Replacement Dimmer Switch - wiring question

[kefter]

Hi

I am changing an old gold dimmer switch for a more modern brushed steel dimmer switch but am confused with the wiring i've found. Both dimmers are push on/off and twist to dim. There is only 1 single dimmer switch controlling the light. Can you help?

I found the following (pics attached): -

red connected to L1
black connected to C
yellow / green (earth?) connected to L2

As this is a replacement only the instructions tell me to wire the same way as found except earth as per instructions. The earth connection to L2 is confusing me

Can anyone advise?

thanks

 

[Iggifer]

Do you have any means of testing? That looks VERY wrong to me

 

[kefter]

Iggifer - thanks for quick response......
I don't have any way of testing. What would I need and what would I be testing for?
thanks

 

[Iggifer]

Ok, first things first, is there another switch that controls this light?

 

[kefter]

Nothing else controls this light

 

[Iggifer]

Ok, well that's somewhat less concerning then.

But really, you want a multimeter to verify that, that earth is actually an earth. It's likely just a case some moron has put it in the wrong terminal.

If you can get your hands on a multimeter set to continuity (Ω), with the power off, test between that earth at the switch and that at the light fitting - you will very likely need to use something conductive to extend the reach. If you have a spare bit of flex you can use that with the help of an assistant.

I would be very wary doing anything until the wiring has been verified.

 

[endecotp]

The person who fitted that was a dangerous idiot. You should probably assume that they have done other equally dangerous things elsewhere in your house. Get the whole place checked by a competent electrician ASAP.

 

[chivers67]

Can you have a look at the light fitting and take as photo too?

 

[Iggifer]

Can you have a look at the light fitting and take as photo too?

I thought that, but I wouldn't be happy advising it was ok to connect up based on a photo of the rose, given how wrong the switch was and there's no guarantee there's no JB. Chances are if the rose is ok, the earth is ok, but I wouldn't want to risk it

 

[kefter]

Thanks for all the replies - I'll get a multimeter and check it out. If i'm still not happy then I'll get an electrician in
thanks

 

[kai]

It looks like a wiring mistake, the earth must go into the Earth terminal, not the L1 or L2 terminals.
At present you do not appear to have an earth to your dimmer, unless the back box is earthed steel.
Have you checked that the dimmer is compatible with your light fittings lamps?
It may fail with a bang if there is a mismatch between lamp and dimmer.

 

[Iggifer]

It may fail with a bang if there is a mismatch between lamp and dimmer.

Have you ever seen this happen?

 

[stillp]

It may fail with a bang if there is a mismatch between lamp and dimmer.

Have you ever seen this happen?

I bought some LED GU10 lamps that were claimed to be dimmable, turned on the dimmer and the MCB tripped. Surprisingly, neither the LED lamps, nor the dimmer (Clipsal), were damaged.

 

[kai]

Luckily it was an MCB installation, that tripped fast enough to save the dimmer circuitry. If you had a Rewireable fuse instead, the dimmer circuitry may have been wrecked by the sudden current surge.

 

[kefter]

Kai
There is only 1 earth wire (mistakenly(?) connected to L2). There is nothing connected to the existing switch earth terminal (picture 1 top right) and I cannot see anything else connected to the box which appears to be plastic not metal so guess you're right, currently not earthed.

Regarding mismatch comment..... I am replacing an existing gold dimmer switch with a new silver one and the light currently works and dims ok (notwithstanding the wiring anomaly!) so assuming this will be ok

Have also checked a couple of other single dimmers in the house and both have red to C, black to L1 and Earth connected to E and again no earth connected to back box which again appear to be plastic.

Hopefully just a one-off mistake....

Thanks