Dimmer replacement woes

[MikeBpl]

You know when you think... this can't be difficult, it'll only take a couple of minutes... the n it doesn't?

I've read through other posts but it has only left me more confused by the number of variations to the theme.

My plastic dimmer switch broke. I decide to replace it with a metal faced one.

I took off the plastic one. It had 3 wires. Two red wires were both in the terminal marked L1 and a black wire connected to the terminal marked 'c'

The new dimmer switch (Varilight touch control master) doesn't have any terminals marked L1 or C.

Where the devil do the wires go?

 

[jj4091]

What terminals does it have?

 

[securespark]

And does it require an earth connection?

 

[baldersj]

The 'C' connection will probably be replaced with a wiggly line with an arrow through it. Be interested to see what the other connections are marked as.
As Securespark says, a metal switch plate will need an earth connected to it. Were there any earths connected to the backbox when you took the plastic switch off? Is the backbox plastic or metal?

 

[MikeBpl]

The backbox is metal, but there is no earth point as I notice there are on newer metal back boxes.

There was no earth wire connected to the old box but as it was plastic i suppose it didnt need it.

The symbols on the new switch are marked as the squiggly line with the arrow through it that you mentioned earlier, one witha capital letter 'S' and one that says "Live" It also says "must be earthed"

 

[baldersj]

But are there earth cables? If the cables are Twin & earth, the bare earth wire may have been snipped back. Or is it just missing?

 

[MikeBpl]

no sign of any cables other than the 2 red ones and one black one

 

[baldersj]

This is quite common in a lot of older wiring systems. Also some DIYers cut back the earth conductor in Twin & Earth cable when fitting plastic switches, which is why I asked.
Metal switchplates (and ideally the whole circuit) really need an earth. If you feel confident, you could check at the Consumer Unit whether the lighting circuit has an earth. If not i'd get an electrician in to advise you. Either way, if you can't connect to earth somehow, I'd strongly recommend that you get a plastic switch for now.

 

[MikeBpl]

yes, sadly i was coming to the conclusion that i need to revert to a plastic switch until i can get an electrician round. sigh, thought it would be such a simple, cheap job

 

[Paper Spark]

The backbox is metal, but there is no earth point as I notice there are on newer metal back boxes.

There was no earth wire connected to the old box but as it was plastic i suppose it didnt need it.

Even if a plastic switch is used the back box should still be earthed as it's possible the plate fixing screws could become live if the switch feed came adrift and touched the box.

 

[MikeBpl]

Well I went back and bought a plastric switch and wired it with the black wire in the C connection (WEll, there isnt a C connection but theres a wiggly line with an arrow through it) and the two red wires to the connection marked "live".

It doesnt work.

sigh

 

[FootSore]

no sign of any cables other than the 2 red ones and one black one

Is the light usable from two switches or just the one dimmable switch? If two switches then you will need a 2 way switch. These are often marked L1 & L2 with C on older switches.

FootSore

 

[baldersj]

Hello again Mike,

Nothing is ever as easy as it looks!
Can you post any pics of the cables you have or the new switch?

Just out of curiosity, why were you changing the switch in the first place?
P.S. If the old dimmer switch worked, then replacing it with another dimmer is fine, you don't HAVE to use 2way switch!

 

[securespark]

Even if a plastic switch is used the back box should still be earthed

Unless you use nylon screws as a temporary measure, then there would be no exposed metalwork to touch.

 

[FootSore]

My plastic dimmer switch broke. I decide to replace it with a metal faced one.

He's replacing the switch becasue it broke

P.S. If the old dimmer switch worked, then replacing it with another dimmer is fine, you don't HAVE to use 2way switch!

Unless the old dimmer switch was a 2-way dimmer switch in which case it would need to be replaced with another 2-way dimmer switch. On the assumption that it was wired as 2-way switching.

I am trying to ascertain why he would have three cables at the switch.

Reasons I can think of include the horrendous thought that someone only had that cable but used one as earth and didn't make any attempt to label anything.

Or it is a 2-way circuit with another switch not mentioned ( I know he stated that they were both wired to L1 but it seemed an easy thing to rule out)

Two reds were used to run to a separate lights with the neutrals commoned elsewhere.

Someone wanted a live for something and this was a handy place to get one.


Next questions are what lights are you trying to dim are they normal incandescent lights, LV Halogens, HV Halogens, Energy Saving etc. Not all dimmers are suitable for LV lighting. I haven't used a Varilight touch control master before (most of my house uses Futronix lighting controllers & has a mix of LV Halogen, LED, and few Incandescent) so not sure if they are LV compatible.

FootSore