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badgerbrian1974 02-17-2008 01:22 PM

Changing A Dimmer

So im trying for the first time to change out a light switch with a dimmer.
The dimmer is a Lutron Skylark S-600P-WH.
This has 3 wires - 2 blacks and one green ground.

So i turn of power at the junction box and take of switch casing.
This switch is only a year old its a standard on /off switch.
The switch has two black wires going to it.
Inside the gang box -I see the following -

The box has wires coming from above and below -

One black comes from the gangbox hole at the bottom, and into a cap.
The cap also contains the bottom black wire from the switch and one black wire coming from top hole to the left of the gangbox.

The 2nd black wire from the lightswitch (the one at the top of the switch) is going straight off and up the top of the gangbox via the right hole.

There is a White wire (neutral?) that comes form the bottom hole and into a Cap.
Then from the top left and right holes come 2 other white cables which are joined in the cap.

Finnally on the left top hole there is a red wire that comes out and just stops inside the box.(not connected to anything from what i can see)

So my question is - obviously i can tie in both black cables from the dimmer into the caps with the black cables currently attached to the switch.
but what do i do with the green cable from the dimmer?

Thanks for your help

jwhite 02-17-2008 01:56 PM

Connect the greeen wire from the dimmer under the same wire nut (cap) with the bare wire from the other cables.

badgerbrian1974 02-17-2008 02:34 PM

The white cables?

220/221 02-17-2008 03:22 PM

Green goes to BARE.

Green = ground = safety

If you have no bare or green wires in your box, some would suggest that you cut the gren wire off.....but then others would chime in and make a big fuss over how someone could somehow get killed by coming in hard contact with the coverplate screws while there was a fault in the dimmer.

badgerbrian1974 02-17-2008 03:43 PM

yeah i thought ground was saftey - just found it strage that this was put in just a year ago - and unless im missing something i dont see a ground screw in the box- and neither is theere a green ground wire or any bare copper wire - could i just screw a screw into the frame of the metalic box and ground it off to that?


badgerbrian1974 02-17-2008 06:12 PM

So there is nothing i can do - if there is no ground in the box?
can i just leave the green wire on there coiled inside teh box - would rather not cut it off

Stubbie 02-17-2008 07:43 PM


The electrical code provides for using your dimmer when it is for replacement purposes only. If you have no grounding means in the wiring just cap the green wire or you can connect it to the box. It basically serves no purpose in your case. You must use a non-conductive cover plate not any that are metal.

If however someone has cut the ground wires then you will have to replace the wiring or get access to the cut ground wire. It sounds like your wiring does not contain an equipment ground . The only other thing would be if you have metal conduit instead of romex style cables. You can test for ground by simply touching a incoming hot wire with one probe and the other to the metal box.

badgerbrian1974 02-17-2008 08:30 PM

All the electrical cable incoming before it reaches the actual box and is stripped is BX as far as i know.
Ok so il just cap the green.
All the coverplates in the house are plastic.

thankyou for your help

Stubbie 02-17-2008 09:15 PM

If your cable is BX and I mean the real McCoy and not AC cable then it technically cannot be used as ground but what I would do is connect the green wire to the metal box rather than cap it. A simple grounding clip like this will do with short piece of copper solid wire wirenutted to the green stranded and the solid under the clip. Your BX may not be the best ground but it is better than nothing...:)

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