DIY Doctor

Main navigation

Do I need an earth for new dimmer switch with metal front?

Postby damien_cleveland » Thu Jul 08, 2021 11:33 am

Hi all, thanks for taking the time to look. My old dimmer switch finally gave up and I am attempting to fit a replacement. The new one is still plastic but the dimmer switch its self has a metal front (inside not outside the faceplate). Do I need to try and connect back to the earth in the metal back box?
Dimmer.PNG (122.78 KiB) Viewed 98 times

front dimmer.PNG
front dimmer.PNG (32.53 KiB) Viewed 98 times

I have run and rerun run the wires (just two reds). I have connected them to the labelled C and L1 but no response from the lights.

(Full disclosure, never touched lights before, so I connected the earth to C ... as I had it spare... that was dumb, it sparked when I tried to turn the fuse box back on. Did I cook the dimmer switch maybe? I have since done some reading and learnt C does NOT equal grounding point)
back dimmer.PNG
back dimmer.PNG (109.74 KiB) Viewed 98 times

Any help is appreciated, I figured out what l1 l2 and C mean finally, but I think I have cooked the switch..... unless I need to earth it somehow.

**sorry its my first post here so hopefully I got everything right and didn't break some rules.
Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Thu Jul 08, 2021 11:08 am


Simply Build It

Postby Mr White » Thu Jul 08, 2021 6:33 pm

First thing, you do need a new dimmer switch, you have permanently damaged the previous one.
You should always earth anything with exposed metal unless it is double insulated which is denoted by a symbol which is a square within a square.
The dimmer switch you have does NOT have any exposed metal, so does not require an earth.
You are also correct that your new, new dimmer switch, the wires should be connected to C and L1

I assume your lamps are halogen? if they are not halogen then that dimmer switch is not compatible (I can not quite make out what it says) But if they are halogen no worries.
Mr White
Rank: Site Agent
Progress to next rank:
Posts: 949
Joined: Tue Jun 20, 2017 9:54 pm

Postby ericmark » Thu Jul 08, 2021 9:28 pm

The instructions are here ... ctions.pdf the main point is it is not suitable for LED lights, so seems a little pointless fitting it.

But the diagrams are good, can't see how you got it wrong, assume no instructions in the box.
Rank: Project Manager
Posts: 2567
Joined: Fri Oct 02, 2009 8:49 pm
Location: Llanfair Caereinion, Mid Wales.

Postby damien_cleveland » Sat Jul 10, 2021 6:10 am

Thanks both, I think I may wait for my father to come round and demo this... he is an electrical engineer. Guess I should have paid more attention when he was talking.

Ill chuck this one in the bin and get a new one.
Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Thu Jul 08, 2021 11:08 am

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics