2 live red wires - replace with new dimmer?

[JayUK20]

I bought a dimmer light switch with metal faceplate and went to swap it out for the old rocker switch but noticed the installed rocker has two red wires and no earth so I cannot use the new dimmer so I'll swap it for a plastic one.

On the old switch I cannot see anything to indicate COM or L1. Does it matter which red goes in COM/L1.

 

[Dextraneous]

Have you actually tried to connect it?

 

[flameport]

Does it matter which red goes in COM/L1.

No, either way is fine.

 

[Taylortwocities]

Sometimes the earth wire is cut right back. Have a good look to see if it is just there, but not sticking out of the outside sheath of the cable.

Are these two separate wires with no external sheath? Post a picture if you not sure.

 

[ericmark]

Be aware although you may find an earth it may not be connected. Before 1960 often lights were not earthed but any repairs will have been done with new cable which will have an earth wire.

I remember in one house on the Falklands trying to connect up all the earth wires they were all there but not connected. It transpired there was some junction box in the ceiling space and there was no access so I was unable to connect them all. I advised the owner "Falkland Island Company" but I never found out if completed or not. A tad to far to wander over and check.

But the point is any house wired before 1970 really needs to have earth checked to see if really an earth simply connecting a wire is not good enough.

 

[PrenticeBoyofDerry]

I echo the above comments on a standard one way rocker switch it will not matter which terminals you use for the perm/com live and the switch live/L1.

The switch may appear to be upside down, it will just require spinning around.

If a metal switch plate is desired, double check the sheaths of either cable if singles or the one sheath if a twin. They have in the past been cut back and they can be extended via connector in the backbox. As previous post even if an earth core is present it will require to be confirmed that is actually connected to earth, there is a good chance if one earth core has been cut back others will have also, so you would have to remedy them all, to get continuity.

Note: If you do fit a dimmer for rocker, follow the manufacturers instruction on lamp types that can be controlled and the way the com and L1 should be connected.

 

[Taylortwocities]

The wiring could also be enclosed in metal conduit, that "could" provide the earth connection. That's why i requested pictures!

 

[PrenticeBoyofDerry]

The wiring could also be enclosed in metal conduit, that "could" provide the earth connection. That's why i requested pictures!

Very True, but again continuity would still be required to be proved.

 

[JayUK20]

Thanks for the replies.

I've attached a picture but I'll probably go with advice from. The above.

Untitled

• JayUK20
• 15 Mar 2015
• 1

 

[deadshort]

Thanks for the replies.

I've attached a picture but I'll probably go with advice from. The above.

Untitled

• JayUK20
• 15 Mar 2015
• 1

The green sleeved wires are your earth, connect an earth to these and then your switch earth terminal.

Regards,

DS

 

[PrenticeBoyofDerry]

Untitled

• JayUK20
• 15 Mar 2015
• 1

The picture shows two green sleeved conductors that are terminated to the backbox, so the cores are there, they now need to be proved that they are earthed. So continuity tests are required.

If you have one solid/rigid lug on the backbox, then the switch plate does not require earthing, but belt/braces I would.

But looking at the backbox, I do not believe your dimmer will fit to it, as the backbox is too shallow and requires replacing with either a 20mm or even a 35mm.

 

[sparkwright]

That's the earth all right.

We often advise you to check that the earth wires are in fact connected to earth, though not something a DIYer can necessarily do successfully.

Spacers are available to go between the switch faceplate and the wall, to save you sinking in a deeper box. These are usually plastic, so a plastic switch may be best.

The spacers make the switch look a bit naff, but will do until you redecorate.

 

[JayUK20]

Ok I popped the new plastic dimmer on and it fits but it's fairly snug.