Option for running ground to a light switch.....

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  #1  
Old 01-20-13, 03:36 AM
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Option for running ground to a light switch.....

Background:

Old house (1953) in Santa Clara Country California

House wired with 2 wire NM _NO_ grounding.

Had grounding setup for all sockets with new stand alone grounding wire run under house. I believe this goes from the grounding rod to the panel, then from the panel to each socket. Only sockets were grounded, not switches.

Now I have new dimmer that requires ground which is on a wall with a grounded socket about 4ft away.

Idea:

Want to run 12AWG solid 3 wire behind baseboard, and using only ground wire in new cable, connect up to the ground in the socket to give the new dimmer switch proper ground.

Have a drawing here of what I want to do https://twitter.com/the_solutioneer/...291712/photo/1

Question(s):

Is this A: Safe B: Functional C: Stupid (multiple choice)

Or said another way, can you daisy chain ground from any known good ground wire?

Or do all ground wires need to run directly back to panel?

Or can you only share ground between items on the same circuit?

Thanks for any/all help!
Jon
 
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  #2  
Old 01-20-13, 04:48 AM
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Welcome to the forums! I think what you will find is that your dimmer requires a "neutral", not a ground. If your present switch only has a switch loop in it, coming from a powered light fixture, you do not have a neutral in the box. Tell us all the wires in the switch box. Is there a way to run a wire from the light fixture to the light switch? If you could replace the 12-2 cable from the fixture to the switch with 12-3, it would work just fine. All you would have to do is connect the wires a little differently than they are now, but we can get to that after the answers come in.
 
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Old 01-20-13, 05:11 AM
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more info....

So into the box I have

two feeds coming in, each contains two wires one black, one white.

only one of the blacks is hot, the other goes to the light ficture.

Current dimmer only needs neutral (white), works fine.

however, new dimmer I want to install is a new Legrand Adorne dimmer (sofTap Dimmer, 700W (Incandescent, Halogen, CFL, LED, ELV, MLV, Fluorescent) | by Legrand ), that requires a ground for the mounting plate.

The microelectronics in the switch actually test for the existance of ground and will not work without ground in existance. I have tried to fool it, and have not be able to. According to them since the switch itself pulls power for the memory, LEDs, and code it runs, it must be grounded.

Running a new ground wire requires going under the house.
Changing the wire to a 12-3 from the light requires going into the attict.

I am trying VERY hard to not go into either space =)

However (as was hopefully clear in my drawing linked again here https://twitter.com/the_solutioneer/...291712/photo/1 ) I think I can run a new 12-3 wire from a socket in the same wall that has ground, to the switch by going behind the baseboard, so I can use that 12-3 cable just for ground. I could also run just a ground wire, but I figured since the new wire will be in the wall behind the baseboard, that, it should be shielded as with a proper 12-3 cable.

Hope this makes sense, I'm a network engineer, not an Electrician =)
 
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Old 01-20-13, 07:04 AM
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Any ground you add must by code run uninterrupted back to the ground at the main panel. You can use a single conductor wire for this. You can not by code tap off a nearby ground. Code says you must only connect to the main ground within five feet of the panel.

Running a new ground wire requires going under the house.
Changing the wire to a 12-3 from the light requires going into the attict.
Why a 12-3? If you have a 12-2 now that is ungrounded replace with a 12-2 with ground. Adding another wire won't gain you anything since the extra wire can't be used as a ground. Code prohibits remarking any wire #6 or smaller as a ground. It must be a factory bare wire or factory colored green wire.

<opinion>Grounds are supposed to be non functional, for safety only to carry fault currents . They normally carry no current. Any power for the electronics should come from a neutral. I would consider it a piece of poorly designed junk and demand my money back if it requires a ground for the electronics. </opinion>
 

Last edited by ray2047; 01-20-13 at 07:24 AM.
  #5  
Old 01-20-13, 08:49 AM
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Question(s):

Is this A: Safe B: Functional C: Stupid (multiple choice)
C: Stupid - kinda. You cannot "protect" electrical cable by tucking it behind trim.

You can, however, extend a properly grounded electrical circuit.

You have four choices:
  • Run a new stand-alone ground from the panel to the switch box;
  • Replace the feed for the switch with 12-2/G or 14-2/G (depending on the breaker size) from the panel;
  • Extend the circuit from the receptacle to the switch through the wall, and abandon the existing feed;
  • Or
Originally Posted by Ray2047
<opinion>Grounds are supposed to be non functional, for safety only to carry fault currents . They normally carry no current. Any power for the electronics should come from a neutral. I would consider it a piece of poorly designed junk and demand my money back if it requires a ground for the electronics. </opinion>
BTW, welcome to the forums!
 
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Old 01-20-13, 04:38 PM
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=)

Thanks!!

A little more clarity....

I wasn't planning on using a different cable for ground, but to use a full 12/3 cable and then only use the green ground wire in the shielding to extend the ground to the switch from the grounded socket.

When I said behind baseboard, I still plan on putting it through the studs, just and the bottom behind the baseboard so I don't have to patch dry wall.

I was only using a 12/3 cable (vs 12/2) because it's what I have on hand.

I agree it's odd to require ground. The way it was explained to me was that since there are microelectronics inside the switch, that they have to require ground.

So next question:

if I can extend ground, then should I just use a single green ground wire to extend it so I avoid causing confusion for future people who may work on this house?

I was only going to use a new 12/3 line because I didn't think I could have just a single ground wiring running through studs/inside walls.
 
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Old 01-20-13, 04:43 PM
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Oh wait, just reread a post below...

"Any ground you add must by code run uninterrupted back to the ground at the main panel. You can use a single conductor wire for this. You can not by code tap off a nearby ground. Code says you must only connect to the main ground within five feet of the panel."

so then by code I can't just tap into an existing ground in the same wall.

if I have to run any cable from this switch all the way to the panel then I might as well swap out the entire line for a new one with ground.

oh well, hoped I could just do a quick fix.

Thanks so much everyone for the info!!!

great forum!!!
 
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Old 01-20-13, 05:15 PM
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Grounds are supposed to be non functional, for safety only to carry fault currents . They normally carry no current. Any power for the electronics should come from a neutral. I would consider it a piece of poorly designed junk and demand my money back if it requires a ground for the electronics.
Ray....I agree 100% ....however there are several manufacturers now that use the ground as part of the electronics. Big name brand....Watt-Stopper...uses the ground. I'm guessing that they must stay under several microamps to be able to do this under UL listing.
 
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Old 01-20-13, 06:27 PM
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Thanks PJ for the info. I wonder if requiring a neutral in the switch box will eliminate that eventually.
 
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