Replace one switch with a dimmer in 2 way lighting circuit

[justin99]

Dear all,

I have checked the references, and cannot explicitally see the answer to my question so am posting.

The light in question is a landing light 5 x40W bulbs in total, with a switch upstairs and downstairs. Nothing unusual here!

Pending newborn, I want to replace the upstairs switch with a dimmer. Have bought a 400W 2 way dimmer and presume I replace the Com, L1 and L2 like for like. L1 and L2 currently have 2 wires in each.

Is it as simple as this? The circuit diagrams that came with the dimmer were a bit confusing. Also, I can't seem to screw the dimmer switch back onto the wall plate - even using the old screws? Is this a common problem with different switches - guess i should get some longer screws?

Also, there are several other wires (untaped) behind the switch. Should these be insulated, or is this normal practice?

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[ricicle]

Yes it is common for L1 and L2 to have 2 wires in each and 1 in C. (2 core +earth switch cable from light and 3 core+earth from switch to switch)

Longer screws are available from wholesalers or DIY stores (Don't get conned into buying a whole pack!)

If the spare cores in the back of the switch are unused I would isolate the power and at put them into the earth terminal in the back of the box.If this is impractical I would at least put some tape around the ends

 

[securespark]

When you say you have a problem with the mounting screws, is it because the switch is too deep for the box?

In which case you need a shallower switch or a deeper box...

 

[justin99]

some longer screws will do the trick!

 

[Taylortwocities]

Longer screws may not do the trick. If the dimmer is too deep for the box then the wires will get trapped when you tighten up the screws.

With long screws make sure you do not trap the wires in the box, if you do it makes the house go all dark

TTC