Dimmer Switch

[ceresdelta]

Hi,
I'm trying to replace a double dimmer switch that controls 2 sets of lights. 1 dimmer controls ceiling lights, and the other controls 2 x Alcove lights.

When I took the old switch off the wall I found 3 red wires coming from 2 different sides of the box connected to the switch and 1 link as per my diagram below. The old switch has no labels to indicate wiring other than "Connect wires either way round".

My new switch is on the right, can anyone tell me how to connect my new switch?

Many thanks

EDIT: Sorry, the new switch has the wavy line with an arrow through on the middle terminals not COM

 

[flameport]

The same using Com and L1. L2 is not used.

 

[ceresdelta]

Thanks, which should I put the link in?

Com-com or L1-L1?

 

[securespark]

The wavy line with an arrow through it is usually the output.

What do the instructions say?

If you have no instructions, it might be wise to look them up on line.

 

[ericmark]

The wavy line with arrow normally means com plus regulation, however not always, some dimming switches are designed to talk to each other and the wavy line with arrow means communication link not common terminal. So there is only one option. Read the instructions which came with the switch.

 

[ceresdelta]

Thanks for the help, nothing I did could get it to work. I even tried putting a regular 2-gang switch but no luck. Turns out I can't even detect the permanent live with my tester so I might have bigger problems so a call to an electrician is in order.

This started from a powercut which I assumed broke the dimmer, how likely is it that it damaged something else in the room? The rest of the downstairs lights are fine.

 

[securespark]

What is your tester?

 

[ceresdelta]

This is the tester I have: http://www.diy.com/departments/bq-pen-type-voltage-tester/179657_BQ.prd

It seems to work when I test other light switches, but I'm getting nothing from the one in question.

 

[securespark]

You really need a two-pole tester.

That is not to say your pen tester may be correct, but you need to be able to test voltages between
L, N and E and continuity would be helpful as well.

Have you changed other switches or light fittings?

If so, you may have made a mistake and ended up with a break in the wiring.

Have any circuit breakers popped off?

The other possibility is that the lighting in that room is via a spur off a non-lighting circuit, in which case the fuse in the spur could have ruptured.

 

[ceresdelta]

I have a digital multimeter, what should I be looking for in terms of voltage / continuity between the wires?

I did change a light switch on the wall behind the problem one. So I think a wire breakage is a very real possibility.

 

[securespark]

Well, you are looking (carefully) for mains voltage at the switch.

Turn off the supply, check for dead, then remove the switch and put terminal blocks on the wires.

Make sure the MM leads are set up for voltage and you have the correct voltage setting on the dial.
On reapplying power, you are looking for mains voltage across one of the reds and earth.

If you find nothing, it is worth going back to the switch on the other side of the wall (with the power isolated again) and checking your connections there.

You would only really need continuity if you had disturbed some ceiling wiring and needed to check which was the switch drop.

 

[securespark]

Looking again at the diagram as you have drawn it, the live comes into the switch as part of a twin and earth cable. These often (but not always) connect up in the ceiling space, not at switches, whereas if the live feed to your dimmer switch is connected in an adjacent switch box, it is often (but not always) done with single conductor cable.

So to double check:

You haven't altered any ceiling wiring?

You have only altered one other thing on the circuit, which is the switch on the other side of the wall to the dimmer in question?

You have checked the CU for tripped/ blown devices and there are none?

 

[ceresdelta]

Got it! Turns out the switch on the wall behind had a wire feeding the live from the switch to my problem room. When I replaced it I had wrongly assumed the feed had fallen out of a connector block in there - in reality it had fallen out of the old switch.

All sorted now. Time for a brew! Thanks for the help/advice securespark!

 

[securespark]

Excellent!