someone separately advise me if that "400W/VA" rating means PER GANG or TOTAL? Each separate dimmer control connection block states 400W/VA as its max. load. So can I plan to drive 400W or 800W max. in the room???

Thanks in advance ...

 

[plugwash]

sounds like you are looking at your existing switch wrong, most likely the connections for each of the two switches are in a triangle not in rows.

 

[gifted amateur]

Aha, plugwash, that's the answer I needed! Thanks!

The division of the back part of the old double switch front cover into 2 triangles is not at all obvious, but when I looked carefully, there they were, moulded into the plastic. And then of course it all made sense, with each switch's triangle of connections corresponding properly with each of the 2 new dimmer's sub-units. Re-cabled, and it is all working nicely! Thanks again.

Finally ... can anyone answer my other question, repeated here:

Does the dimmer switch's "400W/VA" rating mean PER GANG or TOTAL? The packaging says 400W/VA, but each separate dimmer control connection block also has 400W/VA printed on it, as its stated max. load. So can I plan to drive 400W or 800W max. in the room??? I'd really appreciate a view on this ... it will dictate whether I have to use 5 x 40W max bulbs in each fitting (giving 400W total max load) or whether I can use 60W bulbs, allowing max. load of 600W when needed ...

 

[Lectrician]

400watt per dimmer.

If it was a grid assembly, and not a complete manufactured unit, then you would need to down rate them.

Always best never to run the units to full load, and never underload them either

All resistive loading i assume? No ELV transformers, or loads of mains voltage halogens? You would need to downrate the dimmer, and make sure the dimmer is capable if there was.

 

[Nijinski001]

Lectrician.

I know about de-rating for mains voltage halogens just because I know. I sthere a table somewhere that gives de-rate values for MV Halogens, Selv Pelv etc?
I can't find one in the OSG.

 

[gifted amateur]

Thanks, Lectrician. And there are no transformers or halogens involved ... just regular 60W SES bulbs in living room ceiling fittings. And no plan to load above 300W per dimmer module.

Fully reassured now! Cheers ...